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Rod shaped structures of molybdenum trioxide (MoO3) were synthesized at low temperature using simple and low cost method. The synthesized materials were characterized by different characterization techniques. The effect of annealing temperature on crystal structure and optical properties of MoO3 was investigated. The hexagonal phase (h-MoO3) was observed up to 300 °C and beyond this temperature, the phase of the MoO3 is changed to orthorhombic (α-MoO3). The transition of crystal phase (h-MoO3 to α-MoO3) was investigated by analyzing the X-ray diffraction (XRD), Raman and DSC measurements. The shift in the wavenumber position of 971 cm−1 (Mo–O stretching) peak with temperature also substantiates the phase transition in MoO3 structure. The shape of nanostructured MoO3 was modified with annealing temperature. The change in crystal phases and shapes with temperature may result defects in the structure, which essentially modify the structural and optical properties of the material. The photocatalytic properties of the synthesized materials were studied on methylene blue (MB) dye under UV-irradiation. The sample annealed at 400 °C (M4) show excellent photodegradation compared to other samples. It could be due to the combined effects of shape (helical) and defects (oxygen vacancies) present in M4, as supported by the electron paramagnetic resonance (EPR) measurements. Among the various radicals, OH plays an important role in photodegardation of the MB dye.

The present study is focused on the structural correlation of magneto-electric coupling that exists in polycrystalline TbMnO 3 . The X-ray diffraction patterns are collected at various conditions, which are (1) at 300 K without a magnetic field, (2) at 2 K without magnetic field and (3) at 2 K with 7 Tesla magnetic fields. The structural transition in TbMnO 3 has been observed at 2 K and some lattice modulation after applying the magnetic field at 2 K. The Rietveld refinement of TbMnO 3 confirms the orthorhombic phase with centrosymmetric space group Pnma at 300 K. We have observed that the inversion symmetry breaks at 2 K and the polycrystalline TbMnO 3 has been refined using a non-centrosymmetric orthorhombic space group which can be either Pn2 1 a or P2 1 ma. This structural transition confirms the presence of a ferroelectric phase at 2 K. After the application of 7 Tesla magnetic field, the signature of an incommensurate phase has been observed in polycrystalline TbMnO 3 at 2 K. The DC magnetization behaviour with temperature M(T) and field M(H) reveals the antiferromagnetic behaviour of polycrystalline TbMnO3 below 42 K. We have also measured magneto-dielectric property of polycrystalline TbMnO 3 at the low temperature, which confirms the strong magneto-electric coupling in polycrystalline TbMnO 3 below the transition temperature.

Perovskite-type GdCr1-xMnxO3 (0.0 ≤ x ≤ 0.4) nano-crystalline samples are synthesized using sol-gel auto combustion process. The effect of Mn-doping in GdCrO3is investigated in term of structural, morphological, optical and thermal properties. X-ray diffraction (XRD) patterns confirm orthorhombic crystal structure of all the samples. The lattice parameters bond lengths and bond angles as obtained from Rietveld refinement analysis are found to vary systematically with Mn concentration. The crystallite sizes as calculated from the Scherrer's equation are found to decrease with Mn content. The Williamson-Hall (W–H) analysis reveals that the crystallite sizes decrease whereas lattice strain, stress, and energy density become more with the increase in Mn doping except for x = 0.3.The particle size estimated using transmission electron microscopy (TEM) are consistent with that obtained through W–H analysis. Scanning electron microscopy (SEM) images with energy dispersive x-ray (EDX) analysis exhibit significant change in the surface morphology with Mn doping and ensure the elemental compositions of the samples. The Fourier transform infrared (FTIR) spectra of these samples confirm the formation of desired crystal structure with two main characteristic bands at 476 and 586 cm−1. The optical band gap is found to reduce whereas Urbach energy increases with the increase in Mn concentration. The values of refractive index decrease in the ultraviolet region as a function of wavelength for all the samples and minimizes at the main absorption peak position as observed in the UV/Vis. spectra. The value of heat capacity at constant pressure (Cp) decreases with Mn doping except for 30% Mn concentration. Therefore, the present investigation suggests that the properties of GdCrO3 system can be tuned with the appropriate doping of Mn for the potential applications.

LaTiSbO6:xEu3+ (x = 0∼)1.0) phosphor with a typical PbSb2O6-related structure was prepared through a facile solid-state ceramic routine, and morphology measurements and structural Rietveld refinements were conducted. Results show that LaTiSbO6:xEu3+ (x = 0–0.4) phosphors formed a single trigonal phase (T-phase, space-group of P-31 m, No.162). The increase of Eu3+ doping (x = 0.5–0.6) can induce the formation of a second phase formation, that is, orthorhombic structure (O-phase) with space-group Pnma (No. 62). Meanwhile, heavily doped LaTiSbO6:xEu3+ (x = 0.6–1.0) was crystallized into a single orthorhombic structure (O-phase). LaTiSbO6 had a direct transition and the band gap was 2.97 eV. The luminescence properties of LaTiSbO6:xEu3+ (x = 0–1.0) were investigated at different doping levels. Eu3+-doping remarkably modified the band structure, resulting in the blue-shift of optical absorption, and the intrinsic blue emission of LaTiSbO6 peaked at 465 nm. Doping concentration exerted interesting influences on the optical properties of the phosphors, such as narrowed band gap, tunable red-emitting, dominant blue excitation wavelength, and thermal stability of the luminescence. Eu3+ ion was applied as a spectroscopic probe for the investigation of the relationship between luminescence and crystal microstructure.

High efficient Na3(Lu1-xEux)(PO4)2 orthophosphates phosphors were synthesized by conventional solid state reaction method. The obtained phosphors crystallized in the orthorhombic system with the space group Pca21. Since the crystal structure of the phosphor is composed of isolated PO4 tetrahedra, the average distance between rare earth ions was distant. As the concentration of Eu3+ activator ion reaches to 100%, reduced Judd-Ofelt parameter ratio of Ω2/Ω4 implies the improvement of the symmetry environment around Eu3+ ion and from the prolonged lifetime of 5D0→7F2 transition we inferred no-concentration quenching in this phosphor. Furthermore, due to the better crystallinity of Na3Eu(PO4)2 phosphor compared to the mixed crystals Na3(Lu1-xEux)(PO4)2, the internal quantum efficiency of the Na3Eu(PO4)2 phosphor reaches the high value up to 99% under near-ultraviolet (393 nm) excitation. Temperature dependent emission spectra revealed that Na3Eu(PO4)2 phosphor possesses stable emission of 80% at 423 K compared to room temperature. Due to high quantum efficiency and excellent thermal stability, Na3Eu(PO4)2 has potential application as reddish-orange phosphors.

The single crystals of BaIn2Te4 have been synthesized at 1173 K using the sealed tube solid-state method. The polycrystalline sample of the compound was also synthesized by stoichiometric reaction of elements with intermittent grinding and annealing at 1123 K. The crystal structure of BaIn2Te4 has been established by single crystal X-ray diffraction study at 298(2) K. It crystallizes in space group D 2 h 20 −Cccm of the orthorhombic crystal system with unit cell dimensions of a = 7.1417(14) A, b = 12.034(2) A, and c = 12.107(2) A with four formula units. The structure of BaIn2Te4 is related to the tetragonal binary TlSe structure (space group: I4/mcm). The crystal structure of BaIn2Te4 features one-dimensional chains of 1 ∞ [In2Te42−] that are separated by filling of Ba atoms. Indium atoms in these chains are surrounded by four Te atoms that form distorted tetrahedron geometry around In atoms. This compound does not show any homoatomic bonding and is having a closed shell electronic configuration. Thus, it can be easily charge balanced as Ba2+(In3+)2(Te2−)4. The phase purity of the polycrystalline BaIn2Te4 sample was established by the powder X-ray diffraction study. The direct band gap of 1.36(2) eV was estimated from the optical absorption study at room temperature. This ternary compound is an n-type semiconductor as suggested by the negative sign of the Seebeck coefficients (S). The absolute value of S was found to be decreasing on heating the polycrystalline BaIn2Te4 sample. The temperature-dependent resistivity study confirmed the semiconducting nature of the BaIn2Te4 sample. The thermal conductivity (κtot) values of polycrystalline BaIn2Te4 were found to be extremely low and were decreasing with raising the temperature with the lowest value of 0.30 Wm−1K−1 at 965 K. Hence, BaIn2Te4 and its analogs with related structures could be promising materials for thermoelectric applications by further optimization of carrier concentrations to improve electrical transport properties.

The (1-x)CaTiO3-xBi0.5Na0.5TiO3 [(1-x)CT-xBNT), x = 0.1–0.6] microwave ceramics were studied by traditional solid-state method. Crystal structures, microstructures, microwave dielectric properties and impedance analysis of the as-prepared ceramics were investigated systematically. Refinement of X-ray diffraction patterns from all of the samples were pure orthorhombic structure with Pbnm space group. The Raman spectra of (1-x)CT-xBNT were in accord with the previous reports except that some abnormal modes appeared in high-wavenumber of 1200 cm−1-3400 cm−1. The microstructures were dominated by even grains and the average sizes increased gradually with an increase in Bi0.5Na0.5TiO3 (BNT) content. The microwave dielectric constant, er, improved from 184 to 487, and the quality factor, Q×f, decreased constantly from 6973 GHz to 157 GHz as the amount of BNT in (1-x)CT-xBNT increased. However, the temperature coefficient of resonant frequency, τf, was restricted to fluctuating from 680 ppm/°C to 820 ppm/°C due to that the oxygen octahedral was twisted. For analysis and modeling of impedance data of 0.7CT-0.3BNT ceramics, the most appropriate equivalent circuits were found to consist of a parallel resistor-capacitor-constant phase element (R-CPE-C). And the activation energy for grains, 1.8 eV, was different to that in the grain boundaries, 1.0 eV.

Novel ternary intermetallic phase Ce2RuGe was synthesized via arc-melting of the constituents and subsequent annealing at 700°С. Its crystal structure was determined from the powder X-ray diffraction data collected at room temperature. The compound crystallizes in the orthorhombic structure of a new type: space group Pmmn (No. 59), lattice parameters: a = 4.38235(5) A, b = 4.31818(5) A, c = 9.91496(15) A, Z = 2, Pearson symbol oP8. In the fully ordered unit cell of Ce2RuGe, there are two crystallographic positions for Ce atoms, single site with Ru atoms, and single site with Ge atoms, each with the multiplicity of two. The crystal structure is built of infinite zigzag-like chains of the Ru and Ge atoms, propagating along the [010] direction. The essential feature is a very short interatomic distance between the Ce1 atoms and the Ru atoms being equal to 2.226(2) A, while the Ce2–Ru distance is of regular length. This structural property gives rise to distinctive physical behavior of the compound that exhibits the coexistence of valence fluctuations associated with unstable 4f shell of the Ce1 ions and a long-range magnetic ordering that emerges in the Ce2 ions sublattice. As revealed by means of magnetization, heat capacity and electrical resistivity measurements, Ce2RuGe orders antiferromagnetically at TN = 12.0(1) K, and becomes ferromagnetic below TC = 8.5(3) K.

The magnetic properties and magnetic structures of the R2TGe6 compounds (T = Ni and Cu, R = Tb, Ho and Er) were studied by magnetometric and neutron diffraction measurements. All compounds have an orthorhombic crystal structure of the Ce2CuGe6-type and are antiferromagnetic with the Neel temperatures ranging from 6 K for Er2CuGe6 up to 42 K for Tb2NiGe6. Based on the neutron diffraction data the magnetic structures were determined for R2NiGe6 (R = Tb, Er) and R2CuGe6 (R = Ho, Er). In these compounds the magnetic moments localized on the rare earth element form a collinear commensurate magnetic structure. The magnetic unit cell is equal to the crystal one in R2NiGe6 (R = Tb, Er) while it is doubled along the a-axis (propagation vector k = (½, 0, 0)) in R2CuGe6 (R = Ho and Er). The obtained magnetic structures are discussed on the basis of competition between the RKKY-type interactions and influence of Crystalline Electric Field (CEF).

Enthalpies of formation of (Mn,X)-Co-Ge (X = Zr, Pd) system in different structural states were analyzed utilizing the semi-empirical Miedema's model combined with the geometric one. Substitution of Mn by Zr significantly improves glass forming ability of Mn-Co-Ge, with parent equiatomic alloy among them. Chosen half-Heusler alloys, which are thermodynamically stable for the mentioned elemental compositions, were obtained by arc-melting. The x-ray diffraction studies confirmed coexistence of orthorhombic NiTiSi-type and hexagonal Ni2In-type structures for parent MnCoGe alloy and (Zr, Pd)-substituted samples. Thermomagnetic curves and magnetic isotherms allowed to reveal the Curie temperature TC and a magnetic entropy change ΔSM and allowed to analyze the influence of both substitutive elements. The Curie temperatures are equal to 293 K for MnCoGe, 278 K for Mn0.9Zr0.1CoGe alloy and 318 K for Mn0.9Pd0.1CoGe. The maximum magnetic entropy change ΔSM values, calculated for the change of external magnetic field of about 5 T, amount to 6.17, 2.94, and 11.11 J (kg K)−1 for MnCoGe, Mn0.9Zr0.1CoGe and Mn0.9Pd0.1CoGe, respectively. Differences in magnetic characteristics of the analyzed alloys are mainly caused by the changes of extent of undergoing first order magnetostructural transition with Pd and Zr atoms substitution. The presence of Pd d moments is also beneficial for the enhancement of total magnetic moment and maximum value of magnetic entropy changes in Mn0.9Pd0.1CoGe alloy.

Lead-free piezoelectric (1-x)(0.96K0.46Na0.54Nb0.98Ta0.02O3-0.04Bi0.5(Na0.82K0.18)0.5ZrO3)-xCaZrO3+0.2%mol MnO ceramics sintered in reducing atmosphere ( p o 2 = 1 × 10−11 MPa) were prepared via conventional solid-state reaction methods. The grain size decreases from ∼1.08 μm to ∼0.25 μm. A phase transition from coexisting orthorhombic/tetragonal (O/T) phases to a rhombohedral (R) phase appears at x = 0.005–0.025 and induces a R/O/T phase boundary to form at x = 0.01. The ceramics at x = 0.01 show excellent piezoelectric properties (d33 = 270 pC/N and d∗33 = 490 p.m./V at 25 kV/cm) due to the R/O/T phases. Its outstanding unipolar strain reaches up to 0.162% at 35 kV/cm at room temperature, and its field-induced strain varies less than 10% from room temperature to 125 °C. CaZrO3 dopant improves the temperature stability (Te) of d∗33 from 115 °C to 165 °C. At x ≥ 0.01, the maximum amplitude (ηmax) of d∗33 decreases from 6.68% to 2.81%. The CaZrO3 dopant can widen the temperature range of kp from 130 °C to 273 °C.

It has become a focus to develop low-permittivity microwave dielectric materials to meet the needs of high-speed transmission in telecommunication devices. Here, we report two Ge-based microwave dielectric ceramics prepared using the conventional solid-state method, MgGeO3 and ZnGeO3, with low permittivity of 6.8 and 6.6, the high-quality factor of 65,200 GHz and 25,200 GHz, and negative temperature coefficient of −45 ppm/°C and −35 ppm/°C. Orthorhombic ilmenite structure of MgGeO3 can be obtained in the range of 1160–1240 °C. However, the single-phase ZnGeO3 is not available in air, and the ceramics sintered at 1040–1120 °C contain two phases of Zn2GeO4 and GeO2.

The effects of Co on the Cu-Ni-Co-Si alloys' microstructure and mechanical properties were investigated. The Cu-1.5Ni-1.0Co-0.6Si and Cu-1.5Ni-1.5Co-0.6Si alloys with combined aging and 40–80% cold rolling were also investigated. The hardness, electrical conductivity, and microstructure were characterized, complemented by X-ray diffraction analysis and transmission electron microscopy. At 450 °C alloys aging, the aging precipitated phases are β-Ni3Si and Co2Si. Specifically, the orthorhombic (Ni, Co)2Si precipitates were found, which have the same crystal structure as the Ni2Si precipitates. The crystal orientation relationship between the matrix and the precipitates is: [112]Cu//[112]β//[012]p, ( 1 1 ¯ 1 ) Cu// ( 1 1 ¯ 1 ) β//(021)p; [001]Cu//[001]β//[001]p, (220)Cu//(110)β//(100)p. With the increasing Co content, the properties of the alloy were degraded. However, Co can promote the growth of the precipitates and accelerate precipitation during the aging process. After aging at 500 °C for 2 h, the hardness and conductivity of the Cu-1.5Ni-1.0Co-0.6Si alloy with 40% deformation were 250 HV and 43% IACS, respectively.

A comparative study of the magnetocaloric effect and refrigerant capacitance properties of orthorhombic perovskite-like isostructural compounds RCrO3 (R: Yb, Er, Y and Sm) was carried out (R cations with and without a magnetic moment and different cation size). Two scales of values can be observed at the Cr3+ and R3+ ordering temperatures. A higher magnetocaloric effect near the rare earth ion ordering temperature with values ranging from − Δ S M ( T N Cr ) = [0.15 to 0.72] and a lower one at the Cr ordering temperature ranging from − Δ S M ( T N R ) = [-0.2 to 12.5]. A normal and an inverse magnetocaloric effect were observed in the low temperature regime for the case of Sm at and above the spin reorientation of the Cr ions. The evolution of − Δ S M with R3+ ion radius increase and with total paramagnetic system moment are also discussed.

In this account, La0.67(Ca0.3Sr0.03)MnO3:mol%Agx (LCSMO:Agx, 0 ≤ x ≤ 0.5) high-density composites were successfully prepared by the conventional sol-gel method using deionized water as solvent. The structures, surface morphologies and electrical transport properties of obtained composites were analyzed by various analytical methods. The X-ray diffraction (XRD) profiles of LCSMO:Agx exhibited single perovskite structure with pure orthorhombic crystal structure (Pnma space group) and without presence of traces secondary phases. Field emission scanning electron microscopy (FESEM), XRD and X-ray photoemission spectroscopy (XPS) depicted good grain surface connectivity of the specimens. In addition, grain size increased with Ag doping. The influences of Ag2O doping on materials electrical properties were also explored. The results indicated the presence of silver as Ag+ ions substituting A-site ions. Furthermore, small amounts of metallic silver gathered at the grain boundaries (GBs) were detected. This increased both the Mn O bond length and Mn O Mn bond angle, and slightly expanded both cell volume (V) and lattice constant (a, b, c). The maximum value of temperature coefficient of resistivity (TCR) reached 11.2% K−1 with peak TCR temperature (Tk) of 281.5 K. The improved electrical transport performances of LCSMO:Agx materials were attributed to Ag doping, which enhanced Mn4+ ion amounts and GBs connectivity in each specimen. In addition, excess replacement of A-site ions by Ag+ expanded the metal-insulator transition characteristics and reduced the temperature coefficient of resistivity. Finally, a double exchange based mechanism was proposed to explain the above results.

A new series of Fe2-xScxMo3O12 (x = 0, 0.4, 0.8, 1.2, 1.6) ceramics have been synthesized by the co-precipitation reaction method. The phase composition, microstructure, phase transition and thermal expansion behavior of the Fe2-xScxMo3O12 samples have been investigated using XRD, Raman, SEM, STEM, EDX, XPS and TMA. Results show that Fe3+ has been substituted by Sc3+ successfully. Single phase Fe2-xScxMo3O12 with Fe2Mo3O12-type monoclinic structure can be synthesized when 0 ≤ x ≤ 0.8. Fe2-xScxMo3O12 consisting of two phases with monoclinic and orthorhombic structures is found when x = 1.2 and will be completely transformed to Sc2Mo3O12-type orthorhombic structure when x = 1.6. Monoclinic-to-orthorhombic phase transition temperature of Fe2-xScxMo3O12 can be successfully reduced from 513 °C to below room temperature with increasing Sc3+-substitution content (x). The temperature range of Fe2-xScxMo3O12 showing negative thermal expansion can be significantly expanded. Moreover, Fe0.4Sc1.6Mo3O12 ceramics with orthorhombic structure displays stable negative thermal expansion property from 25 °C to 600 °C and its average linear coefficient of thermal expansion is measured to be −5.80 × 10−6 °C−1.

Polycrystalline compounds of Dy0.55Sr0.45Mn1-xFexO3 (x = 0.0–1.0: 0.2) were prepared by high temperature solid state reaction route. All the compounds were found to have orthorhombic structure with Pnma space group with four formula units per unit cell. However, for high iron content corresponding to 0.8 and 1.0, some impurity phases were present. Raman modes of the substituted compounds were found to shift to higher wave numbers as compared to x = 0.0. All the compounds displayed insulating property with variable range hopping type of conduction. Mossbauer spectroscopy studies performed at room temperature revealed the presence of both trivalent and tetravalent iron ions for high concentrations of iron. Sextet pattern observed for high iron content suggested the presence of a magnetic phase even at room temperature. Temperature variation of magnetization showed paramagnetic behavior in the high temperature region (>100 K) and displayed variety of magnetic structures below 100 K. Effective magnetic moments (μeff.) of the compounds were determined by fitting the molar susceptibility data in the paramagnetic state to Curie-Weiss law. Experimental effective magnetic moment values were found to be larger than the calculated μeff. values revealing ferromagnetic cluster formation.

Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramics with super large grain size (>50 μm) have been successfully fabricated by sol-gel method. The effects of pH value of precursor solution on microstructure, electric properties and fatigue behavior were systematically studied. BCZT ceramics with super large grain size (35–55 μm) were prepared by BCZT powders with large particle size (136–221 nm) by controlling the pH value. The grain size and densification of BCZT ceramics decrease with the increase of pH value of precursor solution. XRD results indicate that there is the coexistence of rhombohedral and tetragonal phase in BCZT ceramics synthesized by precursor solution with a pH of 3 and are the coexistence of orthorhombic and tetragonal phase in BCZT ceramics synthesized by precursor solution with a pH of 5 and 7. BCZT ceramics shows obvious diffuse ferroelectric-paraelectric phase transition characteristic and the diffuseness behavior enhances as the pH value increases. The remnant polarization and coercive electric field of BCZT ceramics reduce with the decreased grain size caused by the increase of pH value. The excellent piezoelectric properties (d33 = 585.6 pC/N and d33∗ = 898 pm/V) of BCZT ceramics have been obtained by super large grain size and the construction of phase boundary of tetragonal phase and orthorhombic phase. Furthermore, BCZT ceramics with large grain size still has high fatigue resistance to bipolar electric cycling.

Melt-spun Mn50Bi50-xSbx alloys with x ≤ 5 were prepared at different solidification rates and characterized both in the as-spun state and after annealing. In the as-spun alloys, the Sb substitution leads to the formation of a metastable phase, similar to the binary “quenched high-temperature phase” but without the superstructure of the latter and exhibiting a different – increasing – temperature dependence of coercivity. The new nanocrystalline metastable phase is not only itself characterized by a high room-temperature coercivity (in excess of 20 kOe), but upon annealing it transforms into a high-coercivity (up to 13.5 kOe) “low-temperature” α phase. However, the advantage of obtaining a high coercivity without the otherwise required milling made possible by the Sb substitution is undermined by the absence of a local crystallographic texture in the melt-spun alloys. The best combination of the isotropic hard magnetic properties realized for the Mn55Bi43.5Sb1.5 composition is a remanence of 35.5 emu/g and a coercivity of 8.1 kOe. The annealed Sb-free Mn50Bi50 alloys did possess a local crystallographic alignment and, for high solidification rates, a moderate coercivity up to 5.6 kOe; however, they had an inadequate “rectangularity” in the demagnetization curve. The orthorhombic compound known as MnBi0.9Sb0.1 and described earlier as antiferromagnetic was obtained in the annealed ribbons with x ≈ 5. The compound was found to order ferromagnetically between 200 K and ≈250 K and to exhibit a significant coercivity, 14.3 kOe at 50 K. It is suggested that the MnBi0.9Sb0.1 may actually be a Sb-stabilized “new phase” observed earlier as metastable in the Bi–MnBi eutectic alloys.

Organic-inorganic halide perovskite (OIHP) has attracted tremendous attention due to its potential applications in optoelectronics such as light emitting device and photodetector. Here, we have grown high quality CH3NH3PbBrxCl3-x perovskite single crystals and investigated the luminescence mechanism of these materials. The results indicate that optical properties of CH3NH3PbBrxCl3-x perovskite materials are strongly depend on the temperature and the dope concentration. Free exciton recombination emission has dominant contribution to luminescence spectra of materials at orthorhombic structure, as bound exciton recombination emission to the spectra of materials at cubic structure. Based on temperature-dependent photoluminescence, the exciton binding energy of CH3NH3PbCl3 and CH3NH3PbBr0.3Cl2.7 are calculated as about 22.9 meV and 27.1 meV, respectively.

Ovonic threshold switching (OTS) selector is a key technology for high-density crossbar memory array. The basic characteristics of GeSe OTS material including structural information, film properties, microscopic properties, and electrical threshold switching behaviors are investigated by combining ab-initio molecular dynamics and experiments. Amorphous GeSe contains numerous Ge Se covalent bonds and defective structure motifs. The original resistance is extremely high compared to phase change materials, leading to lower leakage currents in device cells. The structure of GeSe remains stable at ∼350 °C and transforms to orthorhombic phase at higher temperature up to 450 °C. The severe phase separation of 500°C-annealed GeSe is observed with Se crystal grains. The high threshold voltage (>4 V) and holding voltage (>1 V) with large fluctuation (>1 V) are presented in the OTS cells with GeSe material. Due to the comprehensive investigations of GeSe material, we can improve the thermal stability and device performance of GeSe as a base material to find promising candidates for crossbar memory.

In this work, we are interested in the new compounds Li1.5Rb0.5MoO4 preparation by the solid state method. Also, we present a comparative study with LiRbMoO4 and Li2MoO4. The X-ray powder diffraction indicates that these compounds crystallize at room temperature in the monoclinic, orthorhombic and trigonal systems with the P21, Pcab and R-3 space groups, respectively. The shapes of the grains for these ceramics were observed by means of scanning electron microscopy (SEM) images. The Tauc model was used to determine the optical gap energy (4, 4.3 and 3.9 ev) and the urbach energies (1.51, 0.35 and 1.14 ev) of our compounds. The electric and dielectric proprieties of Li1.5Rb0.5MoO4 have been studied. We carried out complex impedance spectroscopy in the frequency range 200 Hz-5 MHz at different temperatures (575–723 K). The complex impedance diagram showed a single semicircle, implying that the response originates corresponding to the grains. As a result, an electrical equivalent circuit has been proposed. The spectra follow the Arrhenius law with two energies of activation 1.58 eV for impedance measurements and 1.25 eV for that of modulus. The alternative current (AC) electrical conduction of the three compounds is governed by the overlapping large polaron tunneling (OLPT).

The Ni-Mo-Cr system is critical for the design of nickel-based superalloys. This system stabilizes different topologically close packed (TCP) phases which precipitate in many of the commercially used superalloys. A diffusion multiple approach was applied to map the phase diagram of the ternary system in a highly efficient manner. Two isothermal sections of the Ni-Mo-Cr system at 1100°C and 1250°C were constructed from the results obtained from diffusion multiples using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD). At both temperatures two TCP phases were observed, namely the tetragonal σ- and the orthorhombic P-phase. In the range of this study the σ-phase was found to be widely stable towards the Cr-poor side, whereas the P-phase was detected on the Ni-rich side. The phases were characterized mechanically by microhardness measurements. Determined values range from 8,5 to 9,2 kN/mm2 for σ- and P-phase. By analysing interdiffusion zones of quaternary systems the solubility limits of Re, Ru and W were determined and compared for both TCP phases in order to assess their stabilising impact. Maximum solubilities of up to 12,7 at.% were detected, whereas the P-phase exhibits higher solubility limits than the σ-phase. In both phases solubility limits decrease with increasing temperature. In contradiction to previous experience in nickel-based superalloys, the observed stabilising effect on TCPs in quaternary systems is stronger for Ru than for Re.

Multiferroic Bi(1+x)×0.85Nd0.15FeO3 (BNF) ceramics with various Bi contents are prepared by conventional solid state reaction, and the effects of excess Bi on the structure, morphology, dielectric, ferroelectric, and magnetic properties are investigated. XRD patterns show the coexistence of rhombohedral and orthorhombic phase in all BNF ceramics due to the doping of Nd3+ ions. Bi2Fe4O9 and Bi2O3 impurity can be observed in x = 0 and x = 5%, 7.5% ceramics, respectively. Surface morphologies are closely related to the Bi content and x = 2.5% sample exhibits the largest average grain size of ∼6.72 μm. The leakage current density has been decreased by 3–4 orders of magnitudes through excess Bi. The x = 2.5% sample shows good ferroelectric property with typical hysteresis loop and a large remnant polarization of about 42 μC/cm2 at 150 kV/cm. The P-E hysteresis deteriorates in x = 5% and x = 7.5% ceramics. The PbZrO3-like superstructure related to 1/4(hh0)p diffraction spots in SAED pattern can be found in all BNF ceramics and the number of grain with superstructure observed in each sample decreases as the Bi content increases. As Bi content increases, the remnant magnetization decreases at first, and then increases. Conversion-electron Mossbauer study have ruled out the impacts of Fe2+, Fe4+, or γ-Fe2O3 on the magnetic properties, suggesting that the weak ferromagnetism comes from the destroy of spin cycloid through substitution of Bi3+ ions with Nd3+ ions. Excessive Bi3+ ions have weakened the effect of Nd3+ ions on suppression of spin cycloid and resulted in the degradation of magnetic properties. The slight improvement of magnetic properties in x = 7.5% sample is considered to attribute to Fe vacancies induced by excessive Bi.

In this article, polycrystalline InSbS 3 thin films were fabricated successfully at first time on the n-Si wafer by spray pyrolysis system to produce InSbS 3 /n-Si heterojunction. The structural characterization of the InSbS 3 thin films was measured by FE-SEM and XRD techniques. The InSbS 3 thin films are polycrystalline with orthorhombic structure. The diode parameters of the InSbS 3 /n-Si heterojunction like the barrier height ( ϕ b ), series resistance ( R s ) and the ideality factor ( n ) were evaluated by measuring the I–V characteristic curve in the dark situations. The C–V analysis of the InSbS 3 /n-Si heterojunction illustrates the junction was abrupt. The efficiency of the InSbS 3 /n-Si device were evaluated from the J-V characteristics curve under illuminations and equal 3.82%

We report doping at B-Site in TmFeO3 with In3+ ion of varying concentration (x = 0.02, 0.05, 0.07, 0.1) to explore the effect of In3+ ion substitution on structural, magnetic and vibrational properties. XRD study revealed that all the synthesized samples exhibit distorted perovskite orthorhombic (Pbnm) crystal symmetry. The immediate observable effect was an increase in lattice parameters with increasing doping up from x = 0.0 to 0.1 as evidenced by diffraction peaks shifted towards lower angle. Spin reorientation transition (Γ4→Γ2) in all prepared samples occurs at temperature (∼85–92 K) to be a process involving the continuous rotation of Fe3+ spins. M-H curves display the coexistence of weak ferromagnetism and antiferromagnetic ordering at all the measured temperatures with reduction in coercive field and remanence values. Varied magnetic behaviors were observed in this series of compounds, which are believed to be associated with the different interactions of Fe and rare earth ions. The occurrence of two-magnon and two-phonon modes in Raman spectra at temperature around 100 K attributed to spin-reorientation transition exhibited by TmFe1-xInxO3. This might be unambiguous evidence for spin-phonon coupling in the prepared compounds. The coupling and possible presence of two phonon and magnon pair scattering and other energy carriers have been used to explain several recently discovered thermally driven spin transport phenomena.

We report the results of the studies on crystal structure, electronic structure and dielectric properties of Er1-xLaxFeO3 (ELFO) (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) orthoferrites synthesized by co-precipitation method. Rietveld refinement of the XRD data confirms the orthorhombic crystal structure for all the samples. The study of Fe L3,2 -edge X-ray Absorption spectroscopy shows the presence of Fe-ions in 3 + valence state in all the samples. Investigations on the dielectric behavior of ELFO samples over the wide frequency range of 20 Hz to 5 MHz show the increment in the dielectric constant with La-doping. ErFeO3 has the lowest value of dielectric constant whereas LaFeO3 has the highest value of dielectric constant among all the samples. Effect of grain and grain boundary contribution on the dielectric behavior is studied using complex dielectric permittivity. The observed colossal dielectric behavior in LaFeO3 is attributed to the combined contribution from the intrinsic dielectric constant of the material and that due to the modification in the microstructure.

We report pressure-induced structural instability and amorphization in compressed orthorhombic α-V2O5 by in situ synchrotron x-ray diffraction observations and Raman spectroscopy measurements in diamond-anvil cells up to 20.2 GPa and 21.9 GPa, respectively. In situ x-ray lattice parameters (a, b, c) and d-spacings at high pressure show that the orthorhombic α-V2O5 exhibits an apparent discontinuity at ∼4.3 GPa, indicating the occurrence of structural distortion upon compression. Upon further pressurization, the distorted α-V2O5 starts to be amorphizing at ∼12.6 GPa and becomes fully amorphous at ∼20.2 GPa, which is again confirmed by our high-pressure Raman spectroscopy measurements. This obtained amorphous V2O5 polymorph can be recovered at ambient conditions, showing that the pressure-driven distorted orthorhombic-to-amorphous phase transformation is irreversible. Moreover, Gruneisen parameters of various Raman modes for α-V2O5 are derived, which are in agreement with the previously experiential study by Arora et al. Our results might be important to understand the high-pressure behaviors in M2O5 polymorphs for their uses at extreme conditions.

The present work is concerned with synthesis of doped (Cd2+ ions) and surface passivated (ZnS) AgInS2 core/shell nanocrystals by hot-injection method. UV spectral analysis of the nanocrystals thus prepared revealed that compared to dopant, passivation does much better in enhancing the optical property. Among the nanocrystals that were prepared, the growth of shell over core (AgInS2/ZnS) enhanced the optical property of AgInS2 considerably compared to dopant on either core or shell or both core-shell of nanocrystal. On the contrary, photoluminescence study revealed that doped AgInS2 with surface passivation (AgInS2:Cd2+/ZnS) plays a critical role in increasing PL intensity compared to either dopant or passivation alone on AgInS2. This inference is based on the fact that passivation was accompanied by decrease in surface-to-volume ratio that led to change in surface structure and crystal morphology. From XRD measurements we found that all the synthesized nanocrystals exhibited orthorhombic crystal structure with slight change in diffraction peak positions. The diffraction peak was shifted to lower angle with Cd2+ ions dopant and higher angle with surface passivation. The change in diffraction pattern suggests the formation of AgInZnS/ZnS alloy of ZnS on AgInS2 core. TEM images of pure AgInS2/ZnS and doped core/shell nanocrystals revealed that both pure and doped core/shell were irregular and sparingly mono-dispersed nanoparticles. EDX spectrum clearly revealed that pure and doped AgInS2/ZnS nanocrystals were composed of Ag, In, S, Zn and Cd ions in the synthesized systems. The formation of AgInS2/ZnS core/shell nanocrystals were confirmed from the experimental results and these nanocrystals might be a good material in many optoelectronics industrials and bio-imaging application in near future.

In this study, we have investigated the temperature dependent structural, optical and dielectric properties of Cu2Se thin films that are nanosandwiched with 50 nm thick ytterbium slab (CYC). The X-ray diffraction monitoring of the films during the heating process in the temperature range of 293–473 K has shown that the CYC films which contain both of the cubic and orthorhombic phases in its structure exhibits lattice expansion that increases the grain size and decreases the defect density, stacking faults and microstrain by 12.5% and by 28.9%, 12.8% and 11.3%, respectively. The CYC films show enhanced permanent crystallinity presented by high degree of orientation with reduction of the weight of the orthorhombic phase after cooling. On the other hand, a red shift in the energy band gap value is observed during the heating process. The analysis of the temperature dependent optical properties has shown a good correlation between the lattice expansion and energy band gap narrowing. In additions, the CYC samples are observed to exhibit negative capacitance effect that nominates the material for use in electronic circuits. The negativity of the capacitance decreased with increasing temperature due to the reduction in the defect density.

Nanocrystalline samples of LaCr1-xCoxO3 (0 ≤ x ≤ 0.3), synthesized through the sol-gel process are characterized to investigate the effect of cobalt doping on various physical properties. The orthorhombic structure of the samples is verified by the XRD patterns. Lattice parameters are estimated using PowderX software and are found to follow the Vegard's law. Williamson Hall analysis is employed to compute the crystallite size and lattice strain. Crystallite sizes exhibit a decrease whereas lattice strain shows an overall increasing trend with the increase in Co concentration. The random dispersal of grains is recognized through scanning electron micrographs and the EDX analysis approves the purity of the samples. TEM analysis provides the particle size in the range of 10–30 nm. The presence of characteristic band in FTIR spectra confirms the formation of LaCr1-xCoxO3 (0 ≤ x ≤ 0.3) samples. UV/Visible analysis is used to calculate the energy band gap and other optical parameters and cobalt doping decreases the band gap considerably. Thermal analysis reveals the occurrence of structural transition for all the samples. Imaginary part of dielectric permittivity and loss tangent decrease with increase in the frequency and finally becomes constant at higher frequencies. The AC conductivity data obey the Jonscher's universal dynamic law and it is established that small polaron hopping is involved in the conduction mechanism. Electrical modulus increases with the rise in frequency indicating the short range mobility of charge carriers. Nyquist plots exhibit only one incomplete and distorted semi-circular plots for all the samples specifying that the relaxation process deviate from the ideal Debye type behaviour. Also, both the grains and charge carriers hopping give rise to the conduction phenomenon in these orthochromites.

Two new structural types of BaREGeO4(OH) and BaRE10(GeO4)4O8 (RE = Ho3+,Er3+) single crystals were synthesized via high-temperature and high-pressure hydrothermal synthesis. The BaREGeO4(OH) compounds were found to crystallize in the orthorhombic space group Pbca. BaHoGeO4(OH) is used as a representative of the family with cell parameters of a = 5.7175(2) A, b = 10.1556(5) A, c = 10.6189(9) A and V = 964.97(8) A3. The BaREGeO4(OH) structure contains a one-dimensional chain of rare-earth polyhedra linked through edge sharing of oxygen atoms. High density BaRE10(GeO4)4O8 crystals crystallize in the monoclinic space group C2/m and feature a sheet like arrangement of rare-earth oxide polyhedra with Keggin-like features. BaHo10(GeO4)4O8 is used as a representative of this structure type with cell parameters of a = 12.4533(8) A, b = 7.2008(5) A, c = 12.0034(8) A, β = 100.183(2)⁰ and V = 1059.43(12) A3. Barium polyhedra and isolated GeO4 units aid in connecting the rare earth oxide framework to extend it in three-dimensional (3-D) space. Characterization by single crystal X-ray diffraction and Raman and photoluminescence spectroscopies is reported.

RbEu(MoO4)2 is synthesized by the two-step solid state reaction method. The crystal structure of RbEu(MoO4)2 is defined by Rietveld analysis in space group Pbcn with cell parameters a = 5.13502(5), b = 18.8581(2) and c = 8.12849(7) A, V = 787.13(1) A3, Z = 4 (RB = 0.86%). This molybdate possesses its phase transition at 817 K and melts at 1250 K. The Raman spectra were measured with the excitation at λ = 1064 and 514.5 nm. The photoluminescence spectrum is evaluated under the excitation at 514.5 nm. The absolute domination of hypersensitive 5D0→7F2 transition is observed. The ultranarrow 5D0→7F0 transition in RbEu(MoO4)2 is positioned at 580.2 nm being 0.2 nm blue shifted, with respect to that in Eu2(MoO4)3.

The Tm3+, Yb3+ co-doped CaZrO3 phosphor samples have been synthesized through solid state reaction method in the absence and presence of alkali metal ions (i.e. Li+, Na+, K+). The X-ray diffraction (XRD) study shows the formation of CaZrO3 crystal with orthorhombic phase. The Tm3+, Yb3+ co-doped CaZrO3 phosphor emits intense upconversion emission in blue (474 nm) and NIR (799 nm) regions due to 1G4 → 3H6 and 3H4 → 3H6 transitions of Tm3+ ions, respectively on excitation with 980 nm radiation. The emission intensity is significantly enhanced in the presence of alkali ions due to charge compensation and asymmetry in the crystal field. The emission intensity in the case of Na+ co-doped phosphor is maximum and at 1 W pump power, it is increased by ∼44 and ∼31 times in blue and NIR regions, respectively as compared to without alkali ions co-doped phosphor. The downshifting emission in blue region has been observed due to oxygen vacancy and Tm3+ ions on excitation with 277 and 360 nm radiations which is enhanced significantly in the presence of alkali ions. Thus, the intense blue emission by this material is suitable for blue and white light emitting phosphors.

This study reports influences of Sm doping on the crystal structure, nanomechanical and ferroelectric properties of Bi1-xSmxFeO3 (BSFO) thin films. BSFO films of perovskite phase were deposited on Pt/glass substrates by pulse laser deposition (PLD). The structural analysis shows that the BSFO transforms from rhombohedral structure into orthorhombic structure with the phase boundary near x = 0.16. The structure morphology of the thin films determined by using SEM and AFM exhibited that the grain size and surface roughness are reduced with increasing Sm content in BSFO. The hardness and Young's modulus are obtained in the range of 7.7–10.1 GPa and 154.6–167.5 GPa, respectively. Ferroelectric properties with remanent polarizations (2Pr) and coercive fields (Ec) occur respectively in the ranges of 41–150 μC/cm2 and 327–450 kV/cm for x = 0.05–0.14. The enhanced ferroelectric properties can be attributed to the smooth interface and fine microstructure with small grain sizes in range of 30–200 nm. A double ferroelectric hysteresis P-E loop with a different nanomechanical properties is observed in the composition of x = 0.16 and is associated with the appearance of orthorhombic phase. The leakage behavior with mechanisms and nanomechanical characterizations are also studied as functions of Sm content.

Multiferroics materials have been intensively investigated for applications into photovoltaic cells. KBiFe2O5 (KBFO) emerged as a strong candidate for such applications since it exhibits low bandgap energy. It is usually orthorhombic at room temperature and pressure, however, phase diagrams investigations determined that it transforms into a monoclinic structure at high temperatures and pressures. This monoclinic structure has more interesting multiferroic and electronic properties for photovoltaic applications. In this paper, we obtained such monoclinic phase at room temperature and pressure and investigated its stability under pressure changes. We showed KBFO undergoes a new reversible first-order structural phase transition into an orthorhombic structure at high pressures as determined by synchrotron X-ray diffraction and Raman spectroscopy measurements.

Tuning the optical and electrical properties of WO3 via doping is an efficient strategy to improve its photoelectrochemical (PEC) water splitting activity. In this article, a simple hydrothermal method is utilized to fabricate Ta-doped WO3 nanotriangle thin films for the PEC water splitting applications. The doping of Ta converts the nanorod structure of undoped WO3 into nanotriangle morphology. During the synthesis, the Ta is doped to orthorhombic WO3·0.33H2O and converted to hexagonal phase via annealing. The presence of Ta in the WO3 lattice obstruct the reconstructive transformation of orthorhombic to monoclinic phase producing Ta-doped WO3 with hexagonal phase. The optimum amount of Ta (1.88 at%) causes the reduction in the band gap and increase the oxygen vacancies and carrier density in WO3 lattice. Compared to undoped WO3, Ta-doped WO3 nanotriangles exhibit higher photocurrent and incident photon to current efficiency values. Finally, the possible band structure is proposed for the Ta-doped WO3 based on the spectroscopic and electrochemical data. The results of the present work suggest that Ta doping alters the band edge positions of WO3 and has the potential to improve the PEC water splitting activity of WO3.

To improve the usability of the lead-free piezoactuators on a broader temperature range, it is essential to ensure the temperature stability of the electric-field-induced strain (EFIS). Herein, we tried to propose a new strategy to solve the problem of the temperature-dependent degradation of EFIS, which takes advantage of the synergistic effect between the diffuse phase transition and the electric-field-induced phase transition. A potential lead-free candidate (K, Na)NbO3 (KNN)-based with SrZrO3 is prepared and exhibits excellent performance with a unipolar strain of 0.12% at 3 kV mm−1 (the normalized strain d33* is 400 pm V−1) and maintain 90% and 85% at the 180 °C and 190 °C, respectively. In-situ X-ray diffraction (XRD) was used to ascertain the evolution of the crystal structures under electric fields. It can be found with the selected area electron diffraction (SAED) patterns, that the orthorhombic asymmetry is induced in the miniaturized domains, and further transform into the monoclinic phase (Mc). When removing the electric field, the phase recovered partly. This kind of phase construction and phase evolution under electric field stands a good chance of improving the temperature stability of EFIS as well as our expectation.

The first ternary intermetallic phase - Ni11.4+xZn19.8In14.9-y (0 ≤ x ≤ 0.2; 0 ≤ y ≤ 0.1) in the Ni-Zn-In system is presented. The structure of the phase has been analysed by single crystal X-ray diffraction. Due to the similar X-ray scattering factors for Ni and Zn, a combination of X-ray and neutron diffraction has been employed to identify accurate sites of Ni and Zn in the structure of the Ni-Zn-In phase. The phase is structurally complex and adopts a narrow homogeneity range. The structure crystallizes in the orthorhombic space group Cmcm (63) and contains 46 atoms per unit cell which bears all types of disorder phenomena (vacancies, mixed site occupancies, and positional disorders) that is typical for complex metallic alloys. The structure is mostly tetrahedrally close-packed and is generated mainly by two types of endohedral clusters: a 12-atom cluster that is closely related to an icosahedron and an 11-atom polyhedron that is related to twinned cuboctahedron. The phase is stabilized at valance electron concentration between 1.82 and 1.83 e/a.

Novel temperature stable Li3Mg2NbO6-xLiF (x = 0.5–8 wt %) ceramics with ultralow loss were fabricated by the solid-state reaction process. The influence of LiF addition on the sintering, grain growth and morphology, and improved microwave dielectric characteristics was investigated. A single orthorhombic Li3Mg2NbO6 structure could be confirmed by Raman spectra and XRD patterns. Dense and homogeneous microstructure could be obtained with ∼10 μm average grain size. Results demonstrated that the er values were relevant to bulk density and the high Q×f values were influenced by the large grain sizes. The τf values depend on porosity corrected dielectric constant. Notably, the remarkably desirable microwave dielectric characteristics: er = 15.4, Q×f = 100,000 GHz, τf = −3.1 ppm/°C were achieved for the Li3Mg2NbO6 ceramics with x = 6 wt% sintered at 925 °C, which could be applied for ultra-low loss LTCC applications.

Orthorhombic In0.5Sc1.5(MoO4)3 ceramics with 3 wt% MgO as sintering aid were synthesized via solid state method at various temperatures. The effects of sintering temperature and 3 wt% MgO additive on the microstructure, density and negative thermal expansion property of the In0.5Sc1.5(MoO4)3 ceramics were examined using XRD, SEM and TMA. The results indicate that the increase of twice-sintering temperature promotes densification, and the grain size grows from 1 μm to 7 μm. When the twice-sintering temperature is further raised to 1200 °C, impurity Sc2O3 is detected due to the decomposition of In0.5Sc1.5(MoO4)3. The introduction of MgO as a sintering aid strongly affects the densification and negative thermal expansion stability of the In0.5Sc1.5(MoO4)3 ceramics owing to the formation of the liquid phase MgMoO4. The In0.5Sc1.5(MoO4)3 ceramics with 3 wt% MgO show more stable negative thermal expansion, and their average linear coefficients of thermal expansion (CTEs) are all tested to be between 4 × 10 −6 °C−1 and 5 × 10 −6 °C−1 at 30–700 °C. The variable temperature XRD results reveal In0.5Sc1.5(MoO4)3 shows anisotropic negative thermal expansion. The average CTEs of In0.5Sc1.5(MoO4)3 along a, b and c-axis are calculated to be −4.86 × 10 −6 °C−1, 4.25 × 10 −6 °C−1 and -3.25 × 10 −6 °C−1, respectively, and the volumetric CTE is calculated to be −3.83 × 10 −6 °C−1 at 25–700 °C.

The electronic and magnetic structure of orthorhombic (o-) YMn0.5Fe0.5O3 (YMFO) epitaxial film (space group Pbnm) deposited on the YAlO3 (010) substrate have been investigated using linear polarization-dependent x-ray absorption spectroscopy and magnetization measurements. The magnetic-ordering temperature of around 280 K is observed in o-YMFO film. The x-ray absorption spectra at the Fe-K and the Mn-K edges indicate the existence of anisotropic crystal field in o-YMFO film, with the longest and shortest Fe–O and Mn–O bonds tend to align with the crystallographic b- and a-axis, respectively, whereas the medium Fe(Mn)–O bond is aligned with the c-axis. The experimental x-ray magnetic linear dichroism at the Fe-L2 edges demonstrate an unusual single antiferromagnetic axis of Fe3+ ions below magnetic-ordering temperature, while a multi antiferromagnetic axis is generally observed in o-RFeO3 (R = rare earth) thin films. Our configuration-interaction cluster calculations also reveal that the single antiferromagnetic axis of the Fe sublattice is aligned with the b-axis in o-YMFO film, whereas it is directed along the a-axis in the bulk o-YFeO3.

The critical need for clean energy has led to the development of lead-free electroceramics. However, lead-free antiferroelectrics seldom have been reported because of the difficulties in materials fabrication and their low electrical performance. In this work, we successfully synthesized lead-free antiferroelectric ceramics (1-x)AgNbO3-xCaZrO3 (x = 0.00–0.01) using the solid state reaction method in flowing oxygen (O2) atmosphere. Calcium zirconate (CaZrO3) dopant effectively stabilized the antiferroelectricity of silver niobate (AgNbO3) by dramatically decreasing the tolerance factor t. Additionally, we identified an orthorhombic Pbcm structure similar to that of pure AgNbO3. With the introduction of CaZrO3, phase transition temperatures M1–M2, M2–M3 and the freezing temperature Tf decreased. The shift of the M1–M2 phase transition temperature and Tf was the result of the restriction of the M1 phase due to CaZrO3 substitution. The compositions of x

The stability issue is very critical for organic hybrid perovskite CH3NH3PbI3 to be used in solar cell applications; whereas CsPbI3 is reported to be more stable than that of CH3NH3PbI3. In the present work, we attempt to substitute Cs+ in the organic hybrid perovskite CH3NH3PbI3 matrix to form Csx(CH3NH3)1-xPbI3 with 0 ≤ x ≤ 0.4 in ambient conditions i.e., at room temperature and in air via solid state reaction route. The structural studies reveal presence of both CH3NH3PbI3 (tetragonal, I4/mcm) and CsPbI3 (orthorhombic, Pnma) phases for x > 0. It is appearing that partial solid solution formation has occurred up to x = 0.2 but for x > 0.2, the composite formation dominates. The optical band gap is slightly increased by ∼0.02 eV with substitution. These compounds keep the basic feature of parent CH3NH3PbI3 along with stability of CsPbI3.

Bulk ceramics with high recoverable energy density (Wre) and energy efficiency (η) play a critical role in the development of pulsed power systems for miniaturization and lightweight. The orthorhombic phase (Pb,La)(Zr,Ti)O3-based antiferroelectric (AFE) ceramics have been regarded as one of the most promising candidates for pulsed power system applications due to their relatively high energy storage density and efficiency. However, the main drawback of orthorhombic phase (Pb,La)(Zr,Ti)O3-based AFE ceramics is relatively low dielectric breakdown strengthen (DBS), which has always restricted the improvement of energy storage density. In this study, an effectively method to increase DBS by the introduction of Mn has been proposed. The relative density of orthorhombic phase (Pb0.91La0.06)(Zr0.96Ti0.04)O3 (PLZT) ceramics was improved by Mn-doping. And the introduction of Mn can decrease the tolerance factor (t) of PLZT ceramics because the radius of Mn2+ is larger than that of B-site Zr4+/Ti4+, and thus enhancing antiferroelectricity. Meanwhile, the effects of Mn-doping on the phase structure, microstructure and dielectric properties of PLZT ceramics have been studied thoroughly in this study. It is found that the highest Wre of 7.65 J/cm3 is obtained at 1.0 mol% Mn-doped PLZT ceramic, which is obviously larger than that of undoped PLZT ceramic (5.71 J/cm3). These results suggest that the Mn-doped PLZT ceramics are potential energy storage materials in pulsed power systems.

We report on the structural, magnetic and transport properties of Ru doped Ni50−xRuxMn38Sb12 (x = 0, 3 and 4) alloys. The alloys are found to crystallize in orthorhombic phase for x = 0, orthorhombic plus cubic phase for x = 3 and purely cubic for x = 4 respectively, at room temperature. Extended x-ray absorption fine structure (EXAFS) spectroscopy confirms the orthorhombic and cubic structure for x = 0 and 4 respectively while x = 3 shows mixed austenite and martensite phases, at room temperature. Temperature dependent EXAFS data confirms, first order structural transition from cubic austenite phase to orthorhombic martensite phase occurs at 305 and 265 K for x = 3 and 4 respectively, upon cooling. This is in addition to the second order magnetic phase transition at 350, 330 and 326 K for x = 0, 3 and 4 respectively. The change in the magnetic entropy around the martensitic transition is found to be about 19.5 and 12.3 Jkg − 1 K − 1 for x = 3 and 4, while it is 7.0 Jkg − 1 K − 1 for x = 0. These values (for x = 3 and 4) are large when compared to Ni50Mn38Sb12 (7 Jkg − 1 K − 1 ). Exchange bias field is found to be 383, 362 and 240 Oe at 3 K for x = 0, 3 and 4 respectively. Temperature dependent resistivity of the alloys also confirms the first order phase transition. Magnetoresistance is found to be 9.0% for x = 3, 3.5% for x = 4 and 6.0% for x = 0 respectively near martensite transition. Large resistivity difference between martensitic and austenite phases is due to the difference in the carrier concentration by at least one order. Anomalous Hall contribution ρ x y AHE distinguishes martensite and austenite phases.

More reports about monoclinic-orthorhombic (m-o) phase transition of A2M3O12 are focusing on the influences of radius as well as electronegative of A3+. However, m-o phase transition temperatures (PTTs) of A2Mo3O12 do not always increase or decrease with radius/electronegative of A3+ (A-Sc, Al, Cr, In, Fe). Considering the combined influences of electronegativity and radius of A3+ as well as radius of O2−, a general formula of m-o phase transition temperature (PTT) could be obtained and used to estimate PTT of A2Mo3O12 with low relative error. Furthermore, a simple linear relationship between PTT of A2Mo3O12 and Dr1/4·De of A3+ and Mo6+ (radius difference Dr = rA-rMo, electronegativity difference De = eA-eMo) is obtained by considering the combined influences of A3+ and Mo6+. The results suggest that m-o PTT of A2Mo3O12 should relate to the combined influences of A3+ and Mo6+ rather than the only influence of A3+.

Requirements for substituting the current lead-based piezoelectric materials with lead-free ones are becoming increasingly strong from environmental concerns. In this article, we report piezoelectric properties, phase transitions and domain configurations of a dense 0.963(K0.48Na0.52)(Nb0.955Sb0.045)O3−0.037(Bi0.50Na0.50)HfO3 lead-free ceramic prepared through solid-state reaction by two-step sintering. It has a large piezoelectric coefficient d33 = 512 pC/N and a planner electromechanical coupling coefficient kp ≈ 0.54 at room temperature. Dielectric measurement indicates that rhombohedral-orthorhombic, orthorhombic-tetragonal, and tetragonal-cubic phase transitions upon heating process occur at −30 °C, 57 °C and 238 °C, respectively. X-ray diffraction analysis shows that the crystalline structure is dominantly of orthorhombic phase at room temperature. Domain configurations were investigated by acid etching technique. The poled ceramic shows domain patterns of long parallel stripes with hierarchical nanodomain structure existing in some broad stripes. The observed outstanding piezoelectric properties are ascribed to the rhombohedral-orthorhombic and orthorhombic-tetragonal phase transitions, and to the characteristic domain structure.

Formation of magnesium silicides on amorphous silicon by deposition of Mg at room temperature is studied by electron energy loss spectroscopy, differential reflectance spectroscopy and high resolution transmission electron microscopy. Optimal crystal structures of Mg silicides under high pressure are found by ab initio DFT calculations. These structures are related to the particular minima of enthalpy. Dielectric functions are calculated for these structures. The transitions from the cubic phase c-Mg2Si to orthorhombic o-Mg2Si at 5.6 GPa and then from o-Mg2Si to hexagonal h-Mg2Si at 22.3 GPa are predicted using the USPEX code. The experimental spectra and the data obtained from the calculated dielectric functions are mutually consistent. Optical reflectance is suitable for monitoring the growth and transformations of the phases during experiments. During Mg deposition onto amorphous Si, the o-Mg2Si phase forms first, then the c-Mg2Si phase grows upon it. The observed sequence of phase formation is related with the compression stress arising in the depth of the Mg-Si mixture.

Although Si is a promising anode material, the worse electric conductivity and volume expansion of Si are key bottlenecks. To solve these problems, we apply the ab-initio calculations to explore the structural feature, electrochemical and electronic properties of MoSi2. Two novel MoSi2 orthorhombic phases: TiSi2-type(Fmmm) and ZrSn2-type(Fddd) are predicted. MoSi2 markedly improves the elastic stiffness and volume deformation resistance of Si due to the formation of Mo Si bond. The calculated volume of MoSi2 is smaller than that of Si. Importantly, the calculated average open circuit voltage(Voc) of hexagonal(P6222), tetragonal(I4/mmm), orthorhombic(Fmmm) and orthorhombic(Fddd) structures is 2.87 V, 1.23 V, 1.25 V and 2.47 V, respectively. The reason is that the introduction of Mo improves the charge overlap between the conduction band and the valence band. The tetragonal and orthorhombic structures exhibit metallic behavior due to the localized hybridization between Mo-d state and Si-p state. Our work provides a new path to improve the electrochemical and electronic properties of Si.