Cu-particle-dispersed (K0.5Na0.5)NbO3 composite thin films derived from sol–gel processing

Abstract

Sol–gel processing of Cu-particle-dispersed (K0.5Na0.5)NbO3 (Cu/KNN) thin films was studied in an attempt to develop a method producing piezoelectric composite films with good mechanical performance. The Cu/KNN films were prepared via crystallization annealing at 650–750 °C for 1 min in air, followed by reduction annealing at 400–500 °C for 1–2 h in a 5% H2 and 95% Ar gas mixture. The resultant composite films consisted of perovskite KNN, metallic Cu, and Cu4O3. This suggests that the decomposition of Cu sources takes two different ways in this study. The Cu/KNN composite films containing Cu4O3 phases were produced by the crystallization annealing at 700 °C for 1 min followed by the reduction annealing at 500 °C for 1 h. Surface morphology observations reveal that these films have dense KNN matrix with a grain size of ~200 nm and uniformly dispersed Cu or Cu4O3 particles with a size of <500 nm.