(Ba, Ca)(Ti, Zr)O 3 -BiFeO 3 lead-free piezoelectric ceramics Jiagang Wu a, * , Wenjuan Wu a , Dingquan Xiao a , John Wang b , Zhenchun Yang b , Zhihang Peng a , Qiang Chen a , Jianguo Zhu a a Department of Materials Science, Sichuan University, Chengdu, China b Department of Materials Science and Engineering, National University of Singapore, Singapore 117574, Singapore article info Article history: Received 23 June 2011 Received in revised form 11 August 2011 Accepted 26 August 2011 Available online 13 September 2011 Keywords: Lead-free piezoelectric ceramic BiFeO 3 Microstructure Electrical properties abstract Effects of BiFeO 3 (BFO) content on the microstructure and electrical properties of Ba 0.85 Ca 0.15 Ti 0.90 Zr 0.10 O 3 (BCTZ) ceramics prepared by normal sintering in air were investigated. A stable solid solution is formed between BCTZ and BFO. The grain size gradually becomes smaller, and the ceramics become denser with increasing the BFO content. The Curie temperature, dielectric constant, and dielectric loss of BCTZ ceramics decrease simultaneously with the introduction of BFO. Moreover, the remanent polarization reaches a maximum at x ¼ 0.2 mol%, and the coercive field continuously increases with increasing the BFO content due to the introduction of BFO with a higher coercive field. Improved piezoelectric prop- erties (d 33 w 405 pC/N and k p w 0.44) are demonstrated for the BCTZ ceramic with x ¼ 0.2 mol%. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Lead-based piezoceramics play a leading role in the field of piezoelectric materials because their piezoelectric properties are superior to those of lead-free materials [1e3]. However, consider- able attention has been recently given to the development of lead- free piezoceramics due to their environmental issues [4e7]. For a long period of time, two materials are as the leading candidates, K 1-x Na x NbO 3 (KNN) [4e7] and Bi 0.5 Na 0.5 TiO 3 [8,9]. Although considerable efforts have been conducted to improve their piezo- electric properties, their piezoelectric constant is still poorer than that of lead-based materials [1,4e10]. Moreover, a low density is also a serious drawback for the KNN -based ceramics in the prac- tical application [1,4,11]. Therefore, it is necessary to find a new lead-free material system to exceed or compare the piezoelectric properties of lead-based materials. BaTiO 3 (BTO) is a traditional material in the field of piezoceramics [12], while poor piezoelectric properties are often observed for the BTO ceramics [13]. The d 33 value of BTO ceramics has been improved greatly by different sintering techniques, such as microwave sin- tering, ordinary sintering, and two-step sintering, the high d 33 values of 350e460 pC/N have been demonstrated [14e17]. Recently, a surprisingly high d 33 value of w620 pC/N has been reported for the BTO-based ceramics prepared by inducing a tricritical triple point [18], indicating that it is feasible for the BTO-based ceramics to replace the lead-based piezoelectric materials. Some researchers also find that it is very difficult to get the Ca and Zr -modified BTO ceramics with a high density when sintered in air, where these ceramics are sintered in an oxygen atmosphere [19]. BiFeO 3 (BFO) as a rare single phase material is extensively investigated because of the coexistence of both polar and magnetic orders at room temperature, a high Curie temperature (T c w 1100 K), the G-type antiferromagnetic spin ordering, and a cycloid-type spatial spin modulation occurs below the Ne’el temperature (T N w 640 K) [20,21]. It has been reported that an enhancement in piezoelectric properties has been observed by forming the solid solution of BFO and lead-free materials, such as Na 0.5 K 0.5 NbO 3 eLiSbO 3 eBiFeO 3 [22], (1-x)Na 1/2 Bi 1/2 TiO 3 -xBiFeO 3 [23], and Na 0.5 K 0.5 NbO 3 eBiFeO 3 [24]. In the present work, (1-x)(Ba 0.85 Ca 0.15 )(Ti0 .90 Zr 0.10 )O 3 exBiFeO 3 [(1-x)BCTZ-xBFO] ceramics were prepared by normal sintering in air. Effects of BFO content on the microstructure and electrical properties of (1-x)BCTZ-xBFO ceramics were investigated. These results show that the (1-x)BCTZ-xBFO ceramics with a high density and good electrical properties are induced by doping an optimum BFO content. 2. Experimental procedure BaCO 3 (99%), CaCO 3 (99.9%), TiO 2 (99%), ZrO 2 (99%), Bi 2 O 3 (99.9%), and Fe 2 O 3 (99%) powders were used as raw materials. * Corresponding author. E-mail address: wujiagang0208@163.com (J. Wu). Contents lists available at SciVerse ScienceDirect Current Applied Physics journal homepage: www.elsevier.com/locate/cap 1567-1739/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2011.08.016 Current Applied Physics 12 (2012) 534e538