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: d
₃₃
=231 pC/N, k
_P
=41.0%, k
_t
=50.5%, P
_r
=40.2 muC/cm
²
, 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 (d
₃₃
=164 pC/N, k
_p
=36.3%, k
_t
=48.6%) and strong ferroelectricity (P
_r
=38.8 mu C/cm
²
, 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.