Cation Interdiffusion in Polycrystalline Calcium and Strontium Titanate

Abstract

A method has been developed to study bulk lattice interdiffusion between calcium and strontium titanate by fabrication of a diffusion couple using cosintering. The measured interdiffusion coefficients, D̃ ( C ), indicate that strontium impurity diffusion in calcium titanate occurs at a faster rate than calcium impurity diffusion in strontium titanate. These interdiffusion coefficients are composition independent when the concentration of the calcium cation exceeds that of the strontium cation; otherwise D̃( C ) is strongly composition dependent. Investigations into the effect of cation nonstoichiometry give results that are consistent with a defect incorporation reaction in which excess TiO 2 , within the solid solubility limit, produces A‐site cation vacancies as compensating defects. The interdiffusion coefficients increase with increasing concentrations of TiO 2 , so it is concluded that interdiffusion of these alkaline‐earth cations in their titanates occurs via a vacancy mechanism.