Ceramics-Silikáty 55, (2) 101 - 105 (2011)

New lead-free piezoelectric ceramics (1-x)(Na_0.5K_0.5)NbO_3–xBa(Ti_0.95Hf_0.05)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, k_p = 0.38, ε₃₃^T = 1690, Q_m = 108 and T_c = 267 °C, compared to pure NKN.