Lead-free (K0.5-x/2Na0.5-x/2Lix)(Nb0.8Ta0.2)O3 (KNLNT) and (K0.49-x/2Na0.49-x/2-LixCa0.01)(Nb0.8Ta0.2)O3 (KNLNT-Ca) ceramics were prepared by a conventional ceramic processing.Structural analysis shows that the Ca2+ doping takes the A site of ABO3 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 d33,but increases the converse piezoelectric coefficient d33 significantly.This is likely due to the increase in the relaxation,as well as the appearance of (CaNa/K°-VNa/K″) defect dipoles.