Composition induced rhombohedral-tetragonal phase boundary in BaZrO_3 modified (K_(0.445)Na_(0.50)Li_(0.055))NbO_3 lead-free ceramics

摘要

(1-x)(K_(0.445)Na_(0.50)Li_(0.055))NbO_3-xBaZrO_3 (KNNL-xBZ) lead-free piezoelectric ceramics were fabricated by the traditional sintering process. The effect of BaZrO_3 on the phase structure, microstructure, and electrical properties were investigated. The XRD patterns confirm that BaZrO_3 entirely diffused into (K_(0.445)Na_(0.50)Li_(0.055))NbO_3 lattice to form new solid solutions, leading to a coexistence of rhombohedral and tetragonal phases with x=0.08. Enhanced electrical properties of d_(33)=317 pC/N, k_p=42.9%, ε_r=2600, and tan δ=0.03 were obtained with x=0.08 due to the rhombohedral-tetragonal phase boundary near room temperature with a dense microstructure. These results may provide the possibility on improving the piezoelectric properties of KNN-based ceramics by constructing the coexistence of rhombohedral and tetragonal phases.