Microstructure and Piezoelectric Properties of (Na0.5K0.5)NbO3 Lead-Free Piezoelectric Ceramics with V2O5 Addition

Abstract

Various amounts of Nb2O5 in the (Na0.5K0.5)NbO3 (NKN) ceramic were replaced by V2O5 to decrease its sintering temperature to below 950 degrees C. A small V2O5 content resulted in a dense microstructure with an increased grain size for the specimen sintered at 900 degrees C due to the presence of a liquid phase. When V2O5 was added to the NKN ceramics, their orthorhombic-to-tetragonal transition temperature increased from 178 degrees C to around 200 degrees C. However, their Curie temperature decreased from 402 degrees C to around 330 degrees C. The k(p), epsilon(T)(3)/epsilon(0), and Q(m) values increased with V2O5 addition, probably due to the increased density and poling state, which was identified by the phase angle. The specimen with x = 0.05, sintered at 900 degrees C for 8 h, exhibited the following piezoelectric properties: k(p) = 0.32, epsilon(T)(3)/epsilon(0) = 245, d(33) = 120 (pC/N), and Q(m) = 232.