Ca~(2+) doping effects in (K, Na, Li)(Nb_(0.8)Ta_(0.2))O_3 lead-free piezoelectric ceramics

摘要

Lead-free (K0.5-x/2Na0.5-x/2Lix)(Nb0.8Ta0.2)O-3 (KNLNT) and (K0.49-x/2Na0.49-x/2-LixCa0.01)(Nb0.8Ta0.2)O-3 (KNLNT-Ca) ceramics were prepared by a conventional ceramic processing. Structural analysis shows that the Ca2+ doping takes the A site of ABO(3) perovskite and decreases the phase transition temperature. Property measurements reveal that as a donor dopant, the Ca2+ doping results in higher room-temperature dielectric constant, lower dielectric loss, and lower mechanical quality factor. In addition, the Ca2+ doping does not change the positive piezoelectric coefficient d(33), but increases the converse piezoelectric coefficient d33* significantly. This is likely due to the increase in the relaxation, as well as the appearance of (Ca-Na/K center dot-V-Na/K') defect dipoles.