“…Moreover, high piezoelectric coefficient (d 33 ) and electromechanical coupling factor (k p ) are also required for high torque output and efficiency. For piezoelectric properties enhancement, Pb(Zr,Ti)O 3 (PZT) based ternary or quaternary systems, such as PZN-PZT [5], PMN-PZT [6], PMN-PZN-PZT [7], PMN-PFW-PZT [8], have been intensively investigated. It is reported that in these systems, ceramics with compositions near the morphotropic phase boundary (MPB) always possess optimum properties.…”