Electrochemical Properties of Bi4Ti3-xCrxO12-0.5x (0.4 ≤ x ≤ 1.2) Solid Solutions with a Layered Perovskite Structure

Chromium-containing bismuth titanates Bi4Ti3-xCrxO12-delta (0 <= x <= 1.2) with a layered perovskite structure and with the number of layers in the perovskite-like unit m = 3 at x <= 0.5 and m = 4 at 0.5 < x <= 1.2 were synthesized by the solid state method. The electrochemical properties of Bi4Ti1.8Cr1.2O11.38 (m = 4) and Bi4Ti2.6Cr0.4O11.8 (m = 3) were studied by impedance spectroscopy and DC electric conductivity measurements in different gas media. The oxygen conductivity increased at temperatures (t) of 450-500 degrees C. For the samples with m = 4 at t >= 500 degrees C in the frequency range of the order of a few Hz, the imaginary part of impedance was inverted, which was explained by the electrochemical process on electrodes. At t >= 600 degrees. a reversible breakdown of the Bi4Ti2.6Cr0.4O11.8 sample in an electric field of over 30 V/m was observed. It was concluded that the conductivity of Bi4Ti3-xCrxO12-delta is of electron-ion type.