Preparation And Dielectric Characterazation Of Strontium Barium Niobate Glass Ceramics With Tungsten Bronze Structure

In this paper, the SBN glass ceramics with tungsten bronze structurewere prepared by bulk crystallization method at950oC. Effects ofcrystallization time, addition of nucleating agents and their contents onthe crystallization mechanism, microstructure, crystal constitutes,dielectric and energy storage properties for the SBN glass ceramics weresystematically studied by DSC, SEM, OM, XRD, IS and P-E loopmeasurement. Crystallization mechanism, the microstructure-macrodielectric properties relations as well as the polarons types were furtherdiscussed based on from these results.1) Using the Kissinger equation, the value of Eacalculated fromDSC results is462kJ/mol, which is nearly equal to the dissociationenergy of Si-O bond. It indicates a Si-O breakage controlling process forthe SBN precipitation. OM results showed an obvious surfacecrystallization phenomenon for the SBN glass ceramics.2) Crystallization time （t） has a significant influence on themicrostructure and dielectric properties of the SBN glass ceramics. Thethickness of crystal layer exhibits a parabolic law with the variation of t.With the rise of t from0to8h, both the SBN crystal size and content first increased and then remained the same. Correspondingly, the value ofdielectric constant increased from10to460. Moreover, as the t increased,the Curie point shifted to high temperature before bulk crystallization.This phenomenon is attributed to the compositional fluctuation andclamping effect.3) The addition of TiO₂decreased the crystallization temperature forSBN glass system and promoted the crystal precipitation process. As thecontents of TiO₂increased from0to1mol%, the crystal size increasedfirst and then decreased while the same trend was observed for the changeof dielectric constant. The value of dielectric constant for the sample with0.1mol%TiO₂is510, which increased about160compared with theliterature. In addition, the maximum energy density was calculated to be0.13J/cm3.4) The addition of0.1mol%ZrO2decreased the crystallizationtemperature from1000oC to957oC. Compared to the samples withoutnucleating agents, both the SBN crystal size and its uniformity increased.Besides, the dielectric constant increased about50and the saturationpolarizationenhanced about1.5μC/cm2. The maximum energy densitywas calculated to be0.21J/cm3, which got about0.07J/cm3higher.5) The value of relaxation activation energy for SBN crystal phase isabout1.0eV while a little higher value was obtained for the glass phase.The results indicate an oxygen vacancy polarization process for SBNcrystal and a combination of oxygen vacancy and other ion polarizationmechanism for the glass phase.