Studies On The Preparation And Properties Of (Bi_1/2Na_1/2)TiO₃-Bi（B’B"）O₃lead-Free Piezoelectric Ceramics

Piezoelectric ceramics is an important functional material based on its mutualtransfer between mechanical energy and electric energy. While the widely used lead-based piezoelctric ceramics has brought about serious lead pollution due to their hightoxicity. Environmental issues call for the use of non-hazardous materials in devicefabrication. Therefore, considerable effort has been devoted to develop the lead-freepiezoceramics with properties comparable to PZT. Among them,(Bi0.5Na0.5)TiO3-based piezoceramics have drawn lots of attentions as one category of candidates toreplace Pb-based materials.In this paper,(1-x)(Bi1/2Na1/2)0.96Ba0.04TiO3-xBi(Zn1/2Ti1/2)O3(BNBTZ100x)and (1-x)(Bi1/2Na1/2)0.875Ba0.125TiO3-xBi(Mg1/2Ti1/2)O3（BNBTM100x） lead-freepiezoelectric ceramics modified were prepared by the conventional mixed oxidemethod. Microstructures were studied according x-ray diffraction, scanning electronmicroscope and transmission electron microscope etc. Dielectric, piezoelectric,ferroelectric and field induced strain properties were measured by multi-frequencyinductance capacitance resistance (LCR) analyzer, d33meter, ferroelectric tester etc.According, composition and temperature depedence evolution of these propertieswould be discussed.Results of BNBTZx implied that: with BZT addition, the phase structure ischanging to pseudocubic from rhombohedral, means the structure symmetry isimproving with the increasing content of BZT, which have strong relationship withthe shrong relaxor characteristics. Beside this analyzing the P(E) and thermaldepolarization data show a enhanced relaxor behavior with the BZT addition. Afterthat, further investing of dielectric date through Modified-Curie law show aobviously enhance of the diffuse phase transition and frequency dispersion witchconfirm the conclusions of the P(E) date. The reason of it maybe the Mixed occupiedof B-site ions and the different structure of the the substrate material and BZT.Results of BNBTZx implied that: BMT induces the crystal structuretransformation from long range tetragonal phase to dispersed pseudocubic phase(PNRs), trace amount of PNRs (BMT≤2mol.%) soften the long range ferroelectricdomains leading to the improvement of the piezoelectric properties. As a BNT-basedpiezoceramics, excellent piezoelectric properties (165pC/N) was achieved (2mol.%BMT). The amount of PNRs increase with the BMT contents, when ceramics expressthe dispersion characteristics at room temperature, the field induced transformationfrom dispersed phase to ferroelectric phase improves the field induced strain propertyand achieved the best performance at BNBTM4. Accroding to the reports and our experiments, Bi-based perovskite Bi(B′B″)O3enharce the dispersion characteristics of BNT-based cramics because of its’ mixedoccupied of B-site ions. As a reasult, Bi(B B)O3could improve the field induced strainproperties rather than modified the depolarization hehavior of BNT-base carmics.