Effect of CuO on the Sintering Temperature and Piezoelectric Properties of (Na _0.5 K _0.5 )NbO ₃ Lead‐Free Piezoelectric Ceramics

Abstract

When a small amount of CuO was added to (Na 0.5 K 0.5 )NbO 3 (NKN) ceramics sintered at 960°C for 2 h, a dense microstructure with increased grains was developed, probably due to liquid‐phase sintering. The Curie temperature slightly increased when CuO exceeded 1.5 mol%. The Cu 2+ ion was considered to have replaced the Nb 5+ ion and acted as a hardener, which increased the E c and Q m values of the NKN ceramics. High piezoelectric properties of k p =0.37, Q m =844, and ɛ 3 T /ɛ 0 =229 were obtained from the specimen containing 1.5 mol% of CuO sintered at 960°C for 2 h.