Diffusion phase transition and impedance spectroscopy of Bi2O3/CuO co-doped BCZT lead-free ceramics
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Perovskite type (Ba0.85Ca0.15−2x Bi2x )(Zr0.1Ti0.9−x Cu x )O3 lead-free ceramics were prepared via a conventional solid-state reaction method. The phase structure, dielectric, ferroelectric properties and complex impedance were investigated in detail. XRD and dielectric measurements determined that single orthorhombic phase displayed in (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 at room temperature. With the introduction of Bi2O3/CuO, the phase structure exhibited the mixture of orthorhombic and tetragonal phases, and then turned to single tetragonal phase. In contrast to the sharp dielectric transition of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramics, a broad dielectric peak coupled with a slight decrease in Curie temperature was observed in (Ba0.85Ca0.15−2x Bi2x )(Zr0.1Ti0.9−x Cu x )O3 ceramics with increasing x. The observed diffuse phase transition behavior was further confirmed by a couple of measurements with polarization loops and polarization current density curves. The structural and the composition fluctuations induced by ions doping should be responsible for the diffuse phase transition behavior. Furthermore, physical mechanisms of the conduction and relaxation processes were revealed by using impedance spectroscopy analyses. It was concluded that the conduction and relaxation processes were thermally activated, which was closely linked with the singly and doubly ionized oxygen vacancies.
KeywordsBaTiO3 Bi2O3 Ferroelectric Property Morphotropic Phase Boundary Diffuse Phase Transition
This work was supported by National Science Foundation of China (NSFC) (Grant Nos. 51172136, 21401123 and 51107077), the Fundamental Research Funds for the Central Universities (Program Nos. GK201403006, GK201402061, GK201301002, GK201101003 and GK201101004), the Science and Technology Program of Shaanxi Province (Grant Nos. 2013K09-26 and 2013JM2013), education department of Shaanxi Provincial Government (Grant No. 12JK0631), Scientific and Technology Research Project in Xi’an [Program No. CXY1342(4)].