Synthesis and Characterization of (K_0.5Na_0.5)NbO₃Piezoelectric Ceramics Prepared Using K_5.70Li_4.07Nb_10.23O₃₀as a New Sintering Aid

Abstract

K 0.5 Na 0.5 NbO 3 (KNN) lead-free piezoelectric ceramics containing 1 mol% ZnO (KNNZ) were prepared by optimizing the sintering conditions using the newly developed K 5.70 Li 4.07 Nb 10.23 O 30 (KLN) as a sintering aid. The phase structure and electrical properties of the KNNZ ceramics were investigated as a function of the KLN concentration. The results show that a small amount of KLN was incorporated into the lattice and formed a single-phase perovskite structure. The KLN modification lowered the phase transition temperature of the orthorhombic-tetragonal structure and increased the Curie temperature. Interestingly, an appropriate amount of KLN can simultaneously improve the sinterability of the KNNZ ceramics and the ferroelectric and piezoelectric properties. Good piezoelectric and dielectric properties (piezoelectric constant, d 33 = 131 pC/N; planar coupling coefficient, k p = 0.42; dielectric constant, ε r = 634; and mechanical quality factor, Q m = 20) were obtained for the KNNZ ceramics doped with 1 mol% KLN. Therefore, KNNZ + 1.0 mol% KLN ceramics containing an appropriate amount of KLN are good candidate materials for the preparation of lead-free piezoelectric ceramics.