Interfacial layer effects in Ba_1-xSr_xTiO₃ thick films prepared by plasma spray

The dielectric properties of high k dielectric thick films prepared by thermal spray were investigated. BaTiO₃ and Ba_0.68Sr_0.32TiO₃ thick films were deposited using plasma spray on Ag·Pd screen-printed alumina substrates. The sprayed films were predominantly polycrystalline but contained an amorphous second phase. The dielectric constants of the films decreased with decreasing film thickness in 10 ∼ 60 μm range. This was attributed to the presence of an interfacial layer between the film and the substrate as determined by capacitance measurements. The capacitance density of the interfacial layer was determined to be ∼ 2.7 nF/cm². The capacitance density of the interfacial layer increased to 12 nF/cm² after post heat treatment at 500°C for 20 hours.