| The research and application of Barium Titanate (BaTiO3) based piezoelectric ceramic material has been very mature at present, and the related materials are widely used in the fields of light, sound, electronics and so on. In recent decades, these materials have attracted considerable attention as a kind of excellent ferroelectric materials. However, the low Curie temperature (Tc=120℃) and poor stability of temperature limit their application at room temperature.The Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3(abbreviated as BCZT) ceramic, as a new kind of binary-system ceramic materials, showed very high piezoelectric properties around morphotropic phase boundary (MPB), the value of d33can reach to600pC/N, which can be comparable with piezoelectric properties of lead-based ceramics materials. However, a series of disappointing shortcomings still exist in the material and limit its broader application. BCZT lead-free piezoelectric ceramics with high electric properties were successfully prepared by traditional solid phase reaction in this paper. The differences of TiO2powders and the effect of these TiO2powders on microstructures and electric properties of BCZT piezoelectric ceramics were investigated at first and then in view of the shortcomings of low Curie temperature and high sintering temperature, new ceramic systems were designed by doping and modification to improve Curie temperature and reduce the sintering temperature of the BCZT ceramics, aiming to providing a candidate of lead-free piezoelectric ceramics with excellent piezoelectric properties. The main results are as follows:1. The effect of TiO2on the phase structure, microstructure, dielectric, piezoelectric and ferroelectric properties of the BCZT ceramics was studied, respectively. The results were shown as that:there was an obvious difference in the phase structure between the two kinds of TiO2power, one was the pure rutile phase and another was a pure anatase phase. The best electric properties of the two series of ceramic samples were achieved after calcining at1200℃for4h and sintering at1440℃for6h. Using TiO2with a rutile phase as raw materials, BCZT ceramics exhibit electric properties as follows:d33=590pC/N, kp=0.46, Pr=11.18μC/cm2,Ec=2.38kV·cm-1,εr=2900, εm=14500, tanδ=0.014, Tc=91℃. BCZT ceramics using TiO2with an anatase phase as raw materials show electric properties as follows:d3=392pC/N,kp=0.41, Pr=8.89 μC/cm2,Ec=2.46kV·cm-1,εr,=2810, εm=11920, tanδ=0.016, Tc=91℃. In general, the BCZT piezoelectric ceramics prepared by the TiO2with a pure rutile phase possessed relatively higher comprehensive performance.2. BCZT ceramics with different contents of Ca0.28Ba0.72Nb2O6(abbreviated as CBN) additive were prepared, and the influences of the sintering temperature and CBN additive on the phase structure, microstructure, and electric properties of the BCZT ceramic were investigated, in detail. It was found that the Curie temperature was improved from91℃to98℃and the samples showed better electric properties when the content of CBN was0.2wt.%. Meanwhile all the samples exhibited pure perovskite phase. The properties were as follows:d33=560pC/N, tanδ=0.019, εr,=3724, Tc=98℃, εm=21215, Pr=10.12μC/cm2,Ec=1.62kV·cm-1.3. BCZT-xwt.%ZnO lead-free piezoelectric ceramics were successfully obtained at1350℃by conventional solid method, and the influences of the sintering temperature and ZnO additive on the phase structure, microstructure, and electric properties of the BCZT ceramics were investigated. It was found that the sintering temperature was reduced from1440℃to1350℃and showed better properties, when the content of ZnO was0.1wt.%. All the samples exhibited pure perovskite phase. The best properties were as follows:d33=649pC/N,kp=0.56, tanδ=0.019,εr,=3498,εm=17727, Tc=96℃, Pr=8.43p.C/cm2,Ec=2.37kV·cm-1, providing a promising candidate with good performance for practical applications.
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