Dielectric properties of plasma-spray-deposited BaTiO₃ and Ba_0.68Sr_0.32TiO₃ thick films

The dielectric properties of high-k dielectric BaTiO₃ and Ba_0.68ST_0.32TiO₃ thick films deposited on alumina substrates using a plasma-spray process were investigated. The as-deposited films were predominantly crystalline but contained an amorphous second phase, the amount of which depended on spray conditions. The effect of the spray conditions on crystallinity was studied and related to the dielectric properties of the films. The presence of a low dielectric constant interfacial layer in plasma-spray-deposited films was determined from the dependence of the dielectric constant on film thickness. After annealing at 500 °C for 20 h in air, the crystallinity and dielectric constant increased. Annealing was also found to affect the interfacial layer properties.