Fabrication and Properties of Middle Frequency Filters by Using [Bi0.5 (Na1-x-yKxLiy)0.5]TiO3 Lead-free Piezoelectric Ceramics

[Bi-0.5(Na1-x-yKxLiy)(0.5)]TiO3 (BNKLT) lead-free piezoelectric ceramics invented in authors' group were used for making of two kinds of middle frequency ceramic filters. The BNKLT ceramics was fabricated into the single disc for middle frequency filter with the center frequency being about 530 kHz by using the skeletal vibration mode. The loss insertion is about 3 dB, and the bandwidth is about 8.8 kHz. It was obtained that the filter has sharp upper and lower cut off frequencies. The BNKLT ceramics was also fabricated into the multi-section ladder for pass-band filter with the center frequency about 460 kHz by using the full electrode radial vibration mode of the resonance samples. The band -pass filter also has sharp upper and lower cut off frequencies with the curve smooth, and the loss insertion less than 6 dB and the out-band attenuation more than 30 dB.