Study of oxygen diffusion in dense lanthanum oxide ceramics

Abstract

A direct oxygen diffusion study using isotopes in dense La₂O₃ ceramics fabricated with the addition of Sr and Ge oxides was performed by secondary-ion mass spectrometry. The experiments using the ¹⁸O isotope were carried out in the temperature range 400–700 °C for 1 h. The surface concentration of ¹⁸O was found to depend on the annealing temperature. The temperature dependence of oxygen diffusion was determined to be expressed as D^*(cm²/s) = (8.9 × 10⁻³)exp(−128.8[kJ/mol]/RT), where D^* is the diffusion coefficient, R is the gas constant, and T is temperature. On the basis of a comparison with the results of oxygen diffusion studies of CeO₂ and LaGaO₃, we concluded that oxygen diffusion in La₂O₃ occurs via a vacancy mechanism.