Composition induced rhombohedral–tetragonal phase boundary in BaZrO3 modified (K0.445Na0.50Li0.055)NbO3 lead-free ceramics

• XRD indicates the coexistence of rhombohedral and tetragonal phases in 0.07≤x≤0.08.
• Dense microstructure and uniform distribution of grains are achieved with x=0.08.
• The two-phase coexistence and dense microstructure improve the electrical properties.
• Enhanced properties with d33=317 pC/N and kp=42.9% are obtained with x=0.08.

(1−x)(K0.445Na0.50Li0.055)NbO3–xBaZrO3 (KNNL–xBZ) lead-free piezoelectric ceramics were fabricated by the traditional sintering process. The effect of BaZrO3 on the phase structure, microstructure, and electrical properties were investigated. The XRD patterns confirm that BaZrO3 entirely diffused into (K0.445Na0.50Li0.055)NbO3 lattice to form new solid solutions, leading to a coexistence of rhombohedral and tetragonal phases with x=0.08. Enhanced electrical properties of d33=317 pC/N, kp=42.9%, εr=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.