Electrophysical Properties of Bismuth Titanates with the Pyrochlore Structure Bi_1.6M_xTi₂O_{7 – δ} (М = In, Li)¹

Abstract—Lithium-containing bismuth titanates with the pyrochlore-type structure Bi_1.6Li_xTi₂O_{7 – δ} were obtained for the first time. The formation of the pyrochlore phase was confirmed by X-ray diffraction analysis, scanning electron microscopy and local microanalysis. In Bi_1.6M_xTi₂O_{7 – δ}, the lithium and indium are occupied the bismuth sites, primarily. The electrophysical properties of doped bismuth titanates were studied by impedance spectroscopy in the frequency range 1–10⁶ Hz. In the low-temperature range (of up to ~400°C), electron conductivity predominates; above 400°C, the oxygen-ion type of conductivity is revealed. In the range p(O₂) = 0.21–1 atm, the average value of the sum of ion transport numbers is 0.5 at 500–550°C. The relaxation process was found from the frequency dependences of the dielectric parameters (ε', tan δ, M ''), which was of the same type for systems with different dopants (In, Li) probably due to the hopping mechanism of oxygen conductivity.