Phase structure and electrical properties of (0.8−x) BaTiO3–0.2Bi0.5Na0.5TiO3–xBaZrO3 lead-free piezoceramics

► A morphotropic phase boundary (MPB) between tetragonal and pseudocubic phases of (0.8−x) BaTiO3–0.2Bi0.5Na0.5TiO3–xBaZrO3 ceramics exists at x=0.03–0.04. ► A relaxor behavior is induced after the addition of BaZrO3. ► The tetragonal–cubic phase transition shifts towards lower temperatures with increasing x. Lead-free piezoelectric ceramics (0.8−x)BaTiO3–0.2Bi0.5Na0.5TiO3–xBaZrO3 (BT–BNT–xBZ, 0≤x≤0.08) doped with 0.3wt% Li2CO3 were prepared by conventional solid-state reaction method. With the Li2CO3 doping, all the ceramics can be well sintered at 1170–1210°C. The phase structure, dielectric, ferroelectric and piezoelectric properties of the ceramics were investigated. Results show that a morphotropic phase boundary (MPB) between tetragonal and pseudocubic phases exists at x=0.03–0.04. The addition of Zr can improve the piezoelectric properties of BT–BNT ceramics. Furthermore, a relaxor behavior is induced and the tetragonal–cubic phase transition shifts towards lower temperatures after the addition of Zr. The ceramics with x=0.03 possess the optimum electrical properties: d33=72 pC/N, kp=15.4%, ɛr=661, Pr=18.5μC/cm2, Ec=34.1kV/cm, Tc=150°C.