Fabrication and piezoelectric properties of (K 0.5 Na 0.5 )NbO 3 -based ceramics doped with Bi-perovskites

The effect of the addition of Bi-perovskites to (Li 0.04 K 0.52 Na 0.44 )(Nb 0.84 Ta 0.1 Sb 0.06 )O 3 (LF4) ceramics was studied to improve the properties of lead-free piezoelectrics. Ceramics with the relative density above 96% were successfully obtained by a solid state reaction process. The changes in lattice parameters indicated that the vacancy concentration at the A-site of the perovskite structure and the tetragonality of the crystal lattice were reduced with the addition of BiFeO 3 . The addition of BiFeO 3 changed the LF4 to a soft-piezoelectric. The electrical insulation of the LF4 was improved with the addition of BiFeO 3 , which made a full poling possible under high electric fields. A few mol% of BiFeO 3 was effective to improve the remanent polarization of the LF4 ceramics and a piezoelectric d 33 constant of about 358 pm/V was obtained in the 0.4 mol% doped ceramics.