Non-stoichiometric disorder in La 2Ti 2O 7 at elevated temperatures

Abstract

The defect structure of polycrystalline La 2Ti 2O 7 was investigated by measuring the oxygen partial pressure (10 0− 10 −21 atm) dependence of equilibrium electrical conductivity in the temperature range 850–1050°C. The observed data were proportional to P O 2 −1 4 for P O 2 < 10 −8atmand proportional to P O 2 +1 4 for P O 2 > 10 −4atm. The region of linearity where the electrical conductivity varies as P O 2 −1 4 increased as the temperature was decreased. The observed data are consistent with the presence of accidental acceptor impurities in the sample. The average values of the activation enthalpies for electrical conduction are 106.40 kcal mol −1 (4.62 eV) and 42.42 kcal mol −1 (1.84 eV) respectively in the n-type and p-type regions of electrical conductivity.