Sr(Zn 1/3 Nb 2/3 )O 3 -induced R 3 c to P 4 bm transition and large field-induced strain in 0.80(Bi 0.5 Na 0.5 )TiO 3 –0

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Sr(Zn1/3Nb2/3)O3-induced R3c to P4bm transition and large field-induced strain in 0.80(Bi0.5Na0.5)TiO3–0.20SrTiO3 ceramics Qiumei Wei1, Mankang Zhu1,a), Mupeng Zheng1, Yudong Hou1,b) 1

Key Laboratory of Advanced Functional Materials, Ministry of Education, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China a) Address all correspondence to these authors. e-mail: [email protected] b) e-mail: [email protected] Received: 19 October 2018; accepted: 20 February 2019

Bi0.5Na0.5TiO3 (BNT)-based lead-free materials are important for piezoelectric actuator, and several researchers have studied the effect of B-site complex ion doping on strain in (Bi0.5Na0.5)TiO3–SrTiO3. In this work, a paraelectric perovskite Sr(Zn1/3Nb2/3)O3 (SZN) with B-site complex structure was introduced into 0.80 (Bi0.5Na0.5)TiO3–0.20SrTiO3 (BNTST) to investigate the phase structure and electrical properties as well as the field-induced strain behavior. The results showed that SZN substitution decreases the rhombohedrality 90-c and induces the transition from dominant ferroelectric to nonergodic relaxor by shifting its TF-R to lower temperatures. Moreover, the field-induced ferroelectric domains cannot remain stable at room temperature when SZN substitution is large than 1.0 mol%. These behaviors induced the transition between nonergodic relaxor and ergodic relaxor, which contributed to its large strain and related properties. In this work, this material gave the largest bipolar strain of 0.43% and large normalized unipolar strain of 505 pm/V at the SZN content of 2 mol% under 8 kV/mm, and showed good temperature stability up to 100 °C. The above encouraging results may be helpful for further investigation of BNTST-based ternary systems in search of a potential Pb-free piezoelectric material.

Introduction Piezoelectric actuator is an important device that can output precisely controlled displacement during the application of electric field and is widely used to drive motors in lots of advanced engineering systems. Up to now, the commercially available materials used for piezoelectric actuator are dominated by lead-based ceramics due to their excellent piezoelectric properties, such as perovskite lead zirconate titanate Pb (ZrxTi1x)O3 [1, 2]. However, due to the negative environmental impact of lead-containing substances, developing environmentally friendly lead-free piezoelectric materials is of great importance and with urgency [3, 4]. Among the developed lead-free materials, BNT-based lead-free piezoceramics are considered as one of the most promising candidates due to their high field-induced strain level [5, 6]. Especially in the latest decade, MPB solid solutions based on BNT were designed

ª Materials Research Society 2019

and investigated extensively due to their enhanced strain properties, such as (Bi1/2Na1/2)TiO3–BaTiO3 [7], BNT– Bi0.5K0.5TiO3 [8, 9], and BNT–SrTiO3 (BNTST) [1]. Moreover, the current understanding suggests that the choice of a system undergoing a similar field-induced phase tra