Strain Properties Of BNT-based Lead-free Textured Piezoelectrics By Template Grain Growth Method

The piezoelectric material is one of the modern high-tech material, widely used in transducers, actuators, sensors etc. Traditional high-performance piezoelectric ceramic lead zirconate titanate(Pb Zrx Ti1-x O3, PZT) is prohibited by international law, since it releases more and more lead into the environment. There had been many attempts by researchers in the past to develop alternative lead-free materials but the piezoelectric properties of lead-free piezoelectric ceramics are nowhere near to the PZT system. In addition to using the traditional method of doping or to create a new system to improve its performance, textured method can be used to improve its piezoelectric properties. In this work, the piezoelectric properties of Sodium bismuth titanate(Bi0.5Na0.5Ti O3, BNT)based lead-free piezoelectrics are improved by using texturing methods. The <001>oriented BNT based piezoelectric ceramic were prepared by template grain growth(TGG)method.In order to obtain high grain matching template. At first, Bi4Ti3O12(BIT) single crystal platelets were synthesized using a molten salt synthesis method. In the second step,BIT particles were used as precursors to synthesize NBT platelets by a topochemical reaction. We analyzed the phase structure and microstructure of Bi T and BNT template under different heat treatment conditions. The BNT particle can be fabricated by using the plate-like particle which is parallel to(001) plane with a width of 4-16 ?m and a thickness of about 0.5 ?m.The BNT system lead-free piezoelectric ceramics 0.852BNT-0.12BKT-0.028 BT and 0.91BNT-0.06BT-0.03 KNN were selected as the research objects,to improve theirstrain performance by the TGG method. The results show that the grain orientation of the ceramic is related to the sintering temperature and the content of the template. The orientation degree(Lotgering factor) of 0.852BNT-0.12BKT-0.028 BT ceramics was 63%when the content of the template was 5wt.% and the sintering temperature was 1160?.But its strain performance has not been improved, which may be due to the low degree of sample orientation and composition deviated from the MPB by BNT template doping.It was demonstrated that textured 0.91BNT– 0.06BT–0.03 KNN samples had a high bipolar strain of 0.226 %, which are 48.7 % higher than the randomly oriented samples.For fabricating 0.91BNT-0.06BT-0.03 KNN textured ceramics, TGG method with BNT template is more suitable. This work shows that under the right preparation, preferred orientation of grains is helpful to improve the strain properties of BNT-based ceramics.