Composition-driven phase evolution and piezoelectric properties of (1-x)(K0.48Na0.52)(0.96)Li0.04Nb0.95Sb0.05O3-xBi(0.5) (Na0.84K0.16)(0.48)Ba0.02ZrO3 lead-free ceramics

In this study, we investigated the correlation between the phase structure, electrical properties and composition of lead-free (1-x)(K0.48Na0.52)(0.96)Li0.04Nb0.95Sb0.05O3-xBi(0.5)(Na0.84K0.16)(0.48)Ba0.02ZrO3 ceramics, which were prepared by a normal oxide sintering method. X-ray diffraction analysis revealed that all the studied compositions had a pure perovskite structure. Meanwhile, the structural evolution with composition was researched by combining the x-ray diffraction results with the temperature-dependent dielectric data, and a rhombohedral-tetragonal phase boundary was identified to exist in x = 0.01 to 0.05. Additionally, the grain size of the ceramics was found to gradually decrease with the increase of x, due to the inhibition effect of added Bi3+, Ba2+ and Zr4+ ions on the growing of the grains during sintering process. The ceramics exhibited the optimal piezoelectric properties at compositions near the phase boundary, with the highest piezoelectric constant d(33) and the largest planar electromechanical coupling coefficient k(p) of 262 pC/N and 0.42, respectively.