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

Lead-free 0.985[(0.94− x)Bi_0.5Na_0.5TiO₃-0.06BaTiO₃- xSrTiO₃]-0.015LiNbO₃ [( 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 ( d₃₃). 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-0.03 ST)- LN exhibited a maximum unipolar strain of ~0.44% and corresponding normalized strain, S_max/ E_max of ~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-field-induced 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 ~490 pm/V even at 120°C. These findings indicated that the ( BNT- BT- xST)- LN system would be a suitable environmental-friendly candidate for actuator applications. [ABSTRACT FROM AUTHOR]