【作者】 彭娟；

【导师】 张显友；

【作者基本信息】 哈尔滨理工大学 ， 材料学， 2008， 硕士

【摘要】 四方钨青铜结构的铌酸锶钡(Sr_xBa_1-xNb₂O₆,0.25≤x≤0.75,简写为SBN)和钙钛矿结构的钛酸锶钡(Sr_xBa_1-xTiO₃,简写为BST)具有优良的电学性能,是实验研究和应用开发的热点。为了发掘两类材料更优异的性能进而探索其实际应用的可能性,人们开始研究SBN和SBT复合陶瓷的制备和介电性能。本文采用改进的溶胶凝胶法制备SBN和BST两相共存的复相陶瓷,简称BSTN,系统研究了其制备方法和及制备过程中各影响因素。同时分析了复相陶瓷体系中不同Sr/Ba比和Nb/Ti比对体系结构及介电性能的影响。采用X射线衍射仪（XRD）、扫描电子显微镜（SEM）等方法系统研究了BSTN的结构,并结合TG-DTA等分析手段对烧结制度进行了分析。通过阻抗测试仪及LCR数字电桥分析了BSTN复相陶瓷的介频特性及介温特性。本论文的研究表明:（1）与传统复相陶瓷的制备方法固相法相比,改进的溶胶凝胶法有利于两相的良好固溶,同时降低烧结温度并抑制晶粒的异常生长;（2）通过对前聚体干凝胶的热分析得到其最佳的预烧温度为800℃,并结合现有烧结炉制定出烧结过程中的升温曲线;（3）分析了烧结温度和烧结时间对复相陶制备的影响,得到:钙钛矿相BST的形成温度低于钨青铜相SBN,确定实验采用烧结温度1250℃烧结3h;（4）在x范围为0.25⁰.75之间钙钛矿相和钨青铜相可以良好的固溶在复相体系中。随着x值的增加复相陶瓷室温下的介电常数逐渐减小,而介电损耗逐渐增加。所以当体系Sr/Ba比为3/7时,介电常数较大的同时介电损耗较小,且居里温度在室温范围,对提高介电器件的性能有着重要的意义;（5）固定Sr/Ba比为3/7,系统研究了复相陶瓷0.7BaO·0.3SrO·（1-y）TiO2·yNb2O5的相组成和微观结构与Nb/Ti比的关系。随着体系中Nb5+含量的增加,其居里温度不断升高,介电常数和介电损耗都减小,当y=0.7时表现出良好的介频特性和温频特性,可以认为复相陶瓷的介电性能得到了很好的改善。更多还原

【Abstract】 Strontium barium niobate with tetragonal tungsten bronze structure and barium strontium titanate with perovskite structure have attracted lots of attention due to their outstanding dielectrical properties and potential applications. However SBN with defect that was difficult sintered to a high density and can abnormal grain grow. So the composite material with good dielectric properties, mechanical properties may be obtained by a composite of BST and SBN. In this paper (1-x)BaO·xSrO·(1-y)TiO2·yNb2O5(BSTN in short) with coexistence of the perovskite and tungsten bronze phases were successfully prepared by a modified sol-gel method, and the formation mechanism of the composite ceramics was investigated in details. The effect of different Sr/Ba ratio and Ni/Ti ratio to the structure and properties of the materials were also studied. Some instruments were chose included X-ray diffraction (XRD), scanning electron microscope (SEM), impedance instrument and also LCR digital bridge.Following results can be obtained from the paper: (1) Compare to the traditional solid method, this modified sol-gel can shorten the sintering time and lower the crystallizing temperature while with a good combination of the two phase without any abnormal grain growth; (2) The presintering temperature was chosen at 800℃through thermal analysis and a heating cure was made; (3) By analysis the sintering mechanism can got that the formation temperature of SBN is higher than that of BST, and the composite ceramics sintering temperature was determined at 1250℃for 3h; (4) BST and SBN can be coexisted in the system well with the x value in range of 0.25~0.75. With the increasing of x value, dielectric constant became lower while the dielectric loss increase. So, the composite ceramic with x=0.3 possess higher dielectric constant and lower dielectric loss means more to improve the dielectrical device; (5) In 0.7BaO·0.3SrO·(1-y)TiO2·yNb2O5 system, with the increasing of y value the material perform a better dielectric property, especially when y=0.7. So, the dielectric properties of composite ceramic were improved largely.更多还原