Electrophoretic deposition and properties of strontium-doped sodium potassium niobate thick films

We have processed strontium-modified potassium sodium niobate (KNNSr) piezoelectric thick films on metalized alumina by electrophoretic deposition and sintering for energy-harvesting applications. The deposition yield, the electric field in the close vicinity of the planar working electrode (calculated with a finite-element method) and the thickness profiles of the as-deposited layers were examined for ethanol-based suspensions with different conductivities, deposition times, inter-electrode distances and sizes of the counter electrode. Uniformly thick and defect-free, as-deposited KNNSr layers were processed from a suspension with a conductivity of 21.2 μS/cm, deposited for 90 s, for an inter-electrode distance of 3 mm and a diameter of the counter electrode similar to the sample's dimensions. KNNSr layers sintered at 1100 °C with a thickness of 30 μm and a relative density of 75% exhibited a dielectric permittivity of 325, dielectric losses of 0.04 at 10 kHz and room temperature, and a d33 coefficient of 60 pC/N.