Specific features of the crystal structure and magnetic properties of KTaO3 produced by electrolysis of melts

The magnetic susceptibility chi(T) at 4.2 K < T < 293 K; the dependence of the magnetic moment on the magnetic field strength, M(H), at 4.2, 77, and 293 K; and the electrical resistivity rho(T) at 4.2 K < T < 293 K are studied for samples of perovskite-phase KTaO3 obtained by both solid-phase synthesis (KTaO3s) and deposition on a cathode during electrolysis of melts (KTaO3e). Yellowish white KTaO3s powders are diamagnetic 3 3 and reveal dielectric properties. Dark polycrystalline KTaO3e samples with metallic luster are characterized by 3 the dependence rho(T) typical of metals and additional paramagnetic contribution to the paramagnetic susceptibility as compared with KTaO3e. Changes in the properties of KTaO3 during electrocrystallization are attributed to partial reduction of tantalum. They are revealed in the structural features of KTaO3e (excess of tantalum as compared to the stoichiometric composition of KTaO3e, deficiency of the oxygen sublattice, and clearly pronounced anharmonicity of atomic vibrations). A change of the cation-anion-cation interactions, occurring owing to the overlapping of oxygen p orbitals with tantalum t(2g) orbitals and the formation of impurity levels near the conduction band, leads to the generation of free carriers, which make a paramagnetic contribution to the magnetic susceptibility. (C) 2005 Pleiades Publishing, Inc.