Enhanced piezoelectric coefficient of HfO2-modified (K0.44Na0.56)0.94Li0.06(Nb0.94Sb0.06)O3 lead-free ceramics

(K0.44Na0.56)0.94Li0.06(Nb0.94Sb0.06)O3–xHfO2 (KNLNS–xHfO2) lead-free piezoceramics were prepared using the conventional solid-state method, and effects of HfO2 content on their microstructure and electrical properties were investigated. Their phase structure is independent of the HfO2 content (x=0–0.008). As the HfO2 content increases, the grain size, the Curie temperature, and the dielectric constant decrease. The ceramic with x=0.004 has enhanced electrical properties, i.e., d33~266 pC/N, kp~42.1%, εr~950, tanδ~0.027, and TC~343 °C, showing that adding HfO2 enhances the piezoelectric properties of KNLNS ceramics.