Large piezoelectricity in Pb-free 0.96(K_0.5Na_0.5)_0.95Li_0.05Nb_0.93Sb_0.07O₃-0.04BaZrO₃ ceramic: A perspective from microstructure

We employ transmission electron microscopy to explore the reason for large piezoelectricity (d₃₃≈400pC/N) in a Pb-free 0.96(K_0.5Na_0.5)_0.95Li_0.05Nb_0.93Sb_0.07O₃ -0.04BaZrO₃ ceramic from microstructure. The result shows that the high piezoelectricity corresponds to a miniaturized nanodomain configuration in a domain hierarchy. The nanodomains disappear on heating accompanied by a reduction in d₃₃ value. Further convergent beam electron diffraction study reveals a coexistence of tetragonal and orthorhombic phase, which indicates that large piezoelectricity of KNLNS_0.07-BZ may stem from easy polarization rotation due to low polarization anisotropy on the tetragonal-orthorhombic phase boundary.