Dielectric properties of spray deposited BaTiO₃ and Ba_0.68Sr_0.32TiO₃

The microstructure and dielectric properties of BaTiO₃ and Ba_0.68Sr_0.32TiO₃ thick films deposited by thermal spray were investigated. The as-deposited films were predominantly crystalline with a small amount of an amorphous second phase. The as-deposited BaTiO₃ films had dielectric constants as high as 240 at room temperature. Upon annealing in air at 500°C, the dielectric constant increased to 480. This increase in dielectric constant was attributed, in part, to the crystallization of the amorphous second phase. The stabilized phase depended on the spray process used. The high velocity oxy fuel (HVOF) spray process resulted in the deposition of paraelectric BaTiO₃, whereas the plasma spray process resulted in the ferroelectric phase.