Giant electromechanical strain response in lead-free SrTiO3-doped (Bi0.5Na0.5TiO3-BaTiO3)-LiNbO3 piezoelectric ceramics

Lead-free 0.985[(0.94-x) Bi0.5Na0.5TiO3-0.06BaTiO(3)-xSrTiO(3)]-0.015LiNbO(3) [(BNT-BT-xST)-LN, x=0-0.05] piezoelectric ceramics were prepared using a conventional solid-state reaction method. It was found that the long-range ferroelectric order in the unmodified (BNT-BT)-LN ceramic was disrupted and transformed into the ergodic relaxor phase with the ST substitution, which was well demonstrated by the dramatic decrease in remnant polarization (P-r), coercive field (E-c), negative strain (S-neg) and piezoelectric coefficient (d(33)). However, the degradation of the ferroelectric and piezoelectric properties was accompanied by a significant increase in the usable strain response. The critical composition (BNT-BT-0.03ST)-LN exhibited a maximum unipolar strain of similar to 0.44% and corresponding normalized strain, S-max/E-max of similar to 880 pm/V under a moderate field of 50 kV/cm at room temperature. This giant strain was associated with the coexistence of the ferroelectric and ergodic relaxor phases, which should be mainly attributed to the reversible electric-fieldinduced transition between the ergodic relaxor and ferroelectric phases. Furthermore, the large field-induced strain showed relatively good temperature stability; the S-max/E-max was as high as similar to 490 pm/V even at 120 degrees C. These findings indicated that the (BNT-BT-xST)-LN system would be a suitable environmental-friendly candidate for actuator applications.