不同TiO_(2)和Nb_(2)O_(5)含量对BaO-SrO-PbO-TiO_(2)-Nb_(2)O_(5)-SiO_(2)玻璃陶瓷介电性能的影响

TiO_(2)and Nb_(2)O_(5)Content on Dielectric Properties of BaO-SrO-PbOTiO_(2)-Nb_(2)O_(5)-SiO_(2)Glass-Ceramics

使用熔融-快冷-可控结晶技术,制备出了不同TiO_(2)和Nb_(2)O_(5)含量的Ba O-Sr O-Pb O-TiO_(2)-SiO_(2)-Nb_(2)O_(5)纳米复合介电材料,并对其介电性能进行了研究。结果表明:800℃结晶处理后的样品析出了烧绿石结构Pb_(2)Nb_(2)O_(7)相、钨青铜结构(Ba,Sr,Pb)Nb_(2)O_(6)相和钙钛矿结构(Sr,Pb)TiO_(3)相,其中Pb_(2)Nb_(2)O_(7)相衍射峰强度随TiO_(2)/Nb_(2)O_(5)比例的上升而增强;900和1000℃结晶处理后,TiO_(2)含量较多的样品中依然存在Pb_(2)Nb_(2)O_(7)相,且衍射峰强度随结晶处理温度的上升而下降。微观结构分析结果显示在1000℃结晶处理后,所有样品的晶体颗粒近似球形。通过对Ba O-Sr O-Pb O-TiO_(2)-SiO_(2)-Nb_(2)O_(5)体系中TiO_(2)与Nb_(2)O_(5)含量的调整,获得了介电性能突出的玻璃陶瓷样品,TiO_(2)含量为12%,Nb_(2)O_(5)含量为24%的玻璃陶瓷样品获得了最大介电常数(~1310),同时介电损耗维持在0.0093的较低水平,作为高压陶瓷电容器介质展现出了良好的应用前景。

The glass-ceramic dielectric material is a composite material of glass and ceramic phase coexist.The glass-ceramic can achieve complete densification and possess high breakdown field strength.It can precipitate high dielectric constant ceramic phase through controlled crystallization process,so that the glass-ceramic has moderate dielectric constant.Therefore,as a new type of dielectric energy storage material,dielectric glass-ceramic has a good prospect in the application field of high-voltage capacitors.However,the low dielectric constant and high dielectric loss of glass-ceramic hinder the further development of this material.In this paper,titanate ceramic phase was introduced into niobate glass-ceramic system to increase the dielectric constant and alkali metal ions with small radius were removed to reduce the dielectric loss.Ba O-Sr O-Pb O-TiO_(2)-SiO_(2)-Nb_(2)O_(5)nanocomposite dielectric materials with different TiO_(2)and Nb_(2)O_(5)contents were prepared via melting-quenching-controlled crystallization technology.And the effect of TiO_(2)and Nb_(2)O_(5)contents on properties of Ba O-Sr O-Pb O-TiO_(2)-SiO_(2)-Nb_(2)O_(5)glass-ceramic system were characterized by X-ray diffraction(XRD),differential thermal analysis(DTA),scanning electron microscopy(SEM)and dielectric properties test.The results showed that the crystallization activation energy decreased gradually with the value of TiO_(2)/Nb_(2)O_(5)increased,which meant that the increased of TiO_(2)/Nb_(2)O_(5)ratio in Ba O-Sr O-Pb O-TiO_(2)-SiO_(2)-Nb_(2)O_(5)glass-ceramic system was conducive to crystallize.XRD results showed the glass samples all had obvious amorphous characteristics,indicating there was no crystal phase precipitation in the glass matrix.The samples after crystallization treatment at800℃precipitated pyrochlore structure Pb_(2)Nb_(2)O_(7)phase,tungsten bronze structure(Ba,Sr,Pb)Nb2O6 phase and perovskite structure(Sr,Pb)TiO_(3)phase,and the intensity of the diffraction peak of Pb_(2)Nb_(2)O_(7)phase increased as the value of TiO_(2)/Nb_(2)O_(5)increased.It meant that the increased of TiO_(2)/Nb_(2)O_(5)ratio promoted the precipitation of Pb_(2)Nb_(2)O_(7)phase.With the increased of crystallization temperature,the diffraction peak intensity of Pb_(2)Nb_(2)O_(7)phase gradually decreased,but the diffraction peak intensity of(Sr,Pb)TiO_(3)and(Ba,Sr,Pb)Nb2O6 phase gradually increased.The results indicated that the increase of crystallization temperature inhibited the formation of Pb_(2)Nb_(2)O_(7)phase but promoted the growth of(Sr,Pb)TiO_(3)and(Ba,Sr,Pb)Nb2O6 phase.After the crystallization treatment at 900℃and 1000℃,Pb_(2)Nb_(2)O_(7)phase still existed in the samples with more TiO_(2)content,but the diffraction peak intensity decreased with the increase of the crystallization treatment temperature.The microstructure analysis results showed that after crystallization treatment at 1000℃,the crystal particles of all samples were approximately spherical.The dielectric properties test showed that the dielectric constant and dielectric loss of the glass-ceramic sample increased with the increase of the crystallization temperature.This was attributed to the growth of ceramic phase with the increased of crystallization temperature.After crystallization at 800℃and 900℃,the dielectric constant gradually decreased with the increase of the TiO_(2)/Nb_(2)O_(5)ratio,which caused by the precipitation of the low dielectric constant pyrochlore structure Pb_(2)Nb_(2)O_(7)phase.After crystallization at 1000℃,it was found that the dielectric constant increased firstly and then decreased with the increase of the ratio of TiO_(2)/Nb_(2)O_(5).The increase in dielectric constant was due to the change in the composition that promoted the precipitation of the perovskite structure titanate ceramic phase.The decrease in dielectric constant related to the precipitation of low dielectric constant phases.The glass-ceramic samples with excellent dielectric properties were obtained by adjusting TiO_(2)and Nb_(2)O_(5)contents.The maximum dielectric constant(~1310)of the glass-ceramic with 12%TiO_(2)and 24%Nb_(2)O_(5)contents was obtained,and the dielectric loss kept at a low level of 0.0093.The dielectric constant of glass-ceramic with TiO_(2)content of 10%and Nb_(2)O_(5)content of 26%decreased slightly,but still higher than 1000,and dielectric loss decreased to 0.0079.Since no alkali mental ions with small radius were introduced into system,the dielectric loss kept below 0.01.At the same time,it had good temperature stability of dielectric constant,and the fluctuation range of dielectric constant was less than 10%at-40~80℃.It was also found that the polarization curves of glass-ceramic were slender,the residual polarization intensity was small,and the energy loss was small in the charging and discharging process,indicating that the material had high energy release efficiency.Therefore,Ba O-Sr O-Pb O-TiO_(2)-Nb_(2)O_(5)-SiO_(2)glass-ceramic as high voltage ceramic capacitor medium showed a good application prospect.