Na_2O含量对BaO-SrO-Nb_2O_5-B_2O_3-SiO_2系玻璃陶瓷微结构和性能的影响

Effects of Na_2O content on microstructure and properties of NaO-BaO-SrO-Nb_2O_5-B_2O_3-SiO_2 system glass-ceramics

采用熔融法制备NaO-BaO-SrO-Nb2O5-B2O3-SiO2玻璃陶瓷。借助DSC、XRD、SEM和电学性能测试研究不同含量的Na2O对其相组成、显微结构、介电性能、体积电阻率及击穿强度的影响。结果表明:随着Na2O含量(摩尔分数)的增加,玻璃转变温度(Tg)和第一析晶放热峰(Tp1)温度逐渐降低,而第二析晶放热峰温度(Tp2)呈先降低后升高再降低的变化。经(800℃,3 h)+(900℃,3 h)热处理后,未添加Na2O的样品析出单相四方钨青铜结构的Ba0.5Sr0.5Nb2O6,而添加5%Na2O(摩尔分数)的样品变为单相Ba0.25Sr0.75Nb2O6。当Na2O为10%时,样品的主晶相仍为Ba0.25Sr0.75Nb2O6,但析出NaSr1.2Ba0.8Nb5O15和Na2Ba2Si2O7相;继续增加Na2O量到15%时,样品的晶相种类不变而衍射峰强度有所增强。样品的介电常数随Na2O含量的增加呈"N"字形变化,样品的体积电阻率和击穿强度随Na2O含量的增加而降低,未添加Na2O试样的击穿强度最大为1 500 kV/cm,其储能密度达3 J/cm3。

NaO-BaO-SrO-Nb2O5-B2O3-SiO2 glass-ceramics were prepared using melting method.The effects of different Na2O contents on the phase compositions,microstructure,dielectric properties,volume resistivity and breakdown strength were investigated by differential scanning calorimetry（DSC）,X-ray diffractometry（XRD）,scanning electric microscopy（SEM） and electrical property measurements.The results show that with increasing Na2O content,the glass transition temperature（Tg） and the first crystallization peak temperature（Tp1） gradually decrease,but the second crystallization peak temperature（Tp2） firstly decreases and then increases and finally decreases.Under the same heat treatment condition（（800 ℃,3 h）＋（900 ℃,3 h））,the single phase tetragonal tungsten bronze Ba0.5Sr0.5Nb2O6 occurs in the sample without Na2O.The pure phase,Ba0.25Sr0.75Nb2O6,is obtained when Na2O content（mole fraction） is 5%.As Na2O content（mole fraction） is 10%,the main crystalline phase is still Ba0.25Sr0.75Nb2O6,however,the phases of NaSr1.2Ba0.8Nb5O15 and Na2Ba2SiO6 appear.For the sample with 15%Na2O,the types of the crystalline phases are unchanged,but the intensity of the diffraction peak slightly increases.With increasing Na2O content,the dielectric constant of glass-ceramics changes like a ＂N＂ letter,while the breakdown strength and volume resistivity decrease.The sample without Na2O has the highest breakdown strength（1 500 kV/cm）,and its energy storage density is 3 J/cm3.