The phase diagrams of binary systems of gallium sulfate with lithium or sodium sulfate were studied for the first time. The Li2SO4–Ga2(SO4)3 system is of the eutectic type. The coordinates of the eutectic are (548°C, 30 mol % Ga2(SO4)3). The region of a solid solution based on the high-temperature modification α-Li2SO4 is small. In the Na2SO4–Ga2(SO4)3 system, compound Na3Ga(SO4)3 forms, which melts incongruently at 585°C. The coordinates of the eutectic are (538°C, 17 mol % Ga2(SO4)3). The region of a solid solution based on α-Na2SO4 reaches 8 ± 1 mol % Ga2(SO4)3. The X-ray powder diffraction pattern of Na3Ga(SO4)3 was indexed in a tetragonal unit cell with the parameters a = 9.451(3) Å and c = 7.097(3) Å; the unit cell parameters for an aluminum-containing analog, Na3Al(SO4)3, are a = 9.424(5) Å and c = 7.053(3) Å.
The thermomechanical and electrical conductivity properties of praseodymium molybdate Pr5Mo3O16 + δ prepared by a solid-phase method were studied. The electrical conductivity of praseodymium molybdate samples measured at temperatures in the range 373–1173 K with the oxygen partial pressure in the gas of 10–3 to 0.21 atm was found to increase from ~10–7 to ~10–2 S/cm and to be almost independent of oxygen pressure. It is for the first time that electrical conductivity a reductive atmosphere (Ar/H2 5%) was found to increase from 0.1 to 1.2 S/cm in the same temperature range. Studies of the chemical stability of Pr5Mo3O16 + δ with respect to solid electrolytes showed the absence of chemical reactions with GDC at 1273 K and with YSZ at 1223 K. The combination of these properties evidences for the potential of praseodymium molybdate for use as an anode material for solid oxide fuel cells (SOFCs).
New complex oxides of composition Pr1 – yCayFe0.5 + x(Mg0.25Mo0.25)0.5 – xO3, 0.0 ≤ x ≤ 0.1, 0.42 ≤ y ≤ 0.8 having an orthorhombically distorted perovskite structure have been prepared. The thermal expansion and electric conductivity of the new phases have been studied in the temperature range between 100–900oC. The results of our study imply that thin films of the oxides studied can be treated as electrode materials for symmetric solid-oxide fuel cells.
The properties of hybrid materials based on the MK-40 heterogeneous membrane, the MF-4SK homogeneous membrane, and zirconium oxide with a functionalized surface are studied. The ionic conductivity and diffusion parameters of these materials were studied. The presence of the asymmetry effect of diffusion permeability and mutual diffusion of HCl and NaCl solutions through the studied membranes was revealed. The causes of asymmetry and the mechanisms of the influence of the dopant on diffusion parameters are considered.
Yetnonsynthesized compounds of the compositions A2BHal5, A3BHal6, and ABHal4 in systems of mono and trivalent metal halides were predicted, and so was the type of their crystal structure under nor mal conditions. The calculations were performed by precedentbased pattern recognition methods using a special system for computer design of inorganic compounds. The new compounds were predicted using only the data on the properties of elements and simple halides.
Arsenates A0.5Zr2(AsO4)3 (A = Mg, Ca, Sr, Ba), synthesized through sol–gel route with subsequent heat treatment, have been studied by X-ray diffraction, electron probe microanalysis, and IR spectroscopy. Mg0.5Zr2(AsO4)3 crystallizes in the Sc2(WO4)3 structure type (space group P21/n). A0.5Zr2(AsO4)3 (A = Ca, Sr, Ba) crystallize in the NaZr2(PO4)3 structure type (space group R ). The Ca0.5Zr2(AsO4)3 and Ba0.5Zr2(AsO4)3 structures have been refined by the full-profile analysis. The structure frameworks are composed of ZrO6 octahedra and AsO4 tetrahedra. The alkaline earth metal atoms occupy one of the two extraframework positions inside the structure columns. The internal vibrational frequencies of the tetrahedron have been assigned. The number of the observed bands corresponds to the number predicted by the factor group analysis of vibrations for space groups R and P21/n.