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

Abstract

The magnetic susceptibility χ(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 ρ(T) at 4.2 K < T < 293 K are studied for samples of perovskite-phase KTaO3 obtained by both solid-phase synthesis (KTaO 3 s ) and deposition on a cathode during electrolysis of melts (KTaO 3 e ). Yellowish white KTaO 3 s powders are diamagnetic and reveal dielectric properties. Dark polycrystalline KTaO 3 e samples with metallic luster are characterized by the dependence ρ(T) typical of metals and additional paramagnetic contribution to the paramagnetic susceptibility as compared with KTaO 3 e . Changes in the properties of KTaO3 during electrocrystallization are attributed to partial reduction of tantalum. They are revealed in the structural features of KTaO 3 e (excess of tantalum as compared to the stoichiometric composition of KTaO 3 e , 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.