Thermodynamic quantities and oxygen nonstoichiometry of undoped BaTiO3−δ by thermogravimetric analysis

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 BaTiO3−δ specimen. The relative partial molar enthalpy and entropy of oxygen for undoped BaTiO3−δ were also calculated from the slope and intercept of the δ−PO2−Tδ−PO2−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 Ki and KRe of the undoped BaTiO3−δ are best described by the following equations:Ki/cm−6=(1.69±1.51)×1046 exp−2.93±0.23 eVkTKRe/cm−9=(7.15±5.55)×1073 exp−5.80±0.15 eVkTThe difference in n–p   transition PO2PO2 compared with reference should be further understood by identifying the cation nonstoichiometry and the value of impurity defects for the clarification of defect structure.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Oxygen nonstoichiometry for an undoped BaTiO3−δ using thermogravimetry analysis.► Defect chemical analysis based on acceptor impurity. ► The relative partial molar enthalpy and entropy of oxygen for undoped BaTiO3−δ were calculated.