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Single crystals (SCs) of the compounds Eu3Ag2In9 and EuCu2Ge2 were synthesized through the reactions run in liquid indium. Eu3Ag2In9 crystallizes in the La3Al11 structure type [orthorhombic space group (SG) Immm] with the lattice parameters: a = 4.8370(1) A, b = 10.6078(3) A, and c = 13.9195(4) A. EuCu2Ge2 crystallizes in the tetragonal ThCr2Si2 structure type (SG I4/mmm) with the lattice parameters: a = b = 4.2218(1) A, and c = 10.3394(5) A. The crystal structure of Eu3Ag2In9 is comprised of edge-shared hexagonal rings consisting of indium. The one-dimensional chains of In6 rings are shared through the edges, which are further interconnected with other six-membered rings forming a three-dimensional (3D) stable crystal structure along the bc plane. The crystal structure of EuCu2Ge2 can be explained as the complex [CuGe](2+δ)– polyanionic network embedded with Eu ions. These polyanionic networks present in the crystal structure of EuCu2Ge2 are shared through the edges of the 011 plane containing Cu and Ge ...

The title compound is prepared by repeated calcination of stoichiometric amounts of Dy2O3 and WO3 (1100 °C, 10 h) followed by quenching or slow cooling to 25 °C.

Li 4 MgOsO 6 was synthesized by two different solid-state reaction procedures. The crystal structures were determined by X-ray powder diffraction technique and it was revealed that Li 4 MgOsO 6 crystallizes in two different crystal symmetries in ordered rock salt structure type, namely monoclinic C2/m and orthorhombic Fddd . The unit cell constants for the monoclinic system are a =5.1074(4) A, b= 8.8182(4) A, c= 5.0902(2) A, and β =109.845 ( 4)° and those of the orthorhombic structure are a =5.8485(1) A, b =8.3821(1) A, and c =17.6212(3) A. In both systems, Os 6+ ions reside exclusively in a specific crystallographic position while Li + and Mg 2+ ions exhibit mix occupancy. The temperature dependent magnetic susceptibility data for both S=1 osmate systems do not support the occurrence of any magnetic transition down to 2 K. The Curie–Weiss fit to the paramagnetic regime of the magnetic susceptibility data reveal highly negative θ value (−114.81 K and −121.87 K for C2/m and for Fddd systems , respectively ) , which are indicative of predominant antiferromagnetic (AFM) interactions in both systems. The experimental effective magnetic moment ( μ eff ) value for the monoclinic phase is 2.13 μB and that of the orthorhombic system is 2.34 μB . Due to the rather strong AFM interactions and lack of magnetic transition down to 2 K, both of these novel osmates are placed in the class of highly frustrated magnets. Low temperature magnetic susceptibility (below 2 K) and dynamic magnetic properties studies (μsr studies) are in order to better understand the magnetic ground states of these two polymorphs of Li 4 MgOsO 6 .

A new series of heterometallic 3d–4f sandwich type phosphotungstates, [Ln{PCo2W10O38(H2O)2}2]11– (Ln = SmIII, EuIII, GdIII, TbIII, DyIII, HoIII, ErIII, TmIII, YbIII, and LuIII, denoted 1a–10a, respectively), have been synthesized by a one-pot reaction procedure on reacting the dilacunary K14[P2W19O69(H2O)]·24H2O precursor with Ln(NO3)3·nH2O and Co(NO3)2·6H2O in an aqueous potassium chloride solution. All the compounds were isolated as potassium salts and further characterized with different analytical techniques such as single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, high-resolution electrospray ionization mass spectrometry, elemental analysis by inductively coupled plasma atomic emission spectroscopy, magnetic measurement, and thermogravimetric analysis. Single-crystal X-ray diffraction analysis of the compounds reveals that all these compounds are isostructural and crystallized in the orthorhombic crystal system in space group Iba2. The polyanions contain the α-1,5 isomer of d...

We describe the synthesis, crystal structures, and optical absorption spectra/colours of 3d transition-metal-substituted lyonsite-type oxides Li3Al1-xMxIII(MoO4)(3) (0

The crystal structure, magnetic properties and magnetocaloric effect (MCE) of GdCoC2 have been studied. The compound crystallizes in an orthorhombic CeNiC2-type structure which belongs to the Amm2 space group. A giant reversible MCE is observed in GdCoC2 accompanied by a second-order paramagnetic to ferromagnetic (PM–FM) phase transition around the Curie temperature ∼15 K. For the magnetic field change of 0–5 T, the maximum values of the magnetic entropy change (−ΔSmaxM), relative cooling power (RCP), and refrigerant capacity (RC) are 28.4 J kg−1 K−1, 566 J kg−1 and 369 J kg−1, respectively. The present results indicate that GdCoC2 is a promising candidate for low temperature magnetic refrigeration.

The intermetallic compound EuAu3Al2 has been prepared by reaction of the elements in tantalum ampules. The structure was refined from single-crystal data, indicating that the title compound crystallizes in the orthorhombic crystal system (a = 1310.36(4), b = 547.87(1), c = 681.26(2) pm) with space group Pnma (wR2 = 0.0266, 1038 F(2) values, 35 parameters) and is isostructural to SrAu3Al2 (LT-SrZn5 type). Full ordering of the gold and aluminum atoms was observed. Theoretical calculations confirm that the title compound can be described as a polar intermetallic phase containing a polyanionic [Au3Al2](δ-) network featuring interconnected strands of edge-sharing [AlAu4] tetrahedra. Magnetic measurements and (151)Eu Mossbauer spectroscopic investigations confirmed the divalent character of the europium atoms. Ferromagnetic ordering below TC = 16.5(1) K was observed. Heat capacity measurements showed a λ-type anomaly at T = 15.7(1) K, in line with the ordering temperature from the susceptibility measurements. The magnetocaloric properties of EuAu3Al2 were determined, and a magnetic entropy of ΔSM = -4.8 J kg(-1) K(-1) for a field change of 0 to 50 kOe was determined. Band structure calculations found that the f-bands of Eu present at the Fermi level of non-spin-polarized calculations are responsible for the ferromagnetic ordering in this phase, whereas COHP chemical bonding coupled with Bader charge analysis confirmed the description of the structure as covalently bonded polyanionic [Au3Al2](δ-) network interacting ionically with Eu(δ+).

Two new ternary copper-containing arsenides, Sr2Cu3As3 and Eu2Cu3As3, were synthesized through Pb-flux reactions. In combination with theoretical calculations, the crystal structures of these compounds were determined through single-crystal X-ray diffraction. Both compounds crystallize in the orthorhombic space group Cmcm (no.63) with the cell parameters a = 4.2465(6)/4.1866(5) A, b = 17.604(3)/17.486(2) A, and c = 4.2552(6)/4.2096(5) A for the Sr- and Eu-containing compounds, respectively. Temperature-dependent magnetic susceptibility measurements suggest that both ferromagnetic and antiferromagnetic coupling exists in the structure of Eu2Cu3As3 for the Eu 4f states. According to DFT calculations, these compounds are metallic, and the Cu 3d orbitals make significant contributions to the states around the Fermi level.

The new ternary transition metal-rich borides Ta2OsB2 and TaRuB have been successfully synthesized by arc-melting the elements in a water-cooled crucible under an argon atmosphere. The crystal structures of both compounds were solved by single-crystal X-ray diffraction and their metal compositions were confirmed by EDX analysis. It was found that Ta2OsB2 and TaRuB crystallize in the tetragonal Nb2OsB2 (space group P4/mnc, no. 128) and the orthorhombic NbRuB (space group Pmma, no. 51) structure types with lattice parameters a=5.878(2) A, c=6.857(2) A and a=10.806(2) A, b=3.196(1) A, c=6.312(2) A, respectively. Furthermore, crystallographic, electronic and bonding characteristics have been studied by density functional theory (DFT). Electronic structure relaxation has confirmed the crystallographic parameters while COHP bonding analysis indicates that B2-dummbells are the strongest bonds in both compounds. Moreover, the formation of osmium dumbbells in Ta2OsB2 through a Peierls distortion along the c-axis, is found to be the origin of superstructure formation. Magnetic susceptibility measurements reveal that the two phases are Pauli paramagnets, thus confirming the theoretical DOS prediction of metallic character. Also hints of superconductivity are found in the two phases, however lack of single phase samples has prevented confirmation. Furthermore, the thermodynamic stability of the two modifications of AMB (A=Nb, Ta; M =Ru, Os) are studied using DFT, as new possible phases containing either B4- or B2-units are predicted, the former being the most thermodynamically stable modification.

Substitution of aliovalent N3– and F– anions in place of O2– in ZnO brings about major changes in the electronic structure and properties, the composition, even with 10 atomic percent or less of the two anions, rendering the material yellow colored with a much smaller band gap. We have examined the variation of band gap of ZnO with progressive substitution of N and F and more importantly prepared Zn2NF which is the composition one obtains ultimately upon complete replacement of O2– ions. In this article, we present the results of a first complete study of the crystal and electronic structures as well as of properties of a stable metal nitride fluoride, Zn2NF. This material occurs in two crystal forms, tetragonal and orthorhombic, both with a band gap much smaller than that of ZnO. Electronic structures of Zn2NF as well as ZnO0.2N0.5F0.3 investigated by first-principles calculations show that the valence bands of these are dominated by the N (2p) states lying at the top. Interestingly, the latter is a p-ty...

An efficient and eco-friendly procedure has been developed for the synthesis of various 2,2’-arylmethylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) derivatives which were isolated and characterized by melting point, IR, 1H-NMR, 13C-NMR and mass spectrometric techniques. Out of the fourteen compounds synthesized, four compounds yielded crystals suitable for single crystal X-ray analysis which showed that 2,2’-phenylmethylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) crystallizes in the tetragonal system with space group I 4 1 /a, 2,2’-(3-nitrophenyl)methylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) crystallizes in the monoclinic system with space group P 2 1 /n, 2,2’-(4-nitrophenyl)methylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) crystallizes in the orthorhombic system with space group Pca21 and 2,2’-(4-chlorophenyl)methylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) crystallizes in the monoclinic space group P21/c.

The exploitable properties of many materials are intimately linked to symmetry-lowering structural phase transitions. We present an automated and exhaustive symmetry-mode method for systematically exploring and solving such structures which will be widely applicable to a range of functional materials. We exemplify the method with an investigation of the Bi2Sn2O7 pyrochlore, which has been shown to undergo transitions from a parent γ cubic phase to β and α structures on cooling. The results include the first reliable structural model for β-Bi2Sn2O7 (orthorhombic Aba2, a = 7.571833(8), b = 21.41262(2), and c = 15.132459(14) A) and a much simpler description of α-Bi2Sn2O7 (monoclinic Cc, a = 13.15493(6), b = 7.54118(4), and c = 15.07672(7) A, β = 125.0120(3)°) than has been presented previously. We use the symmetry-mode basis to describe the phase transition in terms of coupled rotations of the Bi2O′ anti-cristobalite framework, which allow Bi atoms to adopt low-symmetry coordination environments favored by ...

(Eu3+, Bi3+)-codoped CaZrO3 phosphor crystallizing in the orthorhombic structure was synthesized from a mixture of CaCO3, ZrO2, Eu2O3, and Bi2O3 using the solid-state reaction method. The structural and optical properties of this phosphor were investigated using X-ray diffraction analysis, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and PL decay measurements. The effects of Bi3+ codoping on the Eu3+ emission properties were discussed in detail. Temperature dependence of the PL intensity was also measured between T = 20 and 450 K and obtained a quenching energy of Eq ∼ 0.1 eV. Remarkably, the red emission intensity of Eu3+ in the (Eu3+, Bi3+)-codoped phosphor was enhanced more than 10 times compared to the Eu3+ singly doped phosphor, thereby suggesting an efficient resonant energy transfer from Bi3+ to Eu3+. The asymmetry ratio (5D0 → 7F2)/(5D0 → 7F1) for the Eu3+ emission had different values with different Eu3+ concentrations, indicating that its local site depends on the Eu3+/Bi3+ concentration. Comparative discussion was also given on the PL spectra for some red-emitting phosphors, CaZrO3:Eu3+, Bi3+, SnO2:Eu3+, and K2SiF6:Mn4+.

In this review are classified and analyzed structural parameters of over one hundred and thirty monomeric organoplatinum complexes with trans - PtP 2 CCl inner coordination sphere. These complexes crystallized in four crystal systems: tetragonal (×2), orthorhombic (×22), triclinic (×41) and monoclinic (×69). These complexes from the coordination mode of the respective donor ligands, which build up inner coordination sphere, trans - PtP 2 CCl, can be divided into the five groups. There is variety of donor ligands, monodentate PL,CL and Cl; homobidentate- P,P’; heterobidentate- P/C and P/Cl, and even heterotridentate- P,C,P donor ligands. The chelating ligands created variety of metallocyclic rings. There are several examples which exist in two isomeric forms and some other examples which contain two crystallographically independent molecules within the same crystal. These isomeric forms as well as independent molecules are example of distortion isomerism. The comprehensive mean Pt-L bond distances elongated in the order: 2.01 A (C, trans to Cl)

Orthovanadates LiCdVO4 and Li0.75Na0.25CdVO4 compounds have been obtained by the conventional solid-state reaction and characterized by X-ray powder diffraction. The crystal structure determination, of both samples, indicates that they are isostructural. The following crystal data were obtained: orthorhombic, Cmcm, Z = 4, (a = 5.924(1) A, b = 8.980 (2) A, c = 6.504(1) A and V = 346.064(1) A3) for LiCdVO4 and (a = 5.899(1) A, b = 9.039(2) A, c = 6.629(1) A and V = 352.878(1) A3) for Li0.75Na0.25CdVO4. Impedance spectroscopy measurements of LiCdVO4 and Li0.75Na0.25CdVO4 were conducted in the frequency and temperature range (209 Hz–1 MHz) and (582 K–709 K), respectively. Besides, the impedance spectra are well fitted to an equivalent circuit consisting of series combination of grains and grains boundaries. It was found that the non-overlapping small polaron tunneling (NSPT) model is suitable to describe the conduction mechanism in these two compounds.

A novel material of HfScMo2VO12 with negative thermal expansion (NTE) and intense white-light emission is presented. Structural analysis shows that it adopts an orthorhombic structure with the space group Pbcn and exhibits excellent NTE over a wide temperature range. The linear coefficient of thermal expansion was measured to be −2.78 × 10−6 K−1 (−150 to 675 K) and −2.99 × 10−6 K−1 (300–780 K) by dilatometers and αl = −2.11 × 10−6 K−1 from temperature-dependent X-ray diffraction. Besides the NTE property, HfScMo2VO12 possesses intense wide-band photoluminescence (PL) covering the visible region. The commission International de I'Eclairage (CIE) chromaticity coordinate is (0.27, 0.39) at room temperature and (0.33, 0.36) at 10 K, respectively. The integration of low NTE with intense white-light emission suggests potential applications of this material in white light emission diodes and other devices.

Two new congruent-melting alkali metal diphosphates, Rb2CdP2O7 and Cs2CdP2O7, were synthesized by conventional solid-state reactions. Single-crystal X-ray structural analyses showed that M2CdP2O7 (M = Rb, Cs) feature two-dimensional [CdP2O7](2-) layers that are composed of CdO5 pyramids and P2O7 dimers. The Rb+ and Cs+ cations ions fill the interlayers. The flexible P2O7 dimers could be bent and distorted if the Cs+ ion was substituted by the Rb+ ion, which led to crystallization of the Rb2CdP2O7 compound in the lower symmetry monoclinic space group P2(1)/c (No. 14) and crystallization of the Cs2CdP2O7 compound in the high-symmetry orthorhombic space group Pnma (No. 53). Thermal analyses showed that the two compounds melt congruently and that the melting point of Rb2CdP2O7 compound is lower than that of the Cs2CdP2O7 compound owing to distortion of the P2O7 dimers. IR spectroscopy and UV/Vis-near-IR diffuse reflectance spectroscopy were performed on the reported compounds.

Two new zincoborate fluorides with the common formula BaZn2B2O6·nBa2BO3F (n = 1, 2) have been successfully synthesized for the relationship study between the band gaps and crystal structures in zinc-containing borate fluorides. Ba3Zn2B3O9F with n = 1 in the common formula belongs to the orthorhombic space group Pnma (No. 20), and Ba5Zn2B4O12F2 with n = 2 in the common formula crystallizes in the monoclinic space group C2/c (No. 62). They can both be seen as compounds with the n[Ba2BO3F]∞ (n = 1 or 2) layer inserted in the structure of BaZn2B2O6. UV–vis–near-IR diffuse-reflectance spectra show that the band gaps of BaZn2B2O6·nBa2BO3F (n = 0, 1, 2) gradually increase with more [Ba2BO3F]∞ layers inserted. The first-principles calculation indicates that the inserted n[Ba2BO3F]∞ layers play a positive effect in increasing the band gaps of zincoborate fluorides. Furthermore, the IR spectra, thermal behaviors, and refractive indices of these compounds are also studied.

Sr 4−x Al 14 O 25 :xEu 3+ (x varies from 0.02 to 0.06) phosphors were prepared at high temperature via solid-state method. The crystal structure of Sr 4 Al 14 O 25 :Eu 3+ was determined to be orthorhombic crystal system with Pmmm space group. The excitation spectrum of Sr 3.96 Al 14 O 25 :0.04Eu 3+ shows four excitation bands at 308 nm, 360 nm, 383 nm, and 411 nm, respectively. The first excitation band, which is centered at 308 nm, is assigned to the charge-transfer (CTLM) band of Eu 3+ -O 2− , and others are assigned to intra-4f transitions between 393 nm and 450 nm. The emission spectrum of Sr 3.96 Al 14 O 25 :0.04Eu 3+ exhibits a series of emission bands which are attributed to the 5 D 0 - 7 F j (j = 0–4) transitions of Eu 3+ ions. The luminescence studies revealed that the Eu 3+ ions show high luminescence efficiency in emitting red light at 616 nm. The thermo-luminescence glow curve of Sr 3.96 Al 14 O 25 :0.04Eu 3+ shows three overlapped glow peaks between 100 °C and 400 °C which are related to the defects at different trap depths. One of the selected glow curves was analyzed by using glow curve deconvolution (GCD) method. In order to explore the related kinetic parameters of P1 Gartia, Singh & Mazumdar peak shape (PS) method was also used.

New fluorite-related quaternary rare earth oxides Pr 2 YRuO 7 and La 2 TbRuO 7 have been prepared. They crystallize in an orthorhombic superstructure of cubic fluorite with space group Cmcm . Through magnetic susceptibility and specific heat measurements, Pr 2 YRuO 7 shows an antiferromagnetic transition at 27 K, which is considerably lowered compared with that for Pr 3 RuO 7 . Analysis of the magnetic specific heat indicates that the magnetic behavior observed at 27 K for Pr 2 YRuO 7 is predominantly due to the magnetic interactions between Ru ions, and that the interactions between the Pr 3+ and Ru 5+ ions are also important. La 2 TbRuO 7 shows magnetic ordering at 9.0 K, which is ascribed to the magnetic ordering between Ru 5+ ions from the analysis of the magnetic specific heat data.

Perovskite oxide La0.3Sm0.2Sr0.5Ti0.5Fe0.5O3 has been synthesized by a citrate-gel precursor method. The Rietveld analysis of the XRD data showed that the sample crystallizes with a orthorhombic structure in the space group Pbnm. Magnetic properties suggest that antiferromagnetic interactions are dominant due to Fe3+–O–Fe3+ units.

The crystal structures of europium niobate, EuNbO3, have been examined over a wide temperature range between 20 and 500 K using synchrotron X-ray diffraction. We have observed two successive structural phase transitions at 360 and 460 K. Below 350 K, EuNbO3 adopts an orthorhombic perovskite structure (space group Imma), which is characterized by NbO6 octahedral tilting about the pseudocubic two-fold axis. The result differs from previous reports in which EuNbO3 was assigned to a cubic aristotype (space group Pm 3 ¯ m) of perovskite at room temperature. At around 360 K, EuNbO3 undergoes a first-order phase transition to a tetragonal symmetry (space group I4/mcm) with the NbO6 octahedral tilting about the pseudocubic four-fold axis. As the temperature is further increased, the I4/mcm tetragonal phase changes into the Pm 3 ¯ m cubic aristotype at 460 K. The tetragonal-to-cubic transformation is characterized as a continuous phase transition.

Pb2Cu(OH)2I3 is a new type of halocuprate(I) that is a framework of alternating [Pb4(OH)4]4+ and [Cu2I6]4− units. The structure has been determined in orthorhombic space group Fddd to R1=0.037, wR2=0.057, GoF=1.016. Unit cell parameters are a=16.7082(9) A, b=20.8465(15) A, c=21.0159(14) A, V=7320.0(8) A3 (Z=32). There is no synthetic counterpart. The structure is based upon a cubane-like Pb4(OH)4 nucleus that is coordinated to sixteen iodide ions. Cu+ ions are inserted into pairs of adjacent edge-sharing tetrahedral sites in the iodide motif to form [Cu2I6]4- groups. The Raman spectrum of Pb2Cu(OH)2I3 has two O-H stretching modes and as such is consistent with space group Fddd, with two non-equivalent OH groups, rather than the related space group I41/acd which has only one non-equivalent OH group. Consideration of the 18-electron rule implies that there is a Cu=Cu double bond, which may be consistent with the short Cu…Cu distance of 2.78 A, although the dearth of published data on the interpretation of Cu…Cu distances in halocuprate(I) compounds does not allow a clear-cut interpretation of this interatomic distance. The orthorhombic structure is compared with that of the synthetic halocuprate(I) compound Pb2Cu(OH)2BrI2 with space group I41/acd and having chains of corner-linked CuI4 tetrahedra rather than isolated Cu2I6 pairs. The paired motif found in Pb2Cu(OH)2I3 cannot be achieved in space group I41/acd and, conversely, the chain motif cannot be achieved in space group Fddd. As such, the space group defines either a chain or an isolated-pair motif. The existence of Pb2Cu(OH)2I3 suggests a new class of inorganic halocuprate(I)s based upon the Pb4(OH)4 group.

This article reports two new Hf-rich intermetallics synthesized using Sn flux: Hf 3 Fe 4 Sn 4 and Hf 9 Fe 4− x Sn 10+ x . Hf 3 Fe 4 Sn 4 adopts an ordered variant the Hf 3 Cu 8 structure type in orthorhombic space group Pnma with unit cell edges of a =8.1143(5) A, b =8.8466(5) A, and c =10.6069(6) A. Hf 9 Fe 4− x Sn 10+ x , on the other hand, adopts a new structure type in Cmc 2 1 with unit cell edges of a =5.6458(3) A, b =35.796(2) A, and c =8.88725(9) A for x =0. It exhibits a small amount of phase width in which Sn substitutes on one of the Fe sites. Both structures are fully three-dimensional and are characterized by pseudo one- and two-dimensional networks of Fe–Fe homoatomic bonding. Hf 9 Fe 4− x Sn 10+ x exhibits antiferromagnetic order at T N =46(2) K and its electrical transport behavior indicates that it is a normal metal with phonon-dictated resistivity. Hf 3 Fe 4 Sn 4 is also an antiferromagnet with a rather high ordering temperature of T N =373(5) K. Single crystal resistivity measurements indicate that Hf 3 Fe 4 Sn 4 behaves as a Fermi liquid at low temperatures, indicating strong electron correlation.

Colloidally synthesized quantum dots of CsPbBr3 are highly promising for light-emitting applications. Previous reports based on benchtop diffraction conflict as to the crystal structure of CsPbBr3 quantum dots. We present X-ray diffraction and PDF analysis of X-ray total scattering data that indicate that the crystal structure is unequivocally orthorhombic (Pnma).

We report on single crystal growth and characterisation of binary intermetallics TaxGay. Single crystals were obtained from mixtures of the elements which were handled under various conditions. Several new compounds were identified. The highest Ga-content is found for the new binary phases Ta6Ga31 and Ta8Ga41. Both compounds evolve as intergrown crystals. Ta8Ga41 belongs to the V8Ga41 type (R 3 ¯ , Z=3, a=14.311 A, c=15.344 A), Ta6Ga31 to the triclinic Mo6Ga31-type (P 1 ¯ , Z=2, a=9.697 A, b=9.698 A, c=14.879 A, α=87.18°, β=80.83°, γ=85.18°). TaGa3 bases on the tetragonal TiAl3-type (I4/mmm, Z=2, a=3.769 A, c=8.718 A) but shows stacking faults leading to an increased Ta content Ta1+xGa3–x. This interpretation is supported by the structure model of an orthorhombic superstructure with an idealized composition Ta2Ga5 (Cmcm, Z=4, a=3.769, b=31.37, c=3.770 A). Ta2–xGa5+x (x≈0.38) is a representative of the Mn2Hg5-type (P4/mbm, Z=2, a=9.3213(13), c=2.7572(6) A). Ta4Ga5 represents a new compound with a novel crystal structure (P4/mbm, Z=16, a=11.793(2), c=16.967(3) A). The complex structure contains polyhedra with coordination numbers between 11 and 14. Ta3Ga2 (P42/mnm, Z=2, a=6.8382(4), c=3.4963(2) A) belongs to the U3Si2 type. For the composition Ta5Ga3 three different structure types were confirmed but with some differences. The tetragonal W5Si3 type (I4/mcm, Z=4, a=10.2199(7), c=5.1121(4) A) is a stoichiometric binary compound, the hexagonal Mn5Si3-type (P63/mcm, Z=2, a=7.7023(4), c=5.3062(3) A) contains a small amount of oxygen (Ta5Ga3O0.4) and in the tetragonal Cr5B3-type (I4/mcm, Z=4, a=6.5986(9), c=11.931(2)A) one of the Ga-sites shows a significant underoccupation of 40% (“Ta2.2Ga”). Compositions were confirmed by EDX measurements.

Two new non-centrosymmetric (NCS) n = 3 layered perovskites, RbBi2Ti2NbO10 and CsBi2Ti2TaO10, have been synthesized through high temperature solid state reactions. X-ray diffraction analyses suggest that RbBi2Ti2NbO10 crystallizes in the orthorhombic polar space group, Ima2 (No. 46), whereas CsBi2Ti2TaO10 crystallizes in the tetragonal nonpolar space group, P4 (No. 81). Interestingly, CsBi2Ti2TaO10 is the first Dion–Jacobson (DJ)-type layered perovskite with a NCS nonpolar space group. Powder second-harmonic generation (SHG) measurements with 1064 nm radiation reveal that both of the reported materials have SHG efficiencies of approximately 100 times that of α-SiO2 and are phase-matchable (type I). Piezoelectricity measurements suggest that the estimated d33 values for polar RbBi2Ti2NbO10 and nonpolar CsBi2Ti2TaO10 are 170 and 67 pm V–1, respectively. The net polarization direction arising from the constituent distorted polyhedra and the key component causing microscopic deformations in NCS structure are...

Three new ternary rare-earth zirconium chalcogenides, Ce 2 ZrSe 5 ( 1 ), Pr 2 ZrSe 5 ( 2 ) and Nd 2 ZrSe 5 ( 3 ), have been synthesized by a facile solid-state route with boron as the reducing reagent. They crystallize in the space group Pnma of the orthorhombic system, belonging to the U 3 Se 5 structure type. Their 3-D structures are constructed by parallel polyanionic {[ZrSe 5 ] 6– } n chains and LnSe 8 bicapped trigonal prisms. The magnetic susceptibilities' data indicate their antiferromagnetic-like behavior without magnetic order down to 2 K. The structural relationships among several similar structures are discussed, together with the lanthanide contraction in the Ln 2 ZrSe 5 system.

Here, we review the advances in understanding the structure and properties of magnetoelectric gallium ferrite (GaFeO3 or GFO). Special significance of GFO lies in its compositional tunability over a large range of Ga:Fe ratio without forming a second phase which also renders prospective room temperature magnetoelectricity in the material. Detailed structural studies show noncentrosymmetric orthorhombic Pc21n symmetry without any structural phase transition between 4 K and 700 K. The material shows a ferrimagnetic behavior driven by cation site disorder, corroborated both experimentally as well as theoretically, with transition temperature dependent upon Ga:Fe ratio. GFO exhibits magnetostructural and magnetoelectric coupling indicating coupling among the structural, magnetic and electrical degrees of freedom which could possibly be utilized to strain engineer electrical and magnetic properties in the thin film structures. However, the biggest challenge remains to reduce the leakage in the material in both...

The soluble molecular selenophosphate salts ACsP2Se8 (A = K, Rb, Cs) crystallize in the orthorhombic space group Ccce with a = 14.982(3) A, b = 24.579(5) A, and c = 13.065(3) A for the Cs salt and a = 14.782(3) A, b = 23.954(5) A, and c = 13.044(3) A for the K analogue. ACsP2Se8 is composed of the molecular 6-membered ring, [P2Se8]2−, in the twist conformation charge balanced by alkali metals. The band gaps of these compounds are 2.44 ± 0.2 eV for Cs2P2Se8, 2.41 ± 0.2 eV for RbCsP2Se8, and 2.36 ± 0.2 eV for KCsP2Se8. The amorphous versions of these materials can be made by water quenching the melt and have band gaps for all ACsP2Se8 of 2.12 ± 0.2 eV. Raman spectroscopic studies exhibit active modes of PSe4 and Se−Se in the compound. Solution 31P NMR studies shed light into the interesting conformational fluxionality of the [P2Se8]2− anion, including a conformation that has not been previously observed. Thermal analysis reveals ACsP2Se8 exhibits a phase transition, which we investigate by in situ synchrotr...

The four ternary arsenides ATt3As3 (A=K, Rb; Tt=Ge, Sn) were obtained by reaction of the elements at 600–650 °C. They adopt an orthorhombic structure (space group Pnma, Z=4, with cell parameters ranging from a=9.9931(11) A, b=3.7664(4) A, c=18.607(2) A for KGe3As3 to a=10.3211(11) A, b=4.0917(4) A, c=19.570(2) A for RbSn3As3) containing corrugated [Tt3As3] layers built from Tt-centred trigonal pyramids and tetrahedra forming five-membered rings decorated with As handles. They can be considered to be Zintl phases with Tt atoms in +4, +3, and +1 oxidation states. Band structure calculations predict that these compounds are semiconductors with narrow band gaps (0.71 eV in KGe3As3, 0.50 eV in KSn3As3).

The intermetallic Nd 8 Co 4− x Al x Ge 2 C 3 ( x ≈0.65) was prepared from reaction of germanium and carbon in Nd/Co eutectic flux in an alumina crucible. This phase exhibits a new structure type in orthorhombic space group Pbcm , with unit cell parameters a =8.001(1) A, b =11.696(2) A, c =15.020(3) A ( Z =4; R 1 =0.0234). The structure features germanium-centered neodymium clusters Ge@Nd 9 which share faces to form layers separated by zigzag chains of cobalt atoms capped by carbon. Density of states calculations confirm that this compound is metallic, and indicate that the cobalt should not have a magnetic moment. This is supported by magnetic susceptibility measurements which show a low temperature ferromagnetic ordering at T C =50 K due to the Nd 3+ ions. Magnetization field dependence studies on single crystals indicate this compound is a strong ferromagnet with large anisotropy; the Nd 3+ magnetic moments align along the a -axis.

In this work, the solid solution series Ba2In2–xIrxO5+δ (x = 0–1.4, 2) was synthesized, and its structural, magnetic, and charge-transport properties were measured. With increasing Ir content, three transitions in the room-temperature structure were observed: orthorhombic to tetragonal to cubic to a monoclinic distortion of a hexagonal BaTiO3 structure. Neutron diffraction shows Ba2In1.6Ir0.4O5.4 to be cubic and Ba2InIrO6 to be monoclinic, the latter contrary to previously published X-ray diffraction refinements. Magnetization measurements show Curie–Weiss behavior for x = 0.2–0.6, which arises from nearly 50:50 ratio of Ir(V) and Ir(VI). To our knowledge, this is the first time Ir(VI) has been stabilized with standard solid-state methods under ambient conditions. The electrical resistivity measurements show all the compounds studied are semiconducting and that resistivity decreases with increasing Ir content, suggesting the proximity to a metal–insulator transition. A sign reversal in the high-temperatur...

The new intermetallic compound Sr2Pd4Al5 was prepared from the elements by reaction in niobium ampoules. The structure was refined from single-crystal data, which indicate the formation of a new structure type in the orthorhombic crystal system [a = 1814.49(10), b = 431.64(4), c = 1102.47(4) pm] with space group Pnma (wR2 = 0.0251, 1666 F2 values, 68 parameters). Full ordering of the transition-metal and aluminum sites was observed. The compound can be described as a polar intermetallic phase with a polyanionic [Pd4Al5]δ– network; however, a quite unique bonding situation was found within this framework. In addition to the usual Pd–Al bonding, significant contributions to the stability of the framework caused by homoatomic Pd–Pd and Al–Al interactions can also be found. Structural relaxation confirmed the electronic stability and predicted the compound to be a metallic conductor.

La2Re3B7 and La3Re2B5 have been synthesized in single-crystalline form from a molten La/Ni eutectic at 1000 °C in the first example of the flux crystal growth of ternary rare-earth rhenium borides. Both compounds crystallize in their own orthorhombic structure types, with La2Re3B7 (space group Pcca) having lattice parameters a = 7.657(2) A, b = 6.755(1) A, and c = 11.617(2) A, and La3Re2B5 (space group Pmma) having lattice parameters a = 10.809(2) A, b = 5.287(1) A, and c = 5.747(1) A. The compounds possess three-dimensional framework structures that are built up from rhenium boride polyhedra and boron–boron bonding. La3Re2B5 features fairly common B2 dumbbells, whereas La2Re3B7 has unique one-dimensional subunits composed of alternating triangular B3 and trans-B4 zigzag chain fragments. Also observed in La3Re2B5 is an unusual coordination of B by an octahedron of La atoms. Electronic band structure calculations predict that La2Re3B7 is a semimetal, which is observed in the electrical resistivity data as ...

Simple hydrolysis of CdF2 with aqueous KOH solution at room temperature for 24 h resulted in monophasic Cd(OH)F. It was characterized by high resolution powder X-ray diffraction, FTIR, Raman and UV–vis, photoluminescence spectroscopy techniques. The powder X-ray diffractogram was well fit in the orthorhombic space group (P212121), with a = 4.8298 (19) A, b = 5.5168 (23) A and c = 6.8456 (25) A. Both FTIR and Raman spectra confirmed the formation of Cd(OH)F. Strong absorption in the UV region was observed suggesting it to be a good UV blocker material. Optical band gap of 4.35 eV has been estimated for the sample. It showed luminescence in the purple and blue regions. It has been demonstrated as an efficient heterogeneous catalyst, for the degradation of aqueous dye solutions of Malachite Green (MG), Methylene Blue (MB), Rhodamine B (Rh B) and Rhodamine 6 G (Rh6G) UV radiation showing high recyclability. 4% F-doped CdO in cubic symmetry resulted from heating experiments of Cd(OH)F at 450 °C.

By applying high temperature (1270 K) and high pressure (3.5 GPa), significant changes occur in the structural volume and crystal topology of ThMo2 O8 , allowing the formation of an unexpected new ThMo2 O8 polymorph (high-temperature/high-pressure (HT/HP) orthorhombic ThMo2 O8 ). Compared with the other three ThMo2 O8 polymorphs prepared at the ambient pressure (monoclinic, orthorhombic, and hexagonal phases), the molar volume for the quenched HT/HP-orthorhombic ThMo2 O8 is decreased by almost 20 %. As a result of such a dramatic structural transformation, a permanent high-pressure quenchable state is able to be sustained when the pressure is released. The crystal structures of the three ambient ThMo2 O8 phases are based on three-dimensional (3D) frameworks constructed from corner-sharing ThOx (x=6, 8, or 9) polyhedra and MoO4 tetrahedra. The HT/HP-orthorhombic ThMo2 O8 , however, crystallizes in a novel structural topology, exhibiting very dense arrangements of ThO11 and MoO4+1 polyhedra connecting along the crystallographic c axis. The phase transitions among all four of these ThMo2 O8 polymorphs are unveiled and fully characterized with regard to the structural transformation, thermal stability, and vibrational properties. The complementary first principles calculations of Gibbs free energies reveal the underlying energetics of the phase transition, which support the experimental findings.

Two new metal chalcoiodides were synthesized by solid-state reactions at 400 °C. Crystal Data: Bi2CuSe3I, 1, monoclinic, C2/m, a=14.243(2) A, b=4.1937(7) A, c=14.647(2) A, β=116.095(2)°, V=785.7(2) A3, and Z=4; Bi6Cu3S10I, 2, orthorhombic, Pnma, a=17.476(2) A, b=4.0078(4) A, c=27.391(2) A, V=1918.5(3) A3, and Z=4. Compound 1 adopts a three-dimensional structure formed by two alternative layers, which consist of BiSe5 square pyramids, BiSe4I2 octahedra, CuSe4 tetrahedra, and CuSe2I2 tetrahedra. Compound 2 possesses a new open framework built up of BiS5 square pyramides, BiS6 octahedra, BiS8 polyhedra, and CuS4 tetrahedra where I− anions are uniquely trapped within the tunnels. Both electronic structures reveal that bismuth and chalcogenide orbitals dominate the bandgaps. The Cu d and I p states contribute to the top of valence bands, in which the distribution of I orbitals may correspond to the relative bonding interactions in 1 and 2. The optical bandgaps determined by the diffuse reflectance spectra are 0.68 eV and 0.72 eV for 1 and 2, respectively. 1 is a p-type semiconductor with high Seebeck coefficients of 460–575 μV/K in the temperature range of 300–425 K. The electrical conductivity is 0.02 S/cm at 425 K for the undoped sample. The thermal conductivity is 0.22 W/mK at 425 K.

A new bismuth-containing layered perovskite of the Ruddlesden–Popper type, K2.5Bi2.5Ti4O13, has been prepared by solid-state synthesis. It has been shown to hydrate to form stoichiometric K2.5Bi2.5Ti4O13·H2O. Diffraction data show that the structure consists of a quadruple-stacked (n = 4) perovskite layer, with potassium ions occupying the rock salt layer and its next-nearest A site. The hydrated sample was shown to remove the offset between stacked perovskite layers relative to the dehydrated sample. Computational methods show that the hydrated phase consists of intact H2O molecules in a vertical “pillared” arrangement bridging across the interlayer space. Rotations of H2O molecules about the c axis were evident in molecular dynamic calculations, which increased in rotation angle with increasing temperature. In situ diffraction data for the dehydrated phase point to a broad structural phase transition from orthorhombic to tetragonal at ∼600 °C. The relative bismuth-rich composition in the perovskite bloc...

The compound Cr4US8 has been synthesized at 1073 K and its crystal structure has been determined at 100 K. The structure is modulated with a two-fold commensurate supercell. The subcell may be indexed in an orthorhombic cell but weak supercell reflections lead to the monoclinic superspace group P21/c(α0γ)0s with two Cr sites, one U site, and four S sites. The structure comprises a three-dimensional framework of CrS6 octahedra with channels that are partially occupied by U atoms. Each U atom in these channels is coordinated by eight S atoms in a bicapped trigonal-prismatic arrangement. The magnetic behavior of Cr4US8 is complex. At temperatures above ~120 K at all measured fields, there is little difference between field-cooled and zero field-cooled data and χ(T) decreases monotonously with temperature, which is reminiscent of the Curie–Weiss law. At lower temperatures, the temperature dependence of χ(T) is complex and strongly dependent on the magnetic field strength.

Ca0.5Sr0.5Nb2O6 (CSN), a novel compound with crystal structure similar to the well-known orthorhombic columbite compound CaNb2O6 (CN) of alkaline earth niobates family was synthesized by a simple co-precipitation technique. The synthesized material was characterized by using X-ray diffraction (XRD) technique, transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectroscopy, FTIR spectroscopy, and photoluminescence emission spectroscopy. It was found that the CSN compound stabilizes in P b c n space group with the improved symmetry as compared to the CN. The lattice parameters of CSN were found to be comparable with those of CN, and they are: a = 15.013 A, b = 5.757 A and c = 5.198 A. The morphology of CSN and CN particles synthesized by a similar method was found to be identical. However, in CSN stronger self activated luminescence than that of CN was observed. The self-activated luminescence property of CSN was assigned to the niobate octahedral group [NbO6]7− similar to the CN.

Due course of study of the Th–Ni–Al system, new Th 2 Ni 10 Al 15 phase was revealed. Despite the prolonged heat treatment– the studied alloy did not attained equilibrium and contained many intermetallic phases along with the phase of an interest. Thus, structure solution of this phase was performed by only viable option – electron crystallography, specifically electron diffraction tomography. Such structures (containing actinides, transition metals and Al) were never solved before using this method. Since it is possible that Th, as heavy scatterer, will smear the Fourier map, making it hard to find the positions of the Al atoms – case study was performed prior structure solution of the Th 2 Ni 10 Al 15 phase. Finally, it was determined that the Th 2 Ni 10 Al 15 structure has an orthorhombic unit cell with following lattice parameters a = 3.99 A, b = 11.18 A, c = 17.34 A and I mmm (No.71) space group. Its structural model contains 54 atoms in the unit cell, distributed over 10 unique atom positions. This structure can be described both as stacking of coordination polyhedra formed around heavy atoms and as layered structure with unique architecture.

Phase-pure orthorhombic α′- and monoclinic β-Sr2SiO4 and its Ce3+- or Eu2+-doped versions are prepared by reaction of stoichiometric amounts of SrCO3, SiO2, CeO2 or Eu2O3 in the presence of 1 wt% H3BO3 or 1—50 wt% SrCl2 as fluxes in different atmospheres (1200—1400 °C, 4 h; in air, vacuum, 5% H2/N2, or 25% H2/N2).

(Et2NH2)2[CuCl4] crystallizes in the orthorhombic space group P212121 with Z = 8 (single crystal XRD).

The structural changes of Y 2 Zr 2 O 7 under high pressure have been investigated by using angle-dispersive synchrotron X-ray powder diffraction up to 34 GPa at room temperature. A new pressure-induced phase transition from cubic ( Fm-3m ) structure to orthorhombic ( Pnma ) structure at 27.3 GPa is observed, and the phase transition is irreversible. The high-pressure orthorhombic ( Pnma ) phase has longer average cation–anion bonding distance than cubic ( Fm-3m ) structure which was proved by the increase of coordination number.

Pure orthorhombic MgTi2O5 nanocrystals are prepared by gelation of Mg(O-Ac)2 and Ti(O-Bu)4 in ethylene glycol (25 °C, 30 min) followed by sintering the dried gel in air (600 °C, 2 h; 45% yield).

The compounds Eu 5 In 2 Sb 6 and Yb 5 X 2 Sb 6 ( X = Al, Ga and In) have been synthesized by high frequency induction heating method. The compounds Eu 5 In 2 Sb 6 and Yb 5 X 2 Sb 6 crystallize respectively in the orthorhombic Ca 5 Ga 2 As 6 and Ba 5 Al 2 Bi 6 structure types, space group Pbam . The crystal structure of all the four compounds can be envisaged as a composition of infinite one dimensional [ X 2 Sb 6 ] 10− double chains arranged in parallel fashion along the [110] plane. The oxidation state of the rare earth atom has been deduced from the bond valence sum calculation on the structural data. The deduced values are found to corroborate well with the values that obtained from the magnetic susceptibility and the X-ray absorption near edge spectroscopy.

Four complex intermetallic compounds BaAu6±xGa6±y (x = 1, y = 0.9) (I), BaAu6±xAl6±y (x = 0.9, y = 0.6) (II), EuAu6.2Ga5.8 (III), and EuAu6.1Al5.9 (IV) have been synthesized, and their structures and homogeneity ranges have been determined by single crystal and powder X-ray diffraction. Whereas I and II originate from the NaZn13-type structure (cF104–112, Fm3c), III (tP52, P4/nbm) is derived from the tetragonal Ce2Ni17Si9-type, and IV (oP104, Pbcm) crystallizes in a new orthorhombic structure type. Both I and II feature formally anionic networks with completely mixed site occupation by Au and triel (Tr = Al, Ga) atoms, while a successive decrease of local symmetry from the parental structures of I and II to III and, ultimately, to IV correlates with increasing separation of Au and Tr on individual crystallographic sites. Density functional theory-based calculations were employed to determine the crystallographic site preferences of Au and the respective triel element to elucidate reasons for the atom dis...

Two magnesium silicate fluorides, Mg5(SiO4)2F2 (compound 1) and Mg3SiO4F2 (compound 2), have been successfully synthesized by solid-state reactions for the first time. Compound 1 crystallizes in the space group P21/c (no. 14) of the monoclinic system, whereas the latter belongs to the space group Pnma (no. 62) of the orthorhombic system. As for the crystal structure, compound 1 can be described on the basis of a “framework” made by Mg1O4F2 and Mg2O5F octahedra forming many rings, in which the Mg3 and Si atoms reside. Compound 2 can also be described as the rings created by Mg2O4F2 octahedra, in which the Mg1 and Si atoms reside. Thermal analysis and the infrared spectrum of compound 1 were measured. In addition, the UV-Vis-NIR diffuse-reflectance spectrum exhibits that the relatively wide band gap is about 5.32 eV for compound 1, which is consistent with the theoretical value. The band structure and linear optical properties of title compounds are also theoretically calculated.