Preparation And Study Of High-Dielectric Constant And Low Dielectric Loss Glass-Ceramics

BaO-SrO-PbO-TiO2-SiO2-Nb2O5 nanocomposite dielectrics containing both niobate and titanate ceramic phases were successfully prepared via melt-quenching followed by controlled crystallization.On the basis of this system,by adjusting the content of SiO2,TiO2 to optimize the types and proportions of precipitated ceramic phases,and adding Al2O3 and rare earth oxides to further improve the properties of the precipitated ceramic phase,it is expected to obtain a high dielectric constant,low dielectric loss glass ceramic system.High dielectric constant niobate and titanate ceramic phases were simultaneously precipitated in the BaO-SrO-PbO-TiO2-SiO2-Nb2O5 glass-ceramic system through composition and process optimization.After crystallization at 800 0C,Pb2Nb2O7,(Ba,Sr,Pb)Nb2O6 and(Sr,Pb)TiO3 phases precipitate in the glass matrix.With the crystallization temperature increases,the Pb2Nb2O7 phase with pyrochlore structure disappears.After crystallized at 900 ℃ and 1000 ℃,there exist only(Ba,Sr,Pb)Nb2O6 and(Sr,Pb)TiO3 crystal phases.The size of the crystalline grains increases significantly after the crystallization at 1000 ℃ and the maximum grain size reaches about 500 nm.Two kinds of glass ceramic samples with excellent dielectric properties were obtained by adjusting the SiO2 content and crystallization temperatures.In the aspect of high dielectric constant,the glass-ceramic samples with a SiO2 molar ratio of 16 obtains a high dielectric constant of 1070 and the dielectric loss of 0.0045 after crystallized at 1000 ℃.In the aspect of low dielectric loss,the glass-ceramic samples with a SiO2 molar ratio of 20 achieves a very low dielectric loss of 0.0008 and a moderate dielectric constant of 430 at the crystallization temperature of 800 ℃.In addition,in the study of TiO2 content in the system,the peak dielectric constant of the glass-ceramic samples with a TiO2 molar ratio of 10 was obtained.The addition of Al2O3 enhances the dielectric properties of the BaO-SrO-PbO-TiO2-SiO2-Nb2O5 glass-ceramic system at a low temperature of 800 ℃ after crystallization.However,after the crystallization treatment at 900 ℃ and 1000 ℃,the low-dielectric-constant silicate phase precipitated,resulting in a sharp drop in the dielectric constant and deterioration of the dielectric properties.The addition of trace rare earth oxides has a significant effect on the dielectric properties of the BaO-SrO-PbO-TiO2-SiO2-Nb2O5 glass-ceramic system.The dielectric constant of the samples after the addition of two rare earth oxides is significantly increased.After the crystallization at 1000℃,the dielectric constant of the sample added La2O3 increased by 10.2%,and the dielectric constant of the sample added Gd2O3 increased by 14.5%.The addition of two rare earth oxides has a significant effect on the leakage current density.After two rare earth oxides are added,the leakage current density is greatly reduced and the insulation performance is improved.The leakage current density in the glass-ceramic samples with a La2O3 molar ratio of 0.25 is reduced by an order of magnitude compared to the unaddition of the sample.