Microstructural, structural, dielectric and piezoelectric properties of potassium sodium niobate thick films

The effects of processing parameters, particularly powder packing and sintering temperature, on the microstructural and structural properties of potassium sodium niobate (K0.5Na0.5NbO3 or KNN) thick films were investigated. The KNN thick films were prepared by adding 1 mass% of potassium sodium germanate (KNG), which served as a liquid-phase sintering aid. The sintered films had preferred crystallographic orientations along [100]pc and [10-1]pc, the origin of which lay in the compressive stresses developed during cooling as a result of the thermal expansion mismatch between the film and the substrate. In addition, the dielectric permittivity, dielectric loss and piezoelectric d33 coefficient of the obtained films were compared with those of KNN bulk ceramics.