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Large single crystals of the solid-solution series ▪ were grown by the Czochralski method by varying the Li substitution for Na. Structure analyses with X-ray single-crystal diffraction data elucidated statistic disorder of Li with Na at three independent Na sites. The resulting Li substitution X = 0, 1.2, and 2.8 could be confirmed by neutron activation analysis. Second-harmonic generation (SHG) light intensities and non-linear optical (NLO) coefficients were determined in three crystallographic main directions by Maker fringe measurements. DFT calculations delivered absolute NLO magnitudes. UV/Vis optical spectra revealed that the transmission rises from X = 0 to X = 2.8. However, the SHG effect is at largest in ▪ (X = 1.2), so far investigated in this study. [Display omitted] • Large single crystal growth of ▪ with X = 0, 1.2 and 2.8. • Determination on Li replacing Na from single crystal X-ray diffraction and neutron activation analysis. • Large second-harmonic generation effect in ▪ with X = 1.2. [ABSTRACT FROM AUTHOR]

Deuterium insertion was used to tune the magnetic properties of Y 0.9 Tb 0.1 Fe 2 Laves phase towards an itinerant electron metamagnetic (IEM) behavior. The latter is highly sensitive to chemical changes and external parameters. The structural and magnetic properties of Y 0.9 Tb 0.1 Fe 2 D 4.3 were investigated using various neutron powder diffraction experiments in addition to magnetic measurements under steady and pulsed high magnetic fields up to 60 T. The deuteride crystallizes in a monoclinic structure (Pc space group) with 4.3 D atoms located in 18 tetrahedral interstitial sites. At zero field, it undergoes a ferrimagnetic-antiferromagnetic (FiM-AFM) transition at T M0 = 90 K, accompanied by an anisotropic magnetostriction and a negative cell volume expansion of 0.6 %. A second AFM-PM transition is observed at 146 K. Under pulsed magnetic field at 4.2 K, the deuteride displays a multistep magnetic behavior from ferrimagnetic to a ferromagnetic state, which can be attributed to a stepwise rotation of the Tb moments. The ZFC-FC magnetization curves at low fields exhibit an irreversibility below 90 K, followed by a sharp decrease in magnetization at the FM-AFM transition. Between 90 K and 130 K, the magnetization curves display an IEM behavior, with the transition field increasing linearly with temperature. Monoclinic Y 0.9 Tb 0.1 Fe 2 D 4.3 undergoes different types of metamagnetic transitions: a forced ferri-ferromagnetic transition at 4.2 K and Itinerant electron metamagnetic transitions above 90 K. [Display omitted] • Y 0.9 Tb 0.1 Fe 2 D 4. 3 crystallizes in a monoclinic structure with Pc space group. • At 4.2 K it exhibits multistep changes from ferrimagnetic to ferromagnetic states. • A FM-AFM transition occurs at 91 K with an anisotropic cell volume contraction. • Above 91 K the M (B) curves show an IEM behavior with a linear increase of B Trans. • An AFM-PM transition is observed at 146 K. [ABSTRACT FROM AUTHOR]

This study investigated the crystal structure, P–C isotherm, and cyclic properties of YNi 3. We discovered that hydrogen-induced amorphization (HIA) was appeared in three cycles of P–C isotherm at 303 K, but it was not observed at 273 K. An analysis of the three cycles at 303 K revealed a 55 % decrease in hydrogen capacity as compared to the first cycle. To enhance the hydrogenation properties, Mn was substituted for Ni. X-ray Rietveld refinements on YNi 2·7 Mn 0·3 H 3.8 reveal that the hydride phase retains the PuNi 3 -type structure of the original alloy. The values of a, c , the unit cell, the MgZn 2 -type cell, and the CaCu 5 -type cell expanded 5.6 %, 9.3 %, 21.9 %, 25.0 %, and 18.8 % from the original alloy. The results indicated that YNi 2·7 Mn 0.3 retained 91 % of its initial hydrogen capacity after three cycles at 303 K. After 120 cycles in the cyclic test, YNi 3 and YNi 2·7 Mn 0.3 retained 42 % and 90 % of their initial capacity, respectively. The XRD profile of YNi 3 after 120 absorption-desorption cycles revealed significant peak broadening. Similarly, peak broadening was also observed in the XRD profile of YNi 2·8 Mn 0.2 after 120 cycles. In comparison, the XRD profile of YNi 2·7 Mn 0.3 after 120 cycles remained relatively unchanged from its initial state. It was observed that YNi 2·7 Mn 0.3 experienced less lattice strain during hydrogenation than YNi 2·8 Mn 0.2. The retention rate of YNi 3 , YNi 2·8 Mn 0.2 and YNi 2·7 Mn 0.3 showed a moderate decrease with increasing cycles, maintaining 45 %, 62 % and 90 % at 120 cycles. [Display omitted] • Hydrogen-induced amorphization (HIA) was not observed at 273 K. • Plateau pressure decreased with increasing Mn content. • Mn substitution improved cyclic properties. • YNi 2·7 Mn 0.3 retained 90 % hydrogen capacity after 120 cycles at 303 K. • Neutron diffraction identified Mn at 6c and 18 h sites in YNi 2·7 Mn 0.3. [ABSTRACT FROM AUTHOR]

This work uses a combination of neutron diffraction and bulk property measurements to establish the low temperature magnetic states in the dense metal-organic frameworks Ho(HCO 2) 3 and Er(HCO 2) 3 ; whose structures feature chains of face-sharing Ln O 9 polyhedra packed into a triangular lattice. Below 0.7 K Ho(HCO 2) 3 is found to adopt a state in which the magnetic moment on its ferromagnetic chains vary from neighbouring chains but the sum around each triangle is constant. Er(HCO 2) 3 is found to be the first lanthanide formate to adopt an ordered magnetic state with antiferromagnetic coupling within its chains near 50 mK. The potential to combine the ferromagnetic and antiferromagnetic coupling within chains associated with Ho and Er cations, respectively, in the same compound has also been explored via the series Ho 1-x Er x (HCO 2) 3. Ho 0.5 Er 0.5 (HCO 2) 3 remains paramagnetic to 0.4 K, suggesting it may be a starting point to search for a random spin chain paramagnet. The dense metal-organic frameworksHo(HCO 2) 3 and Er(HCO 2) 3 adopt magnetic states below 1 K with ferromagnetic and antiferromagnetic order in their 1D chains, leading to an emergent charge ordered state in the former. [Display omitted] • Bulk properties and magnetic order of Ho(HCO 2) 3 and Er(HCO 2) 3 have been analysed. • Ho(HCO 2) 3 adopts an emergent charged ordered state below 0.7 K. • Ho(HCO 2) 3 and Er(HCO 2) 3 have ferromagnetic and antiferromagnetic coupled chains, respectively. • A Ho 1-x Er x (HCO 2) 3 solid solution successfully completed and characterised. • Such phases with mixed Ho and Er cations offers a route to a random spin chain paramagnet. [ABSTRACT FROM AUTHOR]

Owing to the fascinating structural and physical properties of Mn 5 Si 3 type quasibinary compounds, in this work a set of quasibinary Mn 5 Si 3 -type Gd 5 {Si, Ge} 3-x {Al, Ga} x , Gd 5 Sb 2 {Si, Bi}, Gd 5 Bi 2 Ga, Gd 5 Bi 1.8 Sn 1.2 , Tb 5 Bi 2 Sn, Tb 5 Sb 2 Bi, Dy 5 Sb 1.6-1.7 {Si, Ge} 1.4-1.3 , Dy 5 {Sb, Bi} 2 In, Dy 5 Sb 1.5 Bi 1.5 , Dy 5 Sb 1.3 Te 1.7 compounds (P 6 3 / mcm , N 193, hP 16) have been synthesized by arc melting under argon atmosphere followed by annealing between 870 and 1070 K. These compounds belong to the continuous or limited solid solutions rows of initial Mn 5 Si 3 -type binary compounds with corresponding change/distortion of initial unit cells. Neutron diffraction study in zero applied magnetic field shows sine modulated antiferromagnetic ordening of quasibinary Tb 5 Sb 2 Bi with wave vector K xx = [± K x , ± K x , 0] (K x = 0.0869–0.1356) below ∼90 K and non-collinear antiferromagnetic ordering with additional K z = [0, 0, 1/2] wave vector below ∼50 K as a representative of magnetic ordering of Tb sublattice in the Mn 5 Si 3 -type compounds. • The set of quasibinary Mn 5 Si 3 -type Gd-, Tb- and Dy-based compounds is reported. • Due to different p-elements, Tb-based compounds exhibit different magnetic structures. • At ∼90 K Tb 5 Sb 2 Bi shows HT antiferromagnetic ordering with K xx = [± K x , ± K x , 0] wave vector. • At ∼50 K Tb 5 Sb 2 Bi has ab -plane AF ordering with K xx and K z = [0, 0, 1/2] wave vectors. • This supplements the reported magnetic structures for Tb-based Mn 5 Si 3 -type compounds. [ABSTRACT FROM AUTHOR]

Conditions for YBaFe 4 O 7 synthesis from oxide/carbonate amorphous precursors are investigated versus temperature and partial pressure of oxygen at high-temperature equilibrium with the sample in flowing atmosphere of humidified Ar and H 2 gas mixtures. Upon topotactic oxidation in ambient air of the cooled-down product, YBaFeIII 4 O 8.5 forms in a couple of minutes. Neutron powder diffraction suggests that added oxygens enter octahedral holes in the cubic closest packing of O and Ba atoms of YBaFe 4 O 7. Up to two oxygen atoms add to some Fe coordination tetrahedra in the kagome-like layer of YBaFe 4 O 7 in a disordered distribution described as partially occupied crystal-structure sites. The oxidized YBaFeIII 4 O 8.5 is metastable and decomposes at high temperatures into FeIII oxides of barium or yttrium. The synthesized YBaFe 4 O 7 is a powerful room-temperature O 2 getter that can be reverted by annealing in the above gas mixture. [Display omitted] • Formation limits of YBaFe 4 O 7 under calcination of amorphous precursor. • Its topotactic oxidation in ambient air into metastable YBaFeIII 4 O 8.5 • YBaFe 4 O 7 at room temperature is a powerful O 2 gas getter. • Neutron powder diffraction of YBaFeIII 4 O 8.5 with partial oxygen disorder. [ABSTRACT FROM AUTHOR]

Sr 3 V 2 O 8 exhibits sizeable oxide ion and proton conductivity at 800 °C. In order to investigate any correlation between the crystal structure and electrical properties of Sr 3 V 2 O 8 , a variable temperature neutron diffraction study has been performed. Results show that there is no change in crystal symmetry upon heating. However, the VO 4 tetrahedra are observed to become more distorted upon heating and more oblate in shape. The distortion arises due to a shortening of the apical V–O1 bond length and accompanying increase of the V–O2 bond length with temperature. Bond valence site energy analysis show that there is a reduction in the energy of the migration pathways for movement of the oxide ions as the Sr–V–Sr bottlenecks expand upon heating. A variable temperature neutron diffraction study of the palmierite Sr 3 V 2 O 8 shows there is an increase in the distortion of the VO 4 tetrahedra with temperature. There is also an expansion of the Sr–V–Sr bottlenecks which may enhance the oxide conductivity upon heating. [Display omitted] • A variable temperature neutron diffraction study of the dual ion conductor Sr 3 V 2 O 8 has been performed. • Results show no change in crystal symmetry on heating. • The VO 4 tetrahedra become more distorted with temperature. • Bond valence site energy calculations show there is an expansion of the Sr–V–Sr bottlenecks upon heating. • Chemical substitutions that further expand the Sr–V–Sr bottlenecks provide a route to optimise the ionic conductivity. [ABSTRACT FROM AUTHOR]

We have investigated the crystal structure and electrical properties of Bi 3 GaSb 2 O 11 at high temperatures. Neither phase transitions nor change in oxygen content were observed at 26–800 °C in air. The crystal structure was successfully refined using neutron diffraction data taken at 26–600 °C. The average thermal expansion coefficient between 26 and 600 °C was 10.4614(7) × 10‒6 °C‒1. There are three different (Ga/Sb)–O bonds of (Ga/Sb)–O3b, (Ga/Sb)–O2, and (Ga/Sb)–O3a. It was found that the thermal expansion coefficient of the (Ga/Sb)–O3b bond is lower than those of other bonds. At 916 °C the total DC electrical conductivity in N 2 (1.4 × 10‒3 S cm‒1) was higher than that in air (7.1 × 10‒4 S cm‒1), due to electron conduction in N 2. In air, oxide-ion conduction was suggested by electrical-conductivity and polarization measurements. Bond-valence-based-energy calculations suggested oxide-ion migration along the O–O edges and on O–O–O faces of (Ga/Sb)O 6 octahedra. Crystal structure of Bi 3 GaSb 2 O 11 was refined by neutron diffraction at 26–600 °C. Electrical conductivity of Bi 3 GaSb 2 O 11 increases with temperature at 582–893 °C. [Display omitted] • Bi 3 GaSb 2 O 11 exhibits neither phase transitions nor composition change at 26–800 °C. • Electrical conductivity of Bi 3 GaSb 2 O 11 increases with temperature at 582–893 °C. • Crystal structure of Bi 3 GaSb 2 O 11 was refined by neutron diffraction at 26–600 °C. • Distortion index of the (Ga/Sb)O 6 increases with increasing temperature. • Oxide-ion conduction of Bi 3 GaSb 2 O 11 was suggested at 916 °C in air. [ABSTRACT FROM AUTHOR]

Ba 2 CaMoO 6 was synthesized by a solid state method. The crystal structure adopts the cubic Fm -3 m space group at room temperature with lattice parameters of 8.3775 (9) Å. Upon cooling, Ba 2 CaMoO 6 was determined to have a structural phase transition to tetragonal I 4/ m (a = 5.9051 (2) Å and c = 8.3872 (4) Å) near 200 K. The phase transition was probed structurally by synchrotron and neutron diffraction and thermodynamically by specific heat and differential scanning calorimetry measurements. This structural phase transition will deepen our understanding of the perovskite family, especially the formation of perovskites that break corner sharing networks. Image 1 • Ba 2 CaMoO 6 adopts cubic Fm -3 m space group at room temperature. • Ba 2 CaMoO 6 adopts tetragonal I 4/ m at temperatures below 200 K. • Cooperative octahedra tilted perovskite formation favored in this system. [ABSTRACT FROM AUTHOR]

The manganese endmember of hureaulite (Mn-hureaulite, Mn2+ 5 (PO 4) 2 (PO 3 (OH)) 2 (HOH) 4 with a minor trace of Sr2+) was synthesized under various hydrothermal conditions to yield high-quality crystals up to 1 mm in length. The deuterated samples were investigated using high-resolution neutron powder diffraction (HRNPD) at 12 K and 298 K to understand the proton conductivity in the context of dynamically disordered hydrogen bond networks (DDHBN). Results from Rietveld analysis on HRNPD data combined with bond valence sum (BVS) mismatch landscapes and maximum-entropy methods (MEM) revealed protonic motions confined by two semihelical chains as a DDHBN within 8-membered ring channels running along the crystallographic c axis. A DC bulk conductivity value of 4.5x10-5 Scm-1 at 498 K was evaluated from the high-frequency (HF) relaxation mode in impedance spectroscopy (IS) of Mn-hureaulite powder samples. IS spectra acquired at 398-498 K were fitted to two serially connected RC-circuits, equivalent to inter- and intragrain charge transport. A low activation energy of 0.31(3) eV between 398 K and 473 K indicates the ease of site-exchanging protons over DDHBN in the title compound. Isosurfaces around D sites (in blue) with threshold at 0.6 v.u. evaluated from BVS calculations with RT HRNPD data indicate possible path ways for the protonic conductivity in Mn-hureaulite. Image 1 • The protonic motions in a hureaulite-type compound, Mn2+ 5 (PO 4) 2 (PO 3 (OH)) 2 (DOD) 4. • Proton motions over dynamically disordered hydrogen bonded two semihelical chains. • A low activation energy of 0.31(3) eV for site-exchanging protons. [ABSTRACT FROM AUTHOR]

A tetragonal oxyfluoride Ba 2 SrGaO 4 F, a novel material in the Sr 3 AlO 4 F family of materials, has been synthesized via solid-state method and exhibits self-activated photoluminescence (PL) under 254 nm light after annealing in a reducing atmosphere of 4%H 2 /96% Ar. The structure of this material is determined by powder x-ray diffraction and confirmed using high-resolution neutron powder diffraction, which reveals similarities to Sr 3 AlO 4 F-type oxyfluorides and Ba 2 GaLaO 5. Analysis of the refined Ba 2 SrGaO 4 F structure at room temperature reveals subtle changes in the polyhedral sub-units between the reductively annealed and air-annealed samples, which are correlated with the PL emission. The structure of the novel oxyfluoride Ba 2 SrGaO 4 F is studied at room temperature. The structure can be viewed as alternating layers of compression and elongation of polyhedral subunits based on the bond valence sum values. Image 1 • The novel oxyfluoride, Ba 2 SrGaO 4 F, is synthesized via solid-state method. • Ba 2 SrGaO 4 F exhibits broad-band photoluminescence when annealed in a 4%H 2 /96% Ar atmosphere. • High-resolution neutron diffraction is used to analyze changes between air and reductively annealed samples of Ba 2 SrGaO 4 F. [ABSTRACT FROM AUTHOR]

La 3 Ni 2- x Cu x B 'O 9 (x = 0.25; B ' = Sb, Ta, Nb: x = 0.5; B ' = Nb) have been synthesized and characterised by transmission electron microscopy, neutron diffraction and magnetometry. Each adopts a perovskite-like structure (space group P 2 1 / n) with two crystallographically-distinct six-coordinate sites, one occupied by a disordered arrangement of Ni2+ and Cu2+ and the other by a disordered ∼1:2 distribution of Ni2+ and B ′5+, although some Cu2+ is found on the latter site when x = 0.5. Each composition undergoes a magnetic transition in the range 90 ≤ T /K ≤ 130 and shows a spontaneous magnetisation at 5 K; the transition temperature always exceeds that of the x = 0 composition by ≥ 30 K. A long-range ordered G-type ferrimagnetic structure is present in each composition, but small relaxor domains are also present. This contrasts with the pure relaxor and spin-glass behaviour of x = 0, B ' = Ta, Nb, respectively. Image 1 • Substitution of S = 1 Ni2+ by S = ½ Cu2+ enhances magnetic ordering. • HR-EDX establishes nature of cation ordering in a complex perovskite solid solution. • Neutron diffraction identifies long-range magnetic ordering. [ABSTRACT FROM AUTHOR]

Heusler composites have attracted significant attention as a new route towards improving the thermoelectric figure of merit (ZT) through reduction of the lattice thermal conductivity and carrier filtering effects. This work extends this field by investigating TiCoSb-TiM 2 Sn (M = Ni, Fe) composites. All end-members are stable phases but no clean segregation into half- and full-Heusler phases was observed. Instead, for M = Ni, partial substitution on the Co sublattice and n-type doping occurs, combined with the formation of Ni 3 Sn 2 and full-Heusler phases. For M = Fe, substitution on the Co site occurs, leading to p-type conduction. Rietveld analysis of neutron powder diffraction data reveals no evidence for the presence of metals on the vacant tetrahedral site, signalling the absence of embedded Heusler inclusions. The thermoelectric properties of both series vary systematically with composition. For both n-type (M = Ni) and p-type (M = Fe) series, the highest measured power factors S2/ρ ∼ 0.8 mW m−1 K−2 leading to ZT ∼ 0.12 at 713 K. This work extends knowledge regarding the phase stability and thermoelectric properties of TiCoSb-based Heusler composites. The structures and thermoelectric properties of TiCoSb - TiM 2 Sn (M = Fe, Ni) Heusler composites have been investigated. Image 1 • TiCoSb - TiM 2 Sn (M = Fe, Ni) Heusler composites explored. • No evidence for embedded Heusler inclusions or interstitial metals. • Only direct Fe and Ni substitution occurs with maximum ZT = 0.12 at 713 K. [ABSTRACT FROM AUTHOR]

Bi 2 TeO 5 has been obtained in polycrystalline form via solid state reaction and structurally characterized from both synchrotron and neutron powder diffraction data, enabling the precise determination of the atomic positions. The crystal structure is defined in the acentric Amb 2 space group, containing three crystallographically unequivalent Bi atoms. The position of the stereochemically active electron lone pairs of both Bi3+ and Te4+ ions is inferred to be opposite to the strongly covalent Bi O and Te O chemical bonds; the global electron polarization arises from the non-compensated Bi3+ lone electron pairs. Additionally, from difference Fourier maps between synchrotron and neutron diffraction data (X-N technique) it was possible to observe experimental evidence of the lone electron pair for Bi3+. Nonlinear optical measurements display highly active second harmonic generation response, comparable to that of reference AgGaSe 2. Image 1 • The crystal structure is defined in the non-centrosymmetric Amb 2 space group. • Fourier maps between synchrotron and neutron diffraction data (X-N technique). • Experimental evidence of Bi3+lone electron pair from X-N study. • Nonlinear optical measurements display highly active SHG response. [ABSTRACT FROM AUTHOR]

TiO 2 :MoO 3 nanocomposites with MoO 3 content in the range of 0.1–10 mol.% were synthesized using sol-gel technology. The role of the structural peculiarities of TiO 2 :MoO 3 composite in hydrogen adsorption and catalytic oxidation was discussed. Possibility of the selective oxidation of hydrogen in the presence of methane in the atmosphere was demonstrated. Image 1 • H 2 adsorption and oxidation on TiO 2 :MoO 3 nanocomposites were investigated. • H 2 adsorption takes place on (Mo-O)5+ and [(Mo O)3+-(O2−) 3 ] centers. • H 2 oxidation occurs by MoO 3 lattice oxygen and adsorbed O 2 − species. • TiO 2 :MoO 3 composite is a prospective gas sensing material for H 2 selective detection. [ABSTRACT FROM AUTHOR]

The Ruddlesden-Popper phase LaSr 3 Fe 3 O 10 and its reduced derivatives with nominal composition LaSr 3 Fe 3 O 10– x , with 0 < x < 1.21, are described in detail with respect to crystal structure, magnetic order, thermal stability and likely vacancy mechanisms. The crystal structure of the LaSr 3 Fe 3 O 9 (x = 1) phase is described. The LaSr 3 Fe 3 O 10-δ phase prevails for x < 0.51, whereas LaSr 3 Fe 3 O 9± ε prevails for x > 0.85. The phases are separated by a two-phase region 0.51 < x < 0.85. By combined Rietveld refinements of high-resolution powder synchrotron and neutron diffraction, the crystallographic and magnetic structure of LaSr 3 Fe 3 O 9 is described. LaSr 3 Fe 3 O 9 takes a layer like RP3 type structure with features of the brownmillerite structure in the triple perovskite type slabs; unit cell dimensions a = 28.7562(13) Å, b = 5.5280(2) Å, c = 5.4583(2) Å, space group Cmcm. LaSr 3 Fe 3 O 9 is an antiferromagnet with T N > 350 K and with a G-type magnetic structure, magnetic space group P C bcm. Based on unit cell volume considerations, local oxygen vacancy ordering schemes are suggested. Crystal- (left) and magnetic structure (right) of LaSr 3 Fe 3 O 9. Image 1 • LaSr 3 Fe 3 O 9 is described as a Ruddlesden-Popper – brownmillerite hybrid. • Reversible incorporation and removal of oxygen in the lattice, LaSr 3 Fe 3 O 10- x. • LaSr 3 Fe 3 O 9 goes by a two-phase region (0.51 < x < 0.85) to LaSr 3 Fe 3 O 10. • LaSr 3 Fe 3 O 9 is described as a G-type antiferromagnet. [ABSTRACT FROM AUTHOR]

Abstract Neutron diffraction experiments conducted at 5 K in a magnetic field 0 ≤ H /kOe ≤50 have shown that the monoclinic perovskite La 3 Ni 2 TaO 9 behaves as a relaxor ferromagnet. Compositions in the series La 3 Ni 2 Sb x Ta y Nb 1– x – y O 9 have been synthesized in polycrystalline form. Electron microscopy, X–ray diffraction and neutron diffraction have shown that the solid solutions are largely homogeneous and monophasic. Magnetometry and neutron diffraction have shown that the relaxor magnetisation persists in low fields when x + y = 1 but is rapidly diminished by the introduction of niobium. This change in magnetic behaviour is ascribed to the differences in the d –orbital energies of Sb5+, Nb5+ and Ta5+. Graphical abstract Magnetic properties of La 3 Ni 2 Sb x Ta y Nb 1-x-y O 9 are sensitive to the relative concentration of different pentavalent cations. Image 1 Highlights • In-field neutron diffraction shows La 3 Ni 2 SbO 9 to be a relaxor ferromagnet. • HR-EDX establishes nature of cation ordering in a complex perovskite solid solution. • Ta5+ and Sb5+ support relaxor ferromagnetism; Nb5+ does not. • Difference in magnetic properties of Nb- and Ta-containing perovskites is attributable to electronic factors. [ABSTRACT FROM AUTHOR]

Abstract Magnetic ordering of the polycrystalline Lu 14 Ni 3 In 3 -type Gd 14 Ni 3 Al 3 and Tb 14 Ni 3 Al 3 (space group P 4 2 / nmc , N 137, tP 80) has been studied by magnetization, heat capacity and neutron diffraction study. The magnetization and heat capacity measurements of Gd 14 Ni 3 Al 3 reveal the antiferromagnetic ordering at 62 K and low-temperature spin-reorientation transition at 42 K. Neutron diffraction study in zero applied magnetic field indicates non-collinear antiferromagnetic ordering of Tb 14 Ni 3 Al 3. It exhibits abc -antiferromagnetic ordering with magnetic space group P2 1 ′/c′ (wave vector K 0 = [0, 0, 0]) below 47 K and slight reorientation of terbium magnetic moments between 16 K and 36 K. Graphical abstract Image 1 Highlights • {Gd, Tb} 14 Ni 3 Al 3 demonstrate pure antiferromagnetic ordering. • Gd 14 Ni 3 Al 3 exhibits antiferromagnetic transitions at T N = 62 K and T m = 42 K. • Gd 14 Ni 3 Al 3 shows field induced weak ferromagnetism. • Tb 14 Ni 3 Al 3 exhibits abc -AF ordering with wave vector K 0 = [0, 0, 0] in zero field. • abc -AF ordering of Tb 14 Ni 3 Al 3 meets to magnetic space group P2 1 ′/c′. [ABSTRACT FROM AUTHOR]

Abstract Li 2 O-Al 2 O 3 -GeO 2 -P 2 O 5 (LAGP) glass ceramics (GC) has potential for use as solid state electrolyte in Li-ion rechargeable batteries with better safety and thermal stability. In this work LAGP glass-ceramics with nominal composition of Li 1.5 Al 0.5 Ge 1.5 P 2.9 Si 0.1 O 12 , have been prepared and structural studies have been carried out to understand the effect of Al3+ and Si4+substitution in place of Ge4+ and P5+. Glass was prepared using melt quenching technique and converted into glass-ceramics by controlled heat treatment. We observed that the entire glass has changed in to crystalline form. Phase formation was confirmed using XRD (X-ray diffraction) and ND (Neutron diffraction). Rietveld refinement analysis was used for structural analysis using both ND and XRD data. Analysis showed better refinement in ND and the nuclear density information of two different positions of Li+ ion (M1&M2) was revealed from Fourier maps using ND data. This helps to predict the pathway of Li diffusion in the structural units and optimize the conductivity of material. Results showed expansion of c-axis and reduction of a-axis with substitution of Al3+ in place of Ge+4. Bottleneck for Li+ ion conduction found to increase making an easier path for conduction. The study was further correlated from the recorded local structural data using X-ray photoelectron spectroscopy and Raman Spectroscopy. Graphical abstract Experimental (•) and calculated (-) neutron diffraction pattern of LAGP1 and close view of the positions of Li1, Li2 and the GeO 6 octahedra and PO 4 tetrahedra obtained from refinement. fx1 Highlights • Substitution of Al expands the bottleneck thus increases ionic conduction in LAGP. • Nuclear charge density around two different Li+ ion (M1&M2)was simulated from Fourier maps using ND data. • XPS also confirm the presence of two Li peak corresponding to M1 and M2 sites. [ABSTRACT FROM AUTHOR]

Abstract This work details a comparative investigation within the system Zn 2.5 − x A ′ x VMoO 8 (A ′ 2 + = Mn, Ni, Cu). Samples were prepared between 700 and 1000 °C, resulting in various colors. All three solid solutions were found to exhibit a miscibility gap before or at the midpoint, beyond which phase separation occurs. X-ray and neutron powder diffraction were used to elucidate the cause of these solubility limits and diffuse reflectance measurements revealed varying color mechanisms. All phase pure members of the solid solutions are found to be similar to the parent compound, and magnetic susceptibility measurements confirmed the +2 oxidation state for all substitutions, with tendency towards antiferromagnetic exchange as x increases. Graphical abstract Partial solubility was observed for Zn 2.5 − x A ′ x VMoO 8 (A ' 2 + = Mn, Ni, Cu), caused by chemical-dependent factors, while also yielding unexpected colors (arising from coexisting excitation mechanisms). fx1 Highlights • Novel lyonsite solid solutions were prepared via A-site substitution. • Full solubility was prevented by reasons unique to each substituent. • Site disorder prevents long-range antiferromagnetic ordering. • Unexpected yellow colors are promising for inorganic road paints. [ABSTRACT FROM AUTHOR]

Abstract Polycrystalline samples of Gd 2 CaGe 4 O 12 and GdFeZnGe 4 O 12 have been synthesised via a ceramic route. Both were characterised by X-ray diffraction, magnetometry and Mössbauer spectroscopy; GdFeZnGe 4 O 12 was also studied by neutron diffraction. They adopt the SrNa 2 P 4 O 12 structure: space group P 4/ nbm with a = 10.0766(1), c = 5.1043(1) Å for Gd 2 CaGe 4 O 12 ; a = 9.7298(1), c = 4.7515(1) Å for GdFeZnGe 4 O 12 at 293 K. Gd 2 CaGe 4 O 12 is paramagnetic for 2 ≤ T/K ≤ 300 whereas GdFeZnGe 4 O 12 is antiferromagnetic below 13.8(2) K. The six-coordinate Fe3+ and Zn2+ cations are disordered over the pseudo-cubic 4 f sublattice and the Gd3+ cations occupy the eight-coordinate 2 b sites. The Fe3+ and Gd3+ cations adopt an A-type, k = [0,0,½] antiferromagnetic arrangement with their ordered moments aligning in the xy plane. The Fe/Zn disorder results in relatively low ordered cation moments (Gd3+ = 6.02(13), Fe3+ = 3.84(15) µ B) in the antiferromagnetic phase. Graphical abstract A study of antiferromagnetic GdFeZnGe 4 O 12 and paramagnetic Gd 2 CaGe 4 O 12 involving neutron diffraction and both 57Fe and 155Gd Mössbauer spectroscopy. fx1 Highlights • Neutron diffraction study of a gadolinium compound. • 57Fe and 155Gd Mössbauer spectroscopy applied to the same compound. • Magnetic order of Gd3+ cations at 13.8 K. [ABSTRACT FROM AUTHOR]

Abstract Polycrystalline samples of the new perovskites SrLaCrSnO 6 and Ca 2 CeCr 2 TiO 9 have been synthesised using the ceramic method and characterized by x-ray diffraction, neutron diffraction and magnetometry. Both crystallise in the space group Pbnm , with a disordered distribution of B-site cations, and both exhibit G z -type antiferromagnetism at low temperatures. The antiferromagnetic order develops over a large temperature range. It is proposed that isolated antiferromagnetic clusters grow in size upon cooling to form a long-range antiferromagnetically-ordered backbone running through the structure. Cations with few magnetic nearest-neighbours remain decoupled from the backbone down to 2 K. More decoupled clusters are present in Ca 2 CeCr 2 TiO 9 than in SrLaCrSnO 6. This is attributed to the increase in frustration that accompanies the increase in strength of the next-nearest-neighbour interactions that occurs when d 10:Sn4+ is replaced by d 0:Ti4+. Graphical abstract The ZFC and FC molar dc susceptibility of a) SrLaCrSnO 6 and b) Ca 2 CeCr 2 TiO 9 measured in an applied field of 100 Oe as a function of temperature. The inset shows the inverse molar dc susceptibility fitted to the Curie-Weiss law. fx1 [ABSTRACT FROM AUTHOR]

Abstract Neutron diffraction measurements of the double molybdate Cs 3 Na(MoO 4) 2 have been performed for the first time in this work and the crystal structure refined using the Rietveld method. The thermal expansion of this trigonal phase, in space group P 3 ¯ m 1 , measured using high temperature X-ray diffraction (XRD), remains moderate: α a = 31 · 10 − 6 K − 1 and α c = 24 · 10 − 6 K − 1 in the temperature range T = (298−723) K. The melting temperature of this compound has been determined at T fus = (777 ± 5) K using Differential Scanning Calorimetry (DSC). No phase transition was detected, neither by DSC, nor by high temperature XRD or high temperature Raman spectroscopy, which disagrees with the literature data of Zolotova et al. (2016), who reported a reversible phase transition around 663 K. Finally, thermodynamic equilibrium calculations have been performed to assess the probability of formation of Cs 3 Na(MoO 4) 2 inside the fuel pin of a Sodium cooled Fast Reactor by reaction between the cesium molybdate phase Cs 2 MoO 4 , which forms at the pellet rim at high burnup, the fission product molybdenum (either as metallic or oxide phase), and the liquid sodium coolant in the accidental event of a breach of the stainless steel cladding and sodium ingress in the failed pin. Graphical abstract The structural and thermodynamic properties of Cs 3 Na(MoO 4) 2 have been investigated by neutron diffraction, high temperature X-ray diffraction, high temperature Raman spectroscopy, and Differential Scanning Calorimetry. The oxygen potential threshold for the formation of Cs 3 Na(MoO 4) 2 in the event of ingress of sodium in a failed nuclear fuel pin has been assessed. fx1 Highlights • The structure of trigonal Cs 3 Na(MoO 4) 2 has been refined from neutron diffraction data. • The thermal expansion of Cs 3 Na(MoO 4) 2 has been measured using high-temperature XRD. • No phase transition was detected around 663 K neither by DSC, XRD or Raman data. • The oxygen potential threshold to form Cs 3 Na(MoO 4) 2 in liquid sodium was evaluated. • 0.25 wppm oxygen dissolved in Na(l) are sufficient at 900 K to form Cs 3 Na(MoO 4) 2. [ABSTRACT FROM AUTHOR]

Abstract Polycrystalline ErFeCuGe 4 O 12 has been prepared in a solid-state reaction. It adopts a tetragonal crystal structure; space group P 4/ nbm with a = 9.6416(1), c = 4.7532(1) at room temperature. The Er3+ cations are in square-antiprismatic coordination and the Fe3+ and Cu2+ cations are disordered over one six-coordinate site. The magnetic moments of the three cations adopt an antiferromagnetic arrangement on cooling below 20 K in H = 0 kOe. The magnetic structure consists of ferromagnetic (001) sheets with the spin direction in neighbouring sheets alternating between [001] and [00 1 ̅ ] At 5 K the ordered moment of Er3+ was determined by neutron diffraction to be 7.90(3) µ B and the mean moment of Fe3+ and Cu2+ was 2.43(2) µ B. The magnetic structure is unchanged in an applied field of 10 kOe but in fields ≥ 20 kOe the compound begins a metamagnetic transition to a ferromagnetic structure with all atomic moments aligned along [001]. Graphical abstract At 2 K, antiferromagnetic ErFeCuGe 4 O 12 undergoes a metamagnetic transition to a ferromagnetic state in an applied magnetic field of ≥ 20 kOe. fx1 Highlights • Antiferromagnetic ordering in mixed 4 f /3 d system. • Metamagnetic transition to ferromagnetic state. • Neutron diffraction in an applied field. [ABSTRACT FROM AUTHOR]

Abstract Polycrystalline samples of the perovskites Ca 2 PrCr 2 B O 9 (B = Nb, Ta) have been synthesised using the standard ceramic method and characterized by x-ray diffraction, neutron diffraction and magnetometry. Both crystallise in the orthorhombic space group Pnma and exhibit magnetisation reversal when field-cooled in an applied field of 100 Oe. The absolute value of the negative magnetisation at 2 K in an applied field of 100 Oe is an order of magnitude greater in Ca 2 PrCr 2 TaO 9 than it is for Ca 2 PrCr 2 NbO 9. Magnetometry and powder neutron diffraction showed that the Cr3+ cations in Ca 2 PrCr 2 NbO 9 and Ca 2 PrCr 2 TaO 9 order in a G y F z magnetic structure below 110 and 130 K, respectively. The Pr3+ cations remain paramagnetic down to ~ 10 K and show no-long range order at 2 K. Both compounds show a large degree of hysteresis in M (H), with coercive fields of 3.79 kOe and 3.03 kOe at 2 K. Graphical abstract The FC molar dc susceptibility as a function of temperature measured on warming after cooling in applied fields of 0.1 (red), 1 (orange) 3 (green) and 10 kOe (purple) for a) Ca 2 PrCr 2 NbO 9 and b) Ca 2 PrCr 2 TaO 9. fx1 Highlights • Field dependent magnetisation reversal. • Canted antiferromagnetic G y F z magnetic structure. • Polarisation of paramagnetic Pr3+ moment by negative internal field. [ABSTRACT FROM AUTHOR]

α-titanium phosphate phase [α-Ti(HPO 4) 2 ·H 2 O; abbreviated as α-TiP] is a nanolayered metal phosphate with several industrial and recent biotechnological applications related to their nanolayered morphology and ion exchange capabilities. Structural wise, α-TiP is a tetravalent metal phosphate that tends to crystallize into microcrystalline powder. Here we report that the crystallization of single α-TiP crystals with suitable dimensions (>50 μm) for single-crystal X-ray diffraction could be effectuated using a prolonged hydrothermal treatment of a metallic titanium alloy (Ti–6Al–4V) in a highly concentrated phosphoric acid aqueous solution. Accordingly, the single-crystal X-ray diffraction analysis revealed the crystalline structure in a monoclinic space group, P2 1 /c, with a = 8.6288(5) Å, b = 5.00546(17) Å, c = 19.1468(11) Å, and β = 127.555(9)°. Although the space group is the same crystallographic space group that was previously reported from the microcrystalline powder relying on powder X-ray diffraction (PXRD) and neutron powder diffraction, the obtained unit cell volume is slightly larger. Bulk of the obtained crystals were also subjected to detailed analyses using polarization optical microscopy (POM), scanning electron microscopy combined with energy dispersive X-ray microanalysis (SEM-EDX), Fourier transform Infrared Spectroscopy (FTIR) and thermal analysis (TG/SDTA). The single crystals are hexagonally shaped and exhibit the exact titanium to phosphorus ratio expected for α-TiP. The bulk sample PXRD pattern resembles perfectly that reported for the α-TiP polycrystalline powder with clearly sharper peaks. TGA-SDTA analysis revealed the expected thermal behaviour for α-TiP phase and demonstrated their higher thermal stability when compared to the polycrystalline powder. [Display omitted] • A new approach to grow single crystals of α-Ti(HPO 4) 2 ·H 2 O, usually obtained as crystalline powder is reported. • The grown single crystals are big enough for several microscopic and single X-ray crystallography analyses. • The obtained single crystal structure is a 0.6% expanded version of that previously determined using the polycrystalline powder. • The single crystals exhibit higher thermal stability compared to the polycrystalline powder. • The research findings present a base for other metal phosphates that have been only investigated as polycrystalline powder. [ABSTRACT FROM AUTHOR]

Herein, the high-pressure/high-temperature synthesis (11 GPa, 650 °C) of Tb 3 B 10 O 17 (OH) 5 in a modified Walker-type multianvil device is presented. The structure of this rare-earth borate was determined by single-crystal X-ray diffraction methods and was found to crystallize orthorhombically in the space group Pmn 2 1 (no. 31) with the unit cell parameters a = 16.2527(4), b = 4.4373(1), and c = 8.8174(2) Å. The new compound was further characterized using infrared spectroscopy, energy-dispersive X-ray spectroscopy, second harmonic generation (SHG) measurements, and temperature-dependent X-ray powder diffraction. Tb 3 B 10 O 17 (OH) 5 decomposes to β -Tb(BO 2) 3 at temperatures higher than 460 °C. With increasing temperatures, the formation of μ -TbBO 3 was observed, which transforms to π -TbBO 3 upon cooling. The hydroxyl-containing terbium borate Tb 3 B 10 O 17 (OH) 5 was synthesized under high-pressure conditions in a Walker-type multianvil device at 11 GPa and 650 °C. The new compound was found to crystallize in the orthorhombic space group Pmn 2 1 (no. 31) with the unit cell parameters a = 16.2527(4), b = 4.4373(1), c = 8.8174(2) Å, and two formula units per cell by single-crystal diffraction methods. Tb 3 B 10 O 17 (OH) 5 was further characterized using infrared spectroscopy, energy-dispersive X-ray spectroscopy, second harmonic generation (SHG) measurements, and temperature-dependent X-ray powder diffraction. Tb 3 B 10 O 17 (OH) 5 decomposes to β -Tb(BO 2) 3 at temperatures higher than 460 °C. With increasing temperature, the formation of μ -TbBO 3 was observed, which transforms to π -TbBO 3 upon cooling. [Display omitted] • Tb 3 B 10 O 17 (OH) 5 was synthesized at 11 GPa and 650 °C in a Walker-type multianvil device. • Tb 3 B 10 O 17 (OH) 5 crystallizes non-centrosymmetrically in the orthorhombic crystal system. • Tb 3 B 10 O 17 (OH) 5 is stable up to 460 °C. • Above 460 °C, the formation of β -Tb(BO 2) 3 is observed, which further decomposes to μ -TbBO 3. • Upon cooling, μ -TbBO 3 transforms to π -TbBO 3. [ABSTRACT FROM AUTHOR]

Abstract A binary phosphorus telluride sample (20 at% Te) was synthesized by mechanochemical solid state reaction from elemental powders. The X-ray diffraction pattern and neutron total structure factor show no detectable Bragg peaks, indicating that the sample is amorphous with respect to X-ray and neutron diffraction. The neutron and X-ray total pair distribution functions show correlation peak arising from P Te heteropolar bonds in addition to those arising from P P and Te Te bonds. The Te Te bond length is slightly shorter than that in the crystal structure of trigonal tellurium, suggesting a different environment from a polymeric chain structure. The thermal analysis results show that the binary phosphorus telluride is thermally unstable, that is, it decomposes above 200 °C into trigonal tellurium crystals and gaseous phosphorus, where phosphors begins to gasify at a lower temperature than the sublimation temperature of red phosphors. Graphical abstract The neutron and X-ray total structure factors and total pair distribution functions of P 0.8 Te 0.2 sample are shown. The blue, green and red lines respectively represent Gaussian peaks for P P, P Te and Te Te pairs. fx1 [ABSTRACT FROM AUTHOR]

The lyonsites are an underexplored crystal structure type; with precedent for compositional flexibility, this family of compounds has potential uses as inexpensive functional materials. This work examines cationic substitutions into Zn 2.5 − x Co x VMoO 8 and the subsequent effect on the Zn site preference. All samples were annealed between 700 and 1000 °C, resulting in green-colored pastilles. Powder X-ray diffraction (PXRD) and neutron powder diffraction (NPD) confirmed the solid solution range to be 0 ≤ x ≤ 2.5, with all members isostructural with the parent compound. Magnetic susceptibility measurements indicated Curie-Weiss behavior in the high T region, confirming the presence of Co(II). Diffuse reflectance measurements are also presented to explain the color mechanisms of this series. [ABSTRACT FROM AUTHOR]

Crystal structure and magnetic properties of glaserite-type Ba 3 MnSi 2 O 8 were investigated using variable temperature neutron powder diffraction and magnetometry. At room temperature the composition is hexagonal and the crystal structure is best described by the P -3 m 1 space group (a~ 5.7 Å, c~ 7.3 Å) with the apical oxygen atom modelled on a split site. On cooling below ~ 250 K the structure undergoes a phase transition into a monoclinic C 2/ c form (√3a hex , a hex , 2c hex , β~ 90°). Analysing diffraction data in terms of symmetry-adapted distortion modes suggests that the transition is primarily driven by increasing in-plane displacements of O1, which in turn results in the coupled tilting of [SiO 4 ] and [MnO 6 ] octahedra and in-plane displacements of Ba1 atoms. Magnetic susceptibility measurements and neutron powder diffraction data show no evidence for long-range magnetic ordering down to 1.6 K, although the development of magnetic diffuse scattering suggests that a magnetic transition may take place at lower temperature. [ABSTRACT FROM AUTHOR]

Abstract A study of the solid solutions Ce M 2-x M’ x Ge 4 O 12 ( M = Mn, Co; M’ = Ni, Cu) by X-ray diffraction and magnetometry is described. For M = Co the introduction of Ni and Cu was possible for x ≤ 0.5; for M = Mn attempts to introduce Cu were unsuccessful but CeMn 1.5 Ni 0.5 GeO 4 was obtained as a single phase. These compositions crystallise in the space group P 4/ nbm with a ~9.76, c ~4.85 Å. They all order antiferromagnetically with T N < 10 K. The magnetic structures adopted by CeMn 1.5 Ni 1.5 Ge 4 O 12 and CeCo 1.5 Cu 0.5 Ge 4 O 12 were shown by neutron diffraction to be the same as those adopted by CeMn 2 Ge 4 O 12 and CeCo 2 Ge 4 O 12 , respectively. The in-field metamagnetic transition of the latter to a weakly ferromagnetic phase was shown to persist in the Cu-doped composition. The available data suggest that the anisotropy associated with the Co2+ cation plays a dominant role in determining the magnetic behaviour of these compounds. Graphical abstract The magnetic structure of germanate solid solutions is a function of composition and applied field. fx1 Highlights • marked composition dependence of magnetic structure. • metamagnetic transition in CeCo 1.5 Cu 0.5 Ge 4 O 12. • neutron diffraction in an applied field. [ABSTRACT FROM AUTHOR]

Abstract We present an in-depth study on the structure and magnetic properties of a novel layered oxide, Ca 2 Fe 0.875 Cr 0.125 GaO 5. Structural studies from laboratory X-ray diffraction, synchrotron powder X-ray diffraction and neutron powder diffraction reveal that the compound crystallizes in an orthorhombic Brownmillerite phase with Pnma space group having Fe/Cr – octahedral layers and Ga – tetrahedral layers with around 9.0% of Fe occupying tetrahedral sites. The temperature evolution of Neutron powder diffraction confirms the absence of any structural changes in the range 300–6 K. Magnetic characterizations show antiferromagnetic ordering at room temperature and the co-existence of antiferromagnetic and ferromagnetic phases at low temperature. The magnetic structure derived from neutron powder diffraction is a G -type antiferromagnetic. The ordered magnetic moments at 6 K on the octahedral and tetrahedral sites are 3.15 (2) µ B /cation and 0.93 (4) µ B /cation, respectively oriented in the ac -plane. Graphical abstract Rietveld refined X-ray diffraction pattern at 300 K and magnetic structure obtained from Neutron diffraction at 6 K for Ca 2 Fe 0.875 Cr 0.125 GaO 5 fx1 Highlights • Crystal and magnetic structure of Ca 2 Fe 0.0875 Cr 0.125 GaO 5 was studied thoroughly. • Compound possesses orthorhombic Pnma space group. • ∼ 9% of Fe/Ga disorder between the Fe/Cr – octahedral and Ga –tetrahedral layers. • Magnetic structure is found to be G-type antiferromagnetic. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of compositions in the perovskite solid solution Sr 2- x Ca x CrSbO 6 ( x  = 0, 0.25. 0.5, 0.75, 1.0, 1.25, 1.50, 1.75, 2.0) were synthesised and characterised by synchrotron x-ray diffraction and SQUID magnetometry. Neutron powder diffraction data were collected on the x  = 0, 0.25, 0.5, 1.0, 1.5 and 2.0 compositions. It was found that Sr 2 CrSbO 6 crystallised in the triclinic I 1 ̅ space group. The other compositions were all found to crystallise in the monoclinic space group P 2 1 / n although Sr 1.5 Ca 0.5 CrSbO 6 was found to be phase separated into a calcium-deficient and calcium-rich phase, both having the space group P 2 1 / n . Sr 2 CrSbO 6 was found to order antiferromagnetically at 12 K and the ordered Cr 3+ moment was refined to be 2.39(1) µ B. The antiferromagnetic order was rapidly quenched on doping with Ca and compositions with x  ≥ 0.75 exhibited ferromagnetic order. T C increased with x to reach a maximum of 14 K at x  = 2.0, with an ordered moment of 2.56(3) µ B per Cr 3+ cation. The tilt angles of the B-site octahedra about [110] and [001] increase from 5.4(1)° and 4.6(1)° to 13.7(1)° and 13.9(1)°, respectively, across the series; the switch from antiferromagnetism to ferromagnetism occurs when both tilts are at a value of ~ 8°. [ABSTRACT FROM AUTHOR]

The temperature dependence of the crystal structure and thermoelastic properties of RbCaF 3 perovskite are reported from a high-resolution neutron powder diffraction investigation in the temperature interval 2–300 K. Two phase transitions have been identified from these data, the first from space group P m 3 ¯ m to I 4/ mcm , at 200 K, has been well characterized in earlier studies, the second, from space group to I 4/ mcm to Pbnm has previously been less well understood. New results from the former transition show the order parameter evolves with a critical exponent of 0.284(5), and the phase is characterized by an Einstein temperature of 192(8) K, and a Debye temperature of 270(10) K. The temperature variation of the tetragonal spontaneous strain in this phase is consistent with an additional fourth order invariant in the Landau potential. The second phase transition is found to be strongly first order and a temperature dependent, and heating rate/cooling rate dependent phase coexistence is found at all temperatures below ~ 80 K on heating, and ~ 65 K on cooling. The evolution of the orthorhombic unit cell is atypical in the region of the phase transition, with a and b exhibiting strong negative linear thermal expansion, whilst the c axis behaves in the expected manner. The crystal structure of the Pbnm phase at 2 K is reported from an unconstrained Rietveld refinement for the first time. [ABSTRACT FROM AUTHOR]

Polycrystalline Nd 2 MgRuO 6 has monoclinic P2 1 /n structure with an ordered arrangement of Mg 2+ and Ru 4+ ions. Magnetic ordering is observed at 1.5 K where the Ru sublattice exhibits type-I antiferromagnetic order with the magnetic moments parallel to the c -axis. The Nd 3+ cations show a ferromagnetic arrangement at this temperature. Nd 2 MgRuO 6 exhibits semiconductor like behaviour. Impedance analysis shows the contribution of grain alone to the conduction process till 231 K, above which both the grain and grain boundary contribute. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of La 3 Ni 2 NbO 9 and La 3 Ni 2 TaO 9 have been characterised by X-ray and neutron diffraction, electron microscopy, magnetometry and muon spin relaxation (µSR); the latter technique was also applied to La 3 Ni 2 SbO 9 . On the length scale of a neutron diffraction experiment, the six-coordinate sites of the monoclinic perovskite structure are occupied in a 1:1 ordered manner by Ni and a random ⅓Ni/⅔ B′ mixture. Electron microscopy demonstrated that this 1:1 ordering is maintained over microscopic distances, although diffuse scattering indicative of short-range ordering on the mixed site was observed. No magnetic Bragg scattering was observed in neutron diffraction patterns collected from La 3 Ni 2 B′ O 9 ( B′ = Nb or Ta) at 5 K although in each case µSR identified the presence of static spins below 30 K. Magnetometry showed that La 3 Ni 2 NbO 9 behaves as a spin glass below 29 K but significant short-range interactions are present in La 3 Ni 2 TaO 9 below 85 K. The contrasting properties of these compounds are discussed in terms of their microstructure. [ABSTRACT FROM AUTHOR]

RE (Co 0.667 Ga 0.333 ) 2 ( RE = Ho, Er) were characterized by neutron powder diffraction (NPD). Rietveld refinement of the NPD data at 280 K confirms the hexagonal MgZn 2 -type structure ( P 6 3 /mmc ), in accordance with the previous XRD results. Co/Ga occupancies on the 2 a and 6 h sites were refined to be 0.46/0.54(2) and 0.74/0.26(2), respectively, indicating a preference of Ga for the 2 a site and of Co for the 6 h site. Both materials are ferromagnetic, k = (000), with measureable moments only on the RE sites. The magnetic (Shubnikov) space group is P 6 3 / mm′c′ for the Er phase. Co moments refined to values of 0.1–0.3 μ B and are effectively zero within 3σ. The Er moment, 6.07(8) μ B at 3.5 K is parallel to the c axis and this orientation persists up to T C = 18.5 K, while the Ho moment has components along both the a and c axes with a total moment of 6.3(1) μ B at 3.5 K. Both moments are much reduced from the free ion values, 9 μ B (Er) and 10 μ B (Ho), which is attributed to crystal field effects. In addition, the Ho moment angle with the c axis is strongly temperature dependent, being roughly constant, ~ 24(6)° from T = 29 K to ~25 K, then increasing with decreasing temperature to 44(1)° at 3.5 K. Magnetic small angle neutron scattering (MSANS) was observed over a Q -range from 0.14 Å −1 to 0.50 Å −1 in both samples. The integrated MSANS of the Er phase peaks near T C , then decreases monotonically with decreasing temperature, behavior typical for a simple ferromagnet. On the other hand, the integrated MSANS for the Ho phase exhibits a weak peak around T C = 31 K, followed by a plateau to 25 K and a strong increase with decreasing temperatures, which tracks the evolution of the Ho moment angle with the c axis. [ABSTRACT FROM AUTHOR]

Lithium aluminum sulfide (Li 5 AlS 4 ) was synthesized by solid state reaction, and its crystal structure was characterized by ab initio structure determination on the basis of powder neutron diffraction (ND) data. Li 5 AlS 4 was found to have monoclinic unit cell (space group, P 2 1 / m ) with the lattice parameters: a = 6.8583(4) Å, b = 7.8369(4) Å, c = 6.2488(4) Å, and β = 90.333(4)°. This structure is built from a hexagonal close-packed ( hcp ) arrangement of sulfur atoms with a stacking sequence of …ABAB…. The hcp sulfide lattice consists of two different double-sulfide layers alternately stacked along the c -axis. Between the first pair of sulfur layers all the tetrahedral interstices (T + and T - sites) are filled with lithium and aluminum atoms. All octahedral interstices between the second pair of sulfur layers are occupied by the remaining lithium atoms. The structure of Li 5 AlS 4 is compared with those of various lithium-containing metal sulfides like Li 2 FeS 2 , NaLiMS 2 (M = Zn, Cd), Li 4 GeS 4 , LiM′S 2 (M′ = Al, Ga, In) and γ-Li 3 PS 4 . Each sulfide represents a specific distribution of lithium atoms in the lattice depending on how the octahedral and tetrahedral interstitial sites are filled. The low ionic conductivity of Li 5 AlS 4 (9.7 × 10 −9 S cm −1 at 323 K) relative to other sulfides may be due to the highly-ordered distribution of the lithium atoms in the layered structure and the lack of adjacent void spaces that can be used for lithium ion hopping. [ABSTRACT FROM AUTHOR]

Solid solution of sodium niobate and sodium bismuth titanate [(1-x)NaNbO 3 -x(Na 0.5 Bi 0.5)TiO 3 : xNBT)] is an important lead-free eco-friendly piezo-ceramic material. In the present work, we report an investigation of the phase stabilities of this solid solution using powder x-ray and neutron diffraction techniques for the entire range of composition. We observed the disappearance of certain peaks and changes in the main perovskite peaks in the powder diffraction data suggesting structural phase transitions with composition. Rietveld analysis of combined x-ray and neutron powder diffraction data is performed to obtain single correct structural model wherever possible. Detailed analyses of powder diffraction data for composition range 0.0 ≤ x ​< ​0.15 revealed the coexistence of orthorhombic ( P bma) and ( P mc2 1) phases and an orthorhombic phase with space group P bnm and cell dimensions √2a p ​× ​√2 b p ​× ​6 c p gets stabilized for 0.15 ≤ x ​< ​0.20. On further increasing NBT content in NaNbO 3 matrix (0.20 ≤ x ​< ​0.60), a mixed orthorhombic ( P bnm) phase and tetragonal ( P 4bm) phase is confirmed by Rietveld refinement. Further, in the composition range 0.60 ≤ x ​≤ ​0.80, the tetragonal ( P 4bm) phase coexists with the ferroelectric rhombohedral ( R 3c) phase and finally for composition x ​> ​0.80, it completely transforms to rhombohedral ( R 3c) phase. The presence of phase coexistence in various composition ranges indicates the first order nature of these phase transitions. A detailed structural phase diagram of the system is presented at ambient conditions. We compositionally designed (1-x) NaNbO 3 - x(Na 0.5 0Bi 0.50)TiO 3 solid solutions and investigated their phase stabilities using combined powder x-ray and neutron diffraction technique. Detailed analyses of powder diffraction data for composition range 0.0 ≤ x ​< ​0.15 revealed the coexistence of orthorhombic ( P bma) and ( P mc2 1) phases whereas an orthorhombic phase with space group P bnm and cell dimensions √2a p ​× ​√2 b p ​× ​6 c p gets stabilized for 0.15 ≤ x ​< ​0.20. On further increasing NBT content in NaNbO 3 matrix (0.20 < x ​< ​0.60), a mixture of orthorhombic ( P bnm) phase and tetragonal ( P 4bm) phase is found by Rietveld refinement. Further, in the composition range 0.60≤ x ​≤ ​0.80, the tetragonal ( P 4bm) phase coexists with the ferroelectric rhombohedral ( R 3c) phase and finally for composition x ​> ​0.80, it completely transforms to rhombohedral ( R 3c) phase. The presence of phase coexistence in various composition ranges indicates the first order nature of these phase transitions. A detailed structural phase diagram of the system is presented at ambient conditions. [Display omitted] • We compositionally designed (1-x) NaNbO 3 - x(Na 0.5 Bi 0.5) TiO 3 solid solutions and investigated their phase stabilities using combined powder x-ray and neutron diffraction technique. • We observed the disappearance of certain peaks and changes in the main perovskite peaks in the powder diffraction data suggesting structural phase transitions with composition. • Rietveld analysis of combined x-ray and neutron powder diffraction data is performed to obtain single correct structural model wherever possible. • Detailed analyses of powder diffraction data suggest phase stabilities and phase-coexistences in various composition ranges. [ABSTRACT FROM AUTHOR]

Crystal structures of the high-pressure synthesized perovskite phases of the (1- x)BiFe 0.5 Sc 0.5 O 3 - x LaFe 0.5 Sc 0.5 O 3 (0 ​= ​ x ​≤ ​1) system and their temperature and pressure behaviours were studied using laboratory and synchrotron X-ray diffractions as well as neutron diffraction. At room temperature, the as-prepared phases with x ​≤ ​0.05 have an antipolar structure with the Pnma symmetry and with the √2 a p ​× ​4 a p ​× ​2√2 a p superstructure (where a p is the pseudocubic perovskite unit-cell parameter). An incommensurately modulated phase with the Imma (00γ) s 00 superspace group is observed for 0.10 ​= ​ x ​≤ ​0.33, while a non-polar Pnma phase (√2 a p ​× ​2 a p ​× ​√2 a p) is stable when x ​≥ ​0.34. The antipolar Pnma phase in the as-prepared samples with composition corresponding to x ​= ​0 transforms into the polar Ima 2 one via irreversible annealing-caused transformation accompanied by a formation of a high-temperature intermediate polar R 3 c polymorph, while the antipolar Pnma phase in samples with x ​= ​0.05 is stable until the decomposition temperature. In the solid solutions with 0.10 ​= ​ x ​≤ ​0.33, increasing temperature was found to result in a reversible transformation of the Imma (00 γ)s00 phase into a non-polar Pnma one. The transition temperature decreases with increasing x. A hydrostatic pressure of few GPa was also shown to induce a reversibl e Imma (00 γ)s00 → Pnma transformation. The normalized unit-cell volume and the primitive perovskite cell parameters of the BL x FSO phases as a function of the lanthanum content (x) with the tentative borders of the phase ranges. The space groups and the superstructures are indicated (a p is the pseudocubic primitive perovskite unit-cell parameter). [Display omitted] • SynThesis of bulk Bi 1- x La x Fe 0.5 Sc 0.5 O 3 phases with x ​< ​0.80 requires high pressure. • No compositional ranges of phase coexistence in the as-synthesized solid solutions. • Compositional behaviour of the normalized unit-cell volume is strongly non-linear. • Annealing of the x ​= ​0 composition induces irreversible Pnma.→ R 3 c → Ima 2 crossover • Increasing temperature or pressure lead to reversible Imma (00 γ)s00.→ Pnma transition [ABSTRACT FROM AUTHOR]

Polycrystalline samples of Ln MnFeGe 4 O 12 ( Ln = Y, Eu, Lu) have been prepared using the ceramic method and characterised by a combination of magnetometry, Mössbauer spectroscopy, X-ray diffraction and neutron diffraction. They all adopt the space group P 4/ nbm with a ~ 9.670, c ~ 4.81 Å and show long-range antiferromagnetic order with transition temperatures 15 ≤ T N /K ≤ 17. The magnetic structure is the same in each case and consists of an A-type ordering of (001) planes; the ordered spins lie in the (001) plane. Comparison with isostructural compounds leads to the conclusion that subtle structural changes play a greater role than the electronic configuration of the cation in determining the magnetic structure. [ABSTRACT FROM AUTHOR]

A fluoride-ion conductor, γ -PbSnF 4 , was synthesized by the mechanical milling. In addition, β -PbSnF 4 was obtained by aging the γ -PbSnF 4 at 473 K. The electrical conductivity of β -PbSnF 4 is relatively higher than that of γ -PbSnF 4 at 298 K. The crystal structure analysis of γ - and β -PbSnF 4 was carried out using neutron diffraction data. From the obtained occupancies, fluoride ions were located at the F γ (1) normal site (62%) and F γ (2) interstitial site (38%) in γ -PbSnF 4 and the F β (1) normal site (31%), F β (2) normal site (25%), and F β (3) interstitial site (44%) in β -PbSnF 4 . In particular, the number of fluoride ions at the F interstitial site increased after the γ -to- β phase transition: 38% at F γ (2) to 44% at F β (3). It is most likely that the ratio of fluoride ions to vacancies (or the effective carrier concentration) was optimized in the “–F β (1)–F β (3)–F β (3)–F β (1)–” conduction pathways of fluoride ions in β -PbSnF 4 . [ABSTRACT FROM AUTHOR]

The structure of α -Cs 2 Mo 2 O 7 (monoclinic in space group P 2 1 / c ), which can form during irradiation in fast breeder reactors in the space between nuclear fuel and cladding, has been refined in this work at room temperature from neutron diffraction data. Furthermore, the compounds' thermal expansion and polymorphism have been investigated using high temperature X-ray diffraction combined with high temperature Raman spectroscopy. A phase transition has been observed at T tr ( α → β )=(621.9±0.8) K using Differential Scanning Calorimetry, and the structure of the β -Cs 2 Mo 2 O 7 phase, orthorhombic in space group Pbcm , has been solved ab initio from the high temperature X-ray diffraction data. Furthermore, the low temperature heat capacity of α -Cs 2 Mo 2 O 7 has been measured in the temperature range T =(1.9–313.2) K using a Quantum Design PPMS (Physical Property Measurement System) calorimeter. The heat capacity and entropy values at T =298.15 K have been derived as C p , m o ( Cs 2 Mo 2 O 7 , cr , 298.15 K ) = ( 211.9 ± 2.1 ) J K − 1 mol − 1 and S m o ( Cs 2 Mo 2 O 7 , cr , 298.15 K ) = ( 317.4 ± 4.3 ) J K − 1 mol − 1 . When combined with the enthalpy of formation reported in the literature, these data yield standard entropy and Gibbs energy of formation as Δ f S m o ( Cs 2 Mo 2 O 7 , cr , 298.15 K ) = − ( 628.2 ± 4.4 ) J K − 1 mol − 1 and Δ f G m o ( Cs 2 Mo 2 O 7 , cr , 298.15 K ) = − ( 2115.1 ± 2.5 ) kJ mol − 1 . Finally, the cesium partial pressure expected in the gap between fuel and cladding following the disproportionation reaction 2Cs 2 MoO 4 =Cs 2 Mo 2 O 7 +2Cs(g)+ 1/2 O 2 (g) has been calculated from the newly determined thermodynamic functions. [ABSTRACT FROM AUTHOR]

The crystal structure of new W 3 CoB 3 -type {Y, Gd - Ho} 3 Co 3.25 Al 0.75 , Gd 3 Co 3.5 Al 0.5 and Tb 3 Co 3 Al compounds ( Cmcm . N 63, oC 28) has been established using powder X-ray diffraction studies. The magnetic properties of Gd 3 Co 3.5 Al 0.5 , Gd 3 Co 3.25 Al 0.75 and Tb 3 Co 3.25 Al 0.75 were determined by bulk magnetization measurements and neutron diffraction studies. Gd 3 Co 0.5 Al 0.5 , Gd 3 Co 3.25 Al 0.75 and Tb 3 Co 3.25 Al 0.75 exhibit ferrimagnetic ordering below 196 K, 161 K and 151 K, respectively. Tb 3 Co 3.25 Al 0.75 shows a spin-reorientation transition at ~42 K. Below the ferrimagnetic ordering temperature Gd 3 Co 3.25 Al 0.75 and Tb 3 Co 3.25 Al 0.75 are soft ferrimagnets, meanwhile Tb 3 Co 3.25 Al 0.75 shows magnetic hardness below the spin-reorientation transition with remanent magnetization per formula unit of 9.7 μ B and coercive field of 15 kOe at 2 K. The magnetocaloric effects of Gd 3 Co 3.25 Al 0.75 and Tb 3 Co 3.25 Al 0.75 were calculated in terms of isothermal magnetic entropy change and they reach maximum values of −4.9 J/kg·K at 135–145 K and −3.7 J/kg·K at 115–135 K, respectively, for a field change of 0–50 kOe. Low temperature magnetic ordering in Tb 3 Co 3.25 Al 0.75 is accompanied by a positive magnetocaloric effect with isothermal magnetic entropy changes of +13.6 J/kg·K at 10 K for a field change of 0–50 kOe and +0.9 J/kg K at 45 K for a field change of 0–10 kOe. Neutron diffraction study in zero applied field shows mixed ferro-antiferromagnetic ordering of Tb 3 Co 3.25 Al 0.75 with a wave vector K 0 =[0, 0, 0]. Below ~ 137 K Tb 3 Co 3.25 Al 0.75 exhibits non-collinear ferrimagnetic ordering of terbium and cobalt sublattices with resulting of b -axis ferromagnetic and c -axis antiferromagnetic components of Cmc′m ={ 1 , m x }×{ 1 , m z /[0, 0, 1/2]}×{ 1 , i′ }×{ 1 , 1 /[1/2, 1/2, 0]} magnetic space group. The spin-reorientation transition in Tb 3 Co 3.25 Al 0.75 below ~38 K corresponds to appearance of additional a -axis ferromagnetic component and decreasing of symmetry of magnetic ordering down to C2′/c ={ 1 , m z /[0, 0, 1/2]}×{ 1 , i′ }×{ 1 , 1 /[1/2, 1/2, 0]} magnetic space group. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of Ca Ln 2 Ni 2 WO 9 ( Ln =La, Pr, Nd) have been synthesized and characterised by a combination of X-ray and neutron diffraction, electron microscopy and magnetometry. Each composition adopts a perovskite-like structure with a ~5.50, b ~5.56, c ~7.78 Å, β ~90.1° in space group P 2 1 / n . Of the two crystallographically distinct six-coordinate sites, one is occupied entirely ( Ln =Pr) or predominantly ( Ln =La, Nd) by Ni 2+ and the other by Ni 2+ and W 6+ in a ratio of approximately 1:2. None of the compounds shows long-range magnetic order at 5 K. The magnetometry data show that the magnetic moments of the Ni 2+ cations form a spin glass below ~30 K in each case. The Pr 3+ moments in CaPr 2 Ni 2 WO 9 also freeze but the Nd 3+ moments in CaNd 2 Ni 2 WO 9 do not. This behaviour is contrasted with that observed in other ( A , A ') B 2 B 'O 9 perovskites. [ABSTRACT FROM AUTHOR]

Electron and hole doping in Co 3 Sn 2 S 2 , through chemical substitution of cobalt by the neighbouring elements, nickel and iron, affects both the structure and thermoelectric properties. Electron doping to form Co 3−x Ni x Sn 2 S 2 (0≤x≤3) results in an expansion of the kagome layer and materials become increasingly metallic as cobalt is substituted. Conversely, hole doping in Co 3−x Fe x Sn 2 S 2 (0≤x≤0.6) leads to a transition from metallic to n -type semiconducting behaviour at x=0.5. Iron substitution induces a small increase in the separation between the kagome layers and improves the thermoelectric performance. Neutron diffraction data reveal that substitution occurs at the Co 9( d ) site in a disordered fashion. Mössbauer spectroscopy reveals two iron environments with very different isomer shifts, which may be indicative of a mixed-valence state, while Sn exhibits an oxidation state close to zero in both series. Co 2.6 Fe 0.4 Sn 2 S 2 exhibits a maximum figure-of-merit, ZT=0.2 at 523 K while Co 2.4 Fe 0.6 Sn 2 S 2 reaches a power factor of 10.3 μW cm −1 K −2 close to room temperature. [ABSTRACT FROM AUTHOR]

The impact of chemical doping of the type Sr 2−x A x YRuO 6 ( A =Ca, Ba) on the low temperature magnetic properties of Sr 2 YRuO 6 , probed using variable temperature magnetic susceptibility, neutron diffraction and heat capacity measurements, are described. Specific-heat measurements of un-doped Sr 2 YRuO 6 reveal two features at ∼26 and ∼30 K. Neutron scattering measurements at these temperatures are consistent with a change from a 2D ordered state to the 3D type 1 AFM state. Magnetic and structural studies of a number of doped oxides are described that highlight the unique low temperature behavior of Sr 2 YRuO 6 and demonstrate that doping destabilizes the intermediate 2D ordered state. [ABSTRACT FROM AUTHOR]

A polycrystalline sample of LaSr 2 Cr 2 SbO 9 has been synthesised using a standard ceramic method and characterized by x-ray and neutron diffraction, magnetometry and electron microscopy. The perovskite-related compound crystallises in the triclinic space group I 1 ̅ with unit cell parameters of a =5.5344(6) Å, b =5.5562(5) Å, c =7.8292(7) Å, α=89.986(12)°, β =90.350(5)° and γ=89.926(9)° at room temperature. The two crystallographically-distinct, six-coordinate cation sites are occupied by Cr 3+ and Sb 5+ in ratios of 0.868(2):0.132(2) and 0.462(2):0.538(2). Ac and dc magnetometry revealed that LaSr 2 Cr 2 SbO 9 is ferrimagnetic below 150 K with a magnetisation of ~1.25 µ B per formula unit in 50 kOe at 5 K. Neutron diffraction showed that the cations on the two sites order in a G-type arrangement with a mean Cr 3+ moment of 2.17(1) µ B at 5 K, consistent with a magnetisation of 1.32 µ B per formula unit. [ABSTRACT FROM AUTHOR]

Magnetic structure of CaFe 5 O 7 ferrite has been studied jointly from neutron powder diffraction data and spectroscopic Mössbauer measurements in the thermal range from 5 to 500 K. This coupled work highlights three distinct magnetic domains around two specific temperatures: T M =125 K and T N =360 K. The latter corroborates the structural monoclinic-orthorhombic transition previously reported by transmission electron microscopy techniques and X-ray thermodiffractometry. Complementary heat capacity measurements have confirmed this first order transition with a sharp peak at 360 K. Interestingly, this large study has revealed a second magnetic transition associated to a spin rotation at 125 K similar to this one reported by Morin in α-Fe 2 O 3 hematite at T M =260 K. [ABSTRACT FROM AUTHOR]

Pulsed neutron diffraction and synchrotron X-ray diffraction measurements were performed on Se 100- x Te x bulk glasses with x =10, 20, 30 and 40. The coordination numbers obtained from the diffraction results demonstrate that Se and Te atoms are twofold coordinated and the glass structure is formed by the chain network. The three-dimensional structure model for Se 60 Te 40 glass obtained by using reverse Monte Carlo modelling shows that the alternating arrangements of Se and Te atoms compose the major part of the chain clusters but several other fragments such as Se n chains and Te-Te dimers are also present in large numbers. The chain clusters have geometrically disordered forms and the interchain atomic order is different from those in the crystal structures of trigonal Se and trigonal Te. [ABSTRACT FROM AUTHOR]