A位元素非化学计量Bi_(0.5)(Na,K)_(0.5)TiO_3-BiFeO_3压电陶瓷

A-SITE NONSTOICHIOMETRIC Bi_(0.5)(Na,K)_(0.5)TiO_3-BiFeO_3 PIEZOELECTRIC CERAMICS

采用传统陶瓷制备方法,制备了A位元素非化学计量无铅压电陶瓷0.79(Bi0.5Na0.5)tTiO3–0.18(Bi0.5K0.5)tTiO3–0.03BitFeO3(t=0.95～1.05)。研究了A位元素非化学计量对该体系陶瓷微观结构、压电性能的影响,同时通过测量不同外加应力下压电应变常数(d33),研究了影响d33和径向机电耦合系数(kp)的不同机理。结果表明:A位元素缺乏较多时,析出第二相。kp随A位元素过量与不足的增加而减少,d33随A位元素过量的增加基本不变,随A位元素不足的增加而减少。采用极化相位角(θmax)衡量陶瓷极化程度,发现kp随θmax增加而增加,d33随θmax增加变化不明显。d33在低于临界应力时基本不变,当应力高于临界应力后,随应力增加而下降。压电陶瓷中的应力场对畴壁运动与弹性偶极子的作用是影响d33的作用机理之一。

An A-site nonstoichiometric lead-free piezoelectric ceramic 0.79（Bi0.5Na0.5） tTiO3–0.18（Bi0.5K0.5） tTiO3–0.03BitFeO3（t = 0.95–1.05） was prepared by a conventional ceramic sintering technique. The effect of A-site nonstoichiometry on the microstructure and piezoelectric properties was investigated. The different mechanisms between piezoelectric constant（d33） and radial electrome-chanical coupling factor（kp） were also investigated by measuring d33 under different stresses. An obvious second phase was observed for the sample with high A-site deficiency, kp decreases with the increase or decrease of A-site deficiency or excess A-site deficiency, d33 decreases with increasing A-site deficiency, and varies insignificantly with increasing A-site excess. The poling state was judged by the θmax of impedance in the inductance region between the resonance and anti-resonance frequency. It is found that kp increases and d33 shifts insignificantly with increasing θmax. d33 changes insignificantly when the stress is lower than a critical stress, and decreases with further increasing stress. The effect of internal stress on the elastic dipole and domain wall is one of the mechanisms of d33 variation.