Microstructure evolution and electromechanical properties of (K,Na) NbO3‐based thick films

Abstract

ABSTRACTThis study investigated an unconventional method of electrophoretic deposition (EPD) for the processing of environmentally benign (K0.5Na0.5)0.99Sr0.005NbO3 (KNNSr) thick films on Pt/alumina substrate. EPD allows rapid, economical, and low‐waste processing of thick films and thus offers an integration advantage for electronics manufacturing. To understand the functional response of the KNNSr thick films, the effect of the sintering temperature and atmosphere on their structure, microstructure, and electromechanical properties was investigated. KNNSr thick films densify in constrained conditions in a very narrow temperature range only a few 10°C below the melting temperature of 1140°C. Up to 1100°C the relative density increases to 80%, upon further heating to 1110°C we observed only the grain growth and pore coalescence. The densification is not affected significantly by the atmosphere. The local domain structure of 25‐33 μm thick KNNSr films was similar, while the dielectric and electromechanical properties increased with the increasing sintering temperature. KNNSr thick film sintered at 1100°C has a thickness‐coupling factor kt of 0.4, comparable to that of bulk. The results reveal that the EPD enables the economic processing of high‐performance thick films on complex‐shape substrates that are difficult to fabricate using conventional thick‐film methods.