phase transition and electrical properties of new lead-free (na0.5k0.5)nbo3–ba(ti0.95hf0.05)o3 solid solution ceramics

New lead-free piezoelectric ceramics (1-x)(Na0.5K0.5)NbO3–xBa(Ti0.95Hf0.05)O3 (NKN-xBTH) doped with 0.8 mol.% CuO have been successfully fabricated by traditional solid state sintering. Owing to complex atomic occupation at A-sites and B-sites, the ferroelectric phase transition of NKN becomes more and more diffuse with increasing BTH content. On the other hand, it was found that the addition of a small amount of BTH shifts an orthorhombic-tetragonal polymorphic phase transformation of pure NKN composition downwards to room temperature. The two-phase transition zone was identified approximately at 0.04 < x < 0.06 and the ceramic with x = 0.06 possesses obviously enhanced electrical properties: d33 = 185 pC/N, kp = 0.38, ε33 T = 1690, Qm = 108 and Tc = 267 °C, compared to pure NKN.