Phase composition and electrical properties of manganese-containing bismuth titanates

Manganese-containing bismuth titanate solid solutions were obtained by the ceramic technique over a wide range of compositions. It was found by means of electron microscopy and elemental analysis that the main phase in all samples is a pyrochlore. Inclusions of MnO2, layered perovskite structure Bi4Mn0.4Ti2.6O13 and unknown compounds BiMn1.1Ti0.7O5.6 were detected in samples with a high content of mangane. Single-phase samples with pyrochlore structure are formed at low concentrations of manganese. All samples have considerable porosity. The method of impedance spectroscopy shows that all samples are the electron - ionic conductors. At increasing of Mn content the conductivity of the samples grows, conductivity activation energy decreases. Samples hodograph impedance with a minimum content of Mn at temperatures above 460o C and frequency of about 10 kHz demonstrates unusual behavior. In particular, the imaginary part of the impedance within one decade of frequency goes to the lower half of the complex plane. The inversion of the imaginary part of the impedance is explained by ionization of gas in the pores.