Study On Preparation And Properties Of（1-x）BaTi_0.8Zr_0.2O_3-xBa_0.7Ca_0.3TiO₃Lead-free Piezoelectric Ceramics

In this paper, a series of (1-x)BaTi0.8Zr0.2O3-xBa0.7Ca0.3TiO3(BZT-BCT)(x=0.1-0.9) lead-free piezoelectric ceramics were prepared using sol-gel technique. The aim is to find out the most excellent composition of ferroelectric, dielectric and piezoelectric properties from different compositions of BZT-BCT ceramics through different analysis and comparison of the performance of BZT-BCT ceramics. Furthermore, in terms of the optimal composition ceramic, firstly, study is conducted on optimal composition ceramic microstructure, morphology and the relationship of the electrical properties and the sintering temperature at different sintering temperatures; secondly, in the preferred sintering temperature, influence to optimal composition ceramic electric hysteresis loops and polarization switching current caused by of the electric field, frequency and temperature is researched, analyzing ceramic polarization switching process of the optimal composition.XRD test results of BZT-BCT ceramics of different compositions show that all samples prepared at a sintering temperature of1330℃have typical perovskite structure, suggesting that Ca and Zr diffuse into the BaTiO3lattice to form a solid solution; at room temperature, BZT-BCT ceramics appeared the coexistence of the orthorhombic phase and the tetragonal phase between0.2and0.6. In addition, with the increase of x, Zr content is reduced, resulting in the interplanar crystal spacing decreases, so that the diffraction peak in the vicinity of45°to a trend of moving to a large angle.SEM results of test on different compositions BZT-BCT ceramics show that, the surface morphology of this composition ceramic is best when x=0.1with even grain size, a high degree of densification, and the smallest average grain size.Electric properties test on BZT-BCT ceramics of different compositions show that when x=0.1, the ferroelectric, dielectric and piezoelectric properties of the ceramic are at the best level, which is because morphortropic phase boundary is most easily approached, so come its most excellent electric properties, thus further verify the morphotropic phase boundary theory. When the frequency reaches0.001Hz, the maximum dielectric.constant is29,218; At room temperature, the remnant polarization and the coercive field are9.05μC/cm2and86.4V/mm, and the d33value of the maximum piezoelectric coefficient can reach to675pm/V.These studies have shown that when the sintering temperature is1330℃, ceramics of x=0.1composition (ie:(Ba0.97Ca0.03)(Ti0.82Zr0.18)O3, BCZT in short) possess excellent microstructure and electric properties.For optimal composition (Ba0.97Ca0.03)(Ti0.82Zr0.18)O3ceramics, sintered at different temperatures (1290-1330℃), all the BCZT ceramics have a typical perovskite structure, and at different sintering temperature coexistence state of rhombohedral and tetragonal phase exists in BCZT ceramics; when the sintering temperature is1330℃, BCZT ceramic gains even grain size, a high degree of densification, and the smallest average grain size, and BCZT ceramics exhibits anomaly in all of the properties such as the highest spontaneous polarization Pm, highest remnant polarization Pr, lowest coercive field Ec, and higher dielectric permittivity ε. Especially when the sintering temperature is1330℃maximum piezoelectric coefficient of BCZT ceramic is d33=675pm/V. On the other hand, the effect of electric field on hysteresis loops of BCZT ceramics are analyzed, and polarization switching process of the BCZT ceramics is explored.