Low temperature sintering of lead-free Bi0.5(Na0.82K0.18)0.5TiO3 piezoelectric ceramics by co-doping with CuO and Nb2O5

Effect of excess CuO additive on the sintering behavior and piezoelectric properties of Bi0.5(Na82K0.18)0.5TiO3 ceramics was investigated. The addition of small amount of excess CuO as low as 1 mol% was quite effective to lower the sintering temperature (Ts) of BNKT ceramics down to 975 °C while their piezoelectric properties were degraded by Cu doping. However, the electric field-induced strain was markedly enhanced by further addition of Nb2O5 with CuO without elevating Ts. The normalized strain Smax/Emax of 427 pm/V was obtained with a specimen sintered with 0.02 mol CuO and 0.03 mol Nb2O5 in excess.