Comparison of Ferroelectric and Strain Properties between BaTiO₃- and BaZrO₃-Modified Bi_1/2(Na_0.82K_0.18)_1/2TiO₃Ceramics

Abstract

Effects of BaTiO3 (BT) and BaZrO3 (BZ) modification on the crystal structure and electromechanical properties of lead-free Bi1/2(Na0.82K0.18)1/2TiO3 (BNKT) ceramics were compared within a doping range of 0–5 mol %. The differences between BT- and BZ-modification effects were clearly observed in polarization and electric field-induced strain hysteresis loops. BZ-modification induced a gradual transition from a ferroelectric to a nonpolar phase, resulting in an abnormal enhancement in the electric field-induced strain (EFIS) just after the transition. However, all BT-modified specimens showed strong ferroelectricity without abnormal enhancement in EFIS. The results suggest that Zr doping-induced B-site strains play a significant role in the ferroelectric-to-nonpolar phase transition in the Bi-perovskite.

Comparative Study of Conventional and Microwave Sintering of Large Strain Bi-Based Perovskite Ceramics

“…The small P r value of CFS-derived specimens is also in agreement with previously reported results on BZ-modified BNKT ceramics [32,33,35], indicating that the BZ-modification induced a phase transition in the BNKT from ferroelectric to relaxor. On the other hand, such a phase transition was not observed in the MWS-derived specimens, which exhibited values of P r from 20 to 54 μC/cm 2 , and of E c from 16 to 21 kV/cm, as shown in Fig.…”

“…In the case of CFS, both P r and E c initially increased with T s , and then decreased when T s reached 1100°C. All the CFS-derived specimens showed much smaller P r and E c values than those of BNKT, which have been reported as P r = 30 μC/cm 2 and E c = 35 kV/cm [32].…”

“…It was also reported that the increased sintering temperature in (Na 0.5 K 0.5 )NbO 3 -based materials can enhance ferroelectricity [39] or rhombohedral symmetry in MWS-derived specimens [16,[23][24][25][26][27][28][29][30][31]. Previous studies on the effect of BaZrO 3 (BZ)-modification on the crystal structure of BNKT ceramics [32] have found that the BZ modification induces a phase transition from rhombohedral to pseudocubic symmetry. However, the present results suggest that MWS inhibits the rhombohedral-to-pseudocubic transition.…”

“…The large strain observed at the normal and relaxor ferroelectric phase boundary was recently found to be closely related to the nanoscale composite of the normal and relaxor ferroelectric phases [30]. In particular, BaZrO 3 -modified Bi 1/2 (Na,K) 1/2 TiO 3 (BNKT) was found to exhibit not only relatively large strains (above 400 pm/V) but also small strain hysteresis, when compared with other bismuthsodium-titanate-based compounds [32][33][34][35]. These advantages make it a promising material for a wide range of precision mechatronic systems, such as fuel injectors for diesel and gasoline engines, position control systems for precision stages, and electronic motors, where low voltage driving is strongly required.…”

Current Development in Lead-FreeBi0.5(Na,K)0.5Quan1, Bac2, Thiet3 et al. 2014Advances in Materials Science and Engineering

“…In fact, the solid solution with small amount (∼several mole percents) of O 3 perovskite ceramics was two times higher than undoped case [97]. In addition, they pointed out that the modification EFIS of BaZrO 3 was better than that of BaTiO 3 [98]. The electric-field-induced strain was significantly enhanced by the CaZrO 3 -induced phase transition and reached the highest value of max / max of 617 pm/V when were also found to enhance the electromechanical properties when those were solute in Bi 0.5 (Na,K) 0.5 TiO 3 [103][104][105][106][107][108][109].…”