Processing of piezoelectric (Li,Na,K)NbO3 porous ceramics and (Li,Na,K)NbO3/KNbO3 composites

Porous Li-0.06(Na0.5K0.5)(0.94)NbO3 (LNKN-6) ceramics with different pore volumes have been prepared using preceramic powder and phenol resin fiber (Kynol (TM)) as a pore former. It was confirmed that the porous ceramics synthesized by the "two-stage firing method" suppressed the loss of alkali elements from the porous body during heat treatment. The porous LNKN-6 ceramics were then converted to LNKN-6/KNbO3 Composites through soaking and heat treatment using a sol-gel precursor source composed of KNbO3 to form 3-3-type composites. The microstructure, dielectric, and piezoelectric properties of the porous LNKN-6 ceramics and LNKN-6/KNbO3 Composites were characterized and compared. The LNKN-6/KNbO3 composites had a hollow structure whose pores in the region near the surface were filled and coated with KNbO3 precipitates; however, a large amount of residual air was trapped in the pores inside the composites. As a result, the LNKN-6/KNbO3 composites fabricated using 30 vol % Kynol (TM) Showed an enhanced piezoelectric voltage output coefficient (g(33)) of 63.0 x 10(-3) V.m/N, compared with monolithic LNKN-6 ceramics having a g(33) of 30.2 x 10(-3) V.m/N.