High strain in lead-free Nb-doped Bi_1/2(Na_0.84K_0.16)_1/2TiO₃–SrTiO₃incipient piezoelectric ceramics

Abstract

Lead-free 0.96[Bi1/2(Na0.84K0.16)1/2(Ti(1−x)Nbx)O3]–0.04SrTiO3 (BNKTN–ST, with x = 0–0.030) ceramics were synthesized by a conventional solid-state reaction technique. Polarization and strain hysteresis loops indicated a significant disruption of ferroelectric order accompanied by an enhanced field-induced strain (S = 0.438%) with a high normalized strain Smax/Emax of 876 pm/V at 5 kV/mm. Their reproducibility was confirmed by the fabrication of a 10-layered stack-type multilayer actuator, which demonstrated a normalized strain Smax/Emax of 720 pm/V.

Giant strain with low cycling degradation in Ta-doped [Bi1/2(Na0.8K0.2)1/2]TiO3 lead-free ceramics

“…10,12,15 The corresponding d 33 * is 1240 pm/V, a 42% enhancement over the best value reported in literature for (Bi 1/2 Na 1/2 )TiO 3 -based compositions. 22 Such a giant electrostrain and ultrahigh d 33 * are even comparable with some (Bi 1/2 Na 1/2 )TiO 3 -based single crystals. 26,27 The strain in the BNT-1.5Ta ceramic was also measured under unipolar electric fields and a slightly smaller d 33 * value of 1120 pm/V was observed at 50 kV/cm.…”

“…Very recently, a high electrostrain of 0.438% was observed at a moderate electric field of 50 kV/cm, corresponding to a high d 33 * value of 876 pm/V, in a Sr and Nb co-doped [Bi 1/2 (Na 0.84 K 0.16 ) 1/2 ]TiO 3 ceramic. 22 It appears that Sr enhances d 33 * by shifting the depolarization temperature T d toward room temperature. 23 The contribution of Nb to the high electrostrain lies in its donor dopant nature, suppressing oxygen vacancy formation and transforming the mixed rhombohedral and tetragonal phases into a pseudocubic relaxor phase.…”

Evolution of phase structure and giant strain at low driving fields in Bi-based lead-free incipient piezoelectrics

“…Doping of impurities, either on the A-or Bsites of the ABO 3 perovskite structure, has been found as an effective method to enhance EFIS [19,[25][26][27][28]. Previously SZmodified BNBT ceramics demonstrated an improvement in dielectric and piezoelectric performance with a piezoelectric constant (d 33 ) of 197 pC/N [29].…”

“…Several researchers have attempted to lower this E th and improve the electric field-induced strain (EFIS) response [17][18][19][20][21][22][28][29][30][31][32][33][34][35][36]. Doping of impurities, either on the A-or Bsites of the ABO 3 perovskite structure, has been found as an effective method to enhance EFIS [19,[25][26][27][28].…”

Effect of Nb Doping on the Dielectric and Strain Properties of Lead–free 0.94(Bi1/2Na1/2)TiO3–0.06BaTiO3 Ceramics

“…3) In BNTbased or BNKT-based lead-free relaxor ceramics, the usual strain level reaches ~ 0.4 % with a small amount of chemical modifications, [7][8][9][10][11][12] which is almost twice the usual strain of PZT ceramics. This large electromechanical strain is known to result from a reduction in the remanent strain, S rem , 13) due to the presence of a nonpolar phase (more precisely an ergodic relaxor, ER) [14][15][16] at 'zero' electric field.…”