Structural and magnetic properties of a novel compound with Y3(Fe, V)29 stoichiometry and disordered CaCu5-type structure

A novel phase with nominal composition Y₃Fe_27.5V_1.5 has been synthesized by arc melting elemental constituents, followed by annealing at 1123 K. The samples were analyzed by electron microprobe analysis and the stoichiometric composition was Y_3.04Fe_27.56V_1.44. X-ray diffraction from powder samples shows that the structure is of a disordered CaCu₅-type (Space Group: P6/mmm) with lattice parameters a=4.8769(1) Å, c=4.1729(3) Å. This disordered structure, revealed using standard difference Fourier methods, can be considered as a TbCu₇-type, containing iron dumbbell sites. The disorder is not restricted to the rare earth sites and the dumbbell atoms, but is observed at other sites as well. The stoichiometric formula derived by Rietveld analysis is Y_3.00(3)Fe_28.5(3). Magnetic measurements give a Curie temperature of 439(5) K, and a saturation magnetization of 156.4 and 125.5 A m² kg⁻¹ at 5 and 300 K, respectively. The anisotropy field is 4.76 T at 5 K and 2.43 T at 300 K. X-ray powder diffraction patterns of magnetically aligned powder samples indicate that the magnetocrystalline anisotropy is of easy plane type. This result is supported from the analysis of the magnetization measurements on aligned powders which give K₁<0, K₂>0 and K₁+2K₂<0, a result that confirms the easy plane anisotropy. Mössbauer spectra were also obtained and fitted with a model consistent with the disorder. The average hyperfine fields are 28.4 and 21.5 T at 4.2 and 300 K, respectively.     

Structure and magnetic properties of Gd3(Fe1−xTix)29 (x=0.011–0.034)

Single-phase compounds Gd₃(Fe_1−xTi_x)₂₉ (x=0.0110.034) have been synthesized. Gd₃(Fe_1−xTi_x)₂₉ crystallises in a monoclinic lattice with space group P2₁/c, and the crystal structure is refined by the Rietveld technique based on X-ray powder diffraction data. Thermomagnetic analysis indicates that the Curie temperature of the compounds ranges from 517 K to 538 K. The saturation magnetizations of the Gd₃(Fe_1−xTi_x)₂₉ (x=0.011, 0.022, 0.034) at 1.5 K are 103.6, 102.0 and 94.3 Am²/kg, and the anisotropy fields at 1.5 K are 6.0, 6.2 and 6.4T, respectively.     

Atmospheric pressure chemical vapour deposition and characterisation of crystalline InTaO4, InNbO4 and InVO4 coatings

The possibilities to grow crystalline complex InTaO₄, InNbO₄ and InVO₄ coatings as well as single oxide layers In₂O₃, Ta₂O₅, Nb₂O₅, and VO_x were investigated using aerosol assisted atmospheric pressure chemical vapour deposition technique. Indium(III) and niobium(IV) tetramethylheptanedionates, tantalum(V) tetraethoxyacethylacetonate and vanadium(III) acethylacetonate were used as precursors, monoglyme and toluene as solvents. The influence of deposition conditions and solution composition on elemental and phase compositions of layers was studied. Indium tantalate layers containing pure monoclinic InTaO₄ phase were obtained ex-situ, i.e., after high-temperature (800 °C) annealing of layers grown at lower temperature (500 °C). Films containing pure orthorhombic indium vanadate or monoclinic indium niobate phase may be prepared using both in-situ (600 °C) or ex-situ (deposition at 400 °C, annealing at 800 °C) approaches. Under optimised deposition conditions and solution compositions, Ni-doped InVO₄ and InTaO₄ films were also deposited and their photocatalytic activity was tested.     

Effect of N, C and B interstitial atoms on local bonding structure in mechanically activated TiH2/h-BN, TiH2/C, and TiH2/B mixtures

Mechanically activated TiH₂/h-BN, TiH₂/C and TiH₂/B mixtures was studied by temperature-programmed desorption, X-ray diffraction, transmission electron microscopy and X-ray emission spectroscopy. Ball milling in the presence of additives results in a modification of hydrogen occupation sites. Additional Ti-N, Ti-C or Ti-B bonds from chemical bonding of Ti with interstitial N, C and B atoms, are formed in TiH₂ due to contact of TiH₂ nanoparticles with the respective additive matrix materials. Mixed configurations around Ti atoms with proportional combination of local Ti-H and Ti-N, Ti-C or Ti-B bonds significantly decrease the thermal stability of TiH₂. The effect is most pronounced when boron is the additive.     

Characterization of BaSnO3-based ceramics: Part 1. Synthesis, processing and microstructural development

The compound BaSnO₃ together with its Ca- and Sr-analogs, has recently been projected as potential electronic ceramic material (thermally stable capacitor, chemical sensor for humidity, CO and NO_x, etc.). In order to fill the information gaps in the reported research, a vigorous and systematic investigation on these exotic materials has been initiated. A thorough study of BaSnO₃ with respect to its synthesis, processing and microstructural characterization has been made. In order to establish a standard methodology for low-cost mass-manufacturing with identical and beneficial microstructure and reproducible electrical characteristics, different synthesis routes (solid-state and self-heat-sustained) were adopted. Evolution of microstructure which is intimately related to the envisaged properties in the ceramics, was closely and systematically followed in terms of sintering over a wide range of temperatures and soak time. This communication forms the first of two parts in a series of investigations on MSnO₃ systems, where results on the synthesis and processing of “phase pure” barium stannate (BaSnO₃) and development of interesting microstructure are presented.     

Composition dependence of structure and optical properties of Cu2ZnSn(S,Se)4 solid solutions: An experimental study

The evolution of structure and optical properties of Cu₂ZnSn (S_xSe_1−x)₄ (CZTSSe) solid solutions in a wide composition range (0 ≤ x ≤ 1) has not been fully elucidated. We have performed comprehensive characterization on the CZTSSe powders with different S/Se ratios, which were synthesized by the solid state reaction method. X-ray diffraction patterns demonstrate that the lattice parameters a and c of CZTSSe decrease lineally when S replace Se gradually, which obeys the Vegard's rule. The A₁ Raman modes of CZTSSe show a typical two-mode behavior. The absorption spectra reveal that the band gap of CZTSSe can be tuned monotonously between 0.96 and 1.5 eV with almost linearity, and a small band gap bowing constant (b ≈ 0.08 eV) is deduced.