Bi0.5(Nal-x-yKxLiy)0.5TiO3 Lead-free Piezoelectric Ceramics and Their Applications for Buzzers and Filters

The new system of (BNKLT-x/y) lead-free piezoelectric ceramics, which were prepared by using conventional oxide mixing processing, were invented in our group. The ceramics show excellent piezoelectric and ferroelectric properties: d₃₃=231 pC/N, k_P=41.0%, k_t=50.5%, P_r=40.2 muC/cm², and E_c=2.47 kV/mm, respectively. The dependence of P-E loops on temperature reveals that the depolarization temperature T_d of BNKLT-0.15/0.075 ceramics, which simultaneously have good piezoelectric properties (d₃₃=164 pC/N, k_p=36.3%, k_t=48.6%) and strong ferroelectricity (P_r=38.8 mu C/cm², E_c=3.73 kV/mm) at room temperature, is about 195degC. The ceramics were used for making buzzers by ordinary techniques as used for PZT-based buzzers, and the measurement of the electric-acoustic properties shows that the buzzers possess a very high sound pressure (~90 dB). The ceramics invented were also used for making middle frequency piezoelectric ceramic filters.