THE STUDY OF THE ION TYPE IS RESPONSIBLE FOR THE TRANSFER TO Na3DyV2O8

As a result of studying the type of ion responsible for the transfer by the Tubandt method, unipolar transfer of sodium Na+ ions in Na3DyV2O8 double vanadate was established. The ionic transfer numbers were ti ~ 1

ELECTRIC TRANSFER IN DOUBLE VANADAT YTTERBIA

Double vanadate Na3Yb(VO4)2 was synthesized and the effect of temperature on electrical conductivity, thermal expansion, and phase transformations was studied.В работе синтезирован двойной ванадат Na3Yb(VO4)2, изучено влияние температуры на электропроводность, термическое расширение и фазовые превращения

New Li-Mg phosphates with 3D framework : experimental and ab initio calculations

Two new lithium-magnesium phosphates LiMg6(PO4)3(P2O7) and Li(Mg5.62Sc0.19Li0.19)(PO4)3(P2O7) were synthesized by the solid-phase method. Using high-resolution time-of-flight neutron powder diffraction (TOF NPD) and X-ray powder diffraction (XRPD), we established that these phosphates have Pnma orthorhombic structure with the cell parameters a=9.14664(5) Å, b=18.83773(8) Å, c=8.27450(4) Å, V=1425.71(1) Å3 and a=9.14516(5) Å, b=18.84222(9) Å, c= 8.28204(4) Å, V=1427.12(1) Å3, respectively. The crystal structures can be described by stacking of the [Mg6O18]∞ or [Mg5.62Sc0.19Li0.19O18]∞ wavy layers, which are parallel to the (100) direction and interconnected through PO4 tetrahedra and P2O7 groups to a 3D-framework. Li atoms are located in large tunnels formed in a 3D lattice, which contributes to lithium diffusion. AC impedance spectroscopy shows that LiMg6(PO4)3(P2O7) and Li(Mg5.62Sc0.19Li0.19)(PO4)3(P2O7) have Li ion conductivity of 3.6 10-4 S/cm and 1.7 10-4 S/cm at 950 °C, with activation energy of 1.28 eV and 1.55 eV, respectively. NMR MAS studies confirmed a coexistence of pyro- and orthogroups in the structure of both phases and two lithium positions in Li(Mg5.62Sc0.19Li0.19)(PO4)3(P2O7). The first- principles method was used to study the electronic structure and stability of the two phases. The calculated formation enthalpies demonstrated that Sc is a stabilizing impurity in LiMg6(PO4)3(P2O7), while there exists a strong destabilization of olivine LiMgPO4 upon doping with Sc. This explains the failure to synthesize the Sc-doped olivine. The new phosphate LiMg6(PO4)3(P2O7) is a dielectric with band gap of 5.35 eV, which decreases to 4.85 eV due to a localized Sc 3d peak upon doping with Sc. These findings are consistent with the results obtained from UV-Vis spectroscopy. The new phase may be a good optical matrix similar to LiMgPO4

Diffusion of barium ions in the Ba3-3xLa2x?x(VO4)2 solid solution

Diffusion coefficients for 133Ba, 90Sr, and 45Ca radionuclides in the solid solution Ba3-3xLa2x?x(VO4)2 (x = 0, 0.05, 0.1, 0.15) are measured in the temperature range 800 to 1000°C using the layer-by-layer radiometric analysis. It is established that Dca* ? DSr? > DBa*. Increasing the concentration of vacancies ? in the barium sublattice leads to an increase in the diffusion coefficients of the alkaline-earth metal cations. The activation energies for the radionuclide diffusion are determined; their values (?1.1 eV) are close to the activation energy for ionic conduction. Cations M2+ are shown to migrate via the positions of Ba(2). © 1999 MAHK "Hayka/Interperiodica Publishing"