Dielectric Properties Of Barium Zirconate Titanate Ceramics

Barium titanate ceramics, which have been developed over the last decades, are a kind of new functional ceramics. Today, they have been one of the most important functional ceramics used as the basic raw materials in the composition of ceramic capacitors. As a high performance ferroelectric materials, barium titanate has been developed into a new kind of functional ceramic since Wainer and Selomon found its good dielectric properties in 1942. But the T_c of Barium titanate is about 120℃which restricts its application in room temperature. Doped barium titanate is the preferred research direction to improve the dielectric properties of barium titanate. In recent years, the research of Ba(Zr_xTi_1-x)O₃ is popular because that the Zr⁴⁺ is much more stable than Ti⁴⁺ and the Tc of Ba(Zr_xTi_1-x)O₃ can be shifted into room temperature.Many methods were used to Prepare barium titanate ceramics, solid-phase reaction of their simple process, high yield and low cost in the industry has been extensively applied. In this paper, barium zirconate titanate ceramics were prepared by solid-phase method and the sol-gel, and their morphology and structure and electrical properties were studied.Barium zirconate titanate Ba(Zr_0.2Ti_0.8)O₃ (BZT20) ceramics have been prepared by a sol-gel process. The phase structure and micrograph of the ceramics was determined by an x-ray diffraction and a scan electron microscope, respectively. The temperature dependence of dielectric permittivity of the ceramics has been investigated. The results show that the grain size of the BZT20 ceramics was about 60 urn, and the XRD patterns indicated a polycrystalline perovskite nature of a tetragonal phase at room temperature. Diffusion constant of BZT20 was about 1.64, which indicates that dispersion ferroelectric-paraelectric phase transition happened.Barium zirconate titanate Ba(Zr_xTi_1-x)O₃,(x=0.02,0.04,0.06,0.08,0.10, 0.12) lead-free ceramics were prepared by a solid-phase reaction. The influence of milling time, sintering temperature, molding pressure on property of BZT ceramics was considered. Test results showed that: with the increase of doped zirconium, XRD peaks shifted to the lower angle slightly, and (200/002) peaks merged slowly. That suggested zirconium doped adding barium zirconate titanate ceramics' lattice parameters. The Curie temperature of BZT ceramic lowered by zirconium doped. Electrical measurements show that area covered by electrical hysteresis loop gradually decreased with the increase of zirconium doped, which implied the polarization loss decreased accordingly.