Lead-free piezoelectric single crystals with nominal composition of 99.3K0.5Na0.5NbO3-0.4LiBiO3-0.3CaZrO3(KNN-LB-CZ) doped with MnO2 were prepared by a seed-free, solid-state crystal growth method. The effects of MnO2 content on the growth, structure and piezoelectric properties of KNN-LB-CZ single crystals were investigated.The results show that the addition of MnO2 inhibits the crystal growth at different growth temperatures. When the MnO2 content is in the range of 0.125%~0.5%, the single crystal area on the upper surface of the sample decreases from 95% to 30% gradually, and when the MnO2 content is over 0.625%, there is almost no large grains visible to the human eye.The addition of MnO2 does not change the perovskite structure of the crystals or produce second phase in the crystal, but it is beneficial to the densification of the single crystal microstructure.An appropriate amount of MnO2 doping is beneficial to improve the piezoelectric properties of single crystal. The piezoelectric constant d33 and dielectric loss tan δ of single crystal without MnO2 doping are 200 pC/N and 0.06, respectively. When the MnO2 doping contend is 0.5%, the d33 of the single crystal increases to 450 pC/N, and its dielectric loss also decreases to 0.03.

piezoelectric materials；sodium potassium niobate；single crystal; seed-free solid-state growth；piezoelectric property