Large strain response in (Bi0.5Na0.5)TiO3-6BaTiO3-based lead-free ceramics at high temperature

Lead-free ceramics have attracted considerable research attention owing to their environmentally friendly properties as well as their relatively good piezoelectric properties. Herein, we doped BiCoO3 (BCO) onto (Bi0.5Na0.5)TiO3-6BaTiO(3) (BNT-6BT) solid solution at various concentrations and investigated their dielectric and piezoelectric properties. After comparing the Rietveld refinement data with X-ray diffraction (XRD) results, it was found that all the BNT-6BT-xBCO ceramics (x = 0, 0.5%, 1%, and 1.5%) showed the morphotropic phase boundary conformation with coexisting tetragonal (P4bm) and cubic (Pm 3(_) m) phases. XRD refinement data also demonstrated that with increasing BCO concentration to 1.5%, the mole ratio between the tetragonal and cubic phases was close to 1:1, which enhanced the piezoelectric performance of the ceramic composites. At a BCO concentration of 1.5%, the strain and piezoelectric coefficient (d(33)) of the sample reached 0.31% and 196 pC/N, respectively. The highest effective d(33)* of 489 pm/V was obtained at 110 C with BNT-6BT-1.5BCO ceramics. The BNT-6BT-xBCO ceramics show great promise for use in high-temperature actuator applications.