Thermodynamic quantities and oxygen nonstoichiometry of undoped BaTiO 3− δ by thermogravimetric analysis

Abstract

Thermogravimetry analysis was performed to determine the oxygen nonstoichiometry of oxides by using a home-made experimental set-up with Cahn D200 microbalance for an undoped BaTiO 3− δ specimen. The relative partial molar enthalpy and entropy of oxygen for undoped BaTiO 3− δ were also calculated from the slope and intercept of the δ − P O 2 − T relation, respectively. The negative signs of partial molar enthalpy and entropy in the oxygen deficient regime indicated that the incorporation of oxygen is an exothermic process. The values for K i and K Re of the undoped BaTiO 3− δ are best described by the following equations: K i / cm − 6 = ( 1.69 ± 1.51 ) × 10 46 exp − 2.93 ± 0.23 eV k T K Re / cm − 9 = ( 7.15 ± 5.55 ) × 10 73 exp − 5.80 ± 0.15 eV k T The difference in n– p transition P O 2 compared with reference should be further understood by identifying the cation nonstoichiometry and the value of impurity defects for the clarification of defect structure.