Large electromechanical strain and electrostrictive effect in (1-x) (Bi_(0.5)Na_(0.5)TiO_3-SrTiO_3)-xLiNbO_3 ternary lead-free piezoelectric ceramics

摘要

Lead-free (1-x)(0.8Bi(0.5)Na(0.5)TiO(3)-0.2SrTiO(3))-xLiNbO(3) (BNST-xLN, x=0-0.08) piezoelectric ceramics were fabricated by a solid-state sintered technology. The effects of LN-doping on the structural and electrical properties of the BNST-xLN system were systematically investigated. The results of Raman spectroscopy revealed that the substitution of LN softens the phonon vibrations in the BNST-xLN system, in accordance with the remarkable reduction in the phase transition temperature (TF-R), remnant polarization (P-r), negative strain (S-neg) and piezoelectric coefficient (d(33)). However, the degradation of the long-range ferroelectric orders was accompanied by a significant increase in the electric field-induced strain response. At x=0.04, a maximum unipolar strain of 0.36% with a corresponding normalized strain (S-max/E-max) of 600pm/V was obtained at room temperature, which should be mainly ascribed to the reversibly electric field-induced phase transition between the ergodic relaxor and ferroelectric phases due to their comparable free energies in the two-phase coexistence region. Moreover, it was also found that the BNST-xLN system processes predominant electrostrictive behaviors with relatively high electrostrictive coefficient (Q(33)) and excellent temperature stability when the field-induced phase transition cannot be trigged by the applied electric field, as evidenced by a fact that the Q(33) value of BNST-0.08LN ceramic keeps almost constant as high as 0.028m(4)/C-2 in the temperature range from room temperature to 120 degrees C.