钙钛矿/钨青铜两相复合BSTN陶瓷的形成与性能研究

Formation and Properties of the BSTN Composite Ceramics with Perovskite and Tungsten Bronze Phases

设计了特殊配方0.7BaO.0.3SrO·(1-y)TiO2·yNb2O5,通过过量组成控制,制备了钙钛矿相和钨青铜相共存的复相陶瓷.用XRD和阻抗仪测试了相结构及介电常数.结果表明,在形成以钙钛矿为主相的体系中,Nb2O5过量6mol％以上时开始形成钨青铜相;在形成以钨青铜为主相的体系中,BaO和SrO过量11mol％以上时开始形成钙钛矿相.两相含量相当的体系中,钙钛矿相几乎不固溶Nb2O5,而钨青铜相固溶一定量TiO2.复相陶瓷的介电性能具有BST和SBN两相的特点.BSTN复相体系中钨青铜相的铁电/顺电转变温度随固溶TiO2量增加而降低,随钙钛矿相增加而升高,其最低转变温度约在200℃,比纯SBN相下降90℃.

Special compositions of Ba0.7Sr0.3.(1 - y)TiO3.yNb(2)O(5) were designed for preparing the BSTN system by the traditional ceramic method. The composite ceramics in which the two phases of the perovskite (BST) and the tungsten bronze (SBN) coexist were successfully prepared by this composition controlled in the excessiveness of some components. XRD and LCR were used to measure the structure and dielectric constants of the composite ceramics. It is found that, in the perovskite (BST) structured system of BSTN ceramics, the second phase SBN starts to appear when the excessive content of Nb2O5 is up to about 6mol%. Similarly, in the tungsten bronze (SBN) structured system, the second phase of BST can also begin to form while the excessive content of (BaO+SrO) is up to about 11mol%. However, both the perovskite and the tungsten bronze phases formed in a system exhibit the different minorities of Nb2O5 and TiO2 solved respectively with changing the excessiveness. Especially in the case of the two phases being equivalent to each other in BSTN composite ceramics, Nb2O5 is hardly to be solved into the perovskite phase due to shortage of Nb2O5 and excessiveness of TiO2 in composition. However, a few of TiO2 is easily to be solved in the tungsten bronze phase due to excessiveness of TiO2.There is a dual characteristic shown by the perovskite phase and the tungsten bronze phase in temperature dependence curve of dielectric constant in the BSTN. The Curie temperature of the tungsten bronze phase decreases with the increase in solubility of TiO2 in the phase structure. Conversely, the Curie temperature increases with increasing perovskite phase due to the primary effect of the tungsten bronze phase being restricted by a lot of perovskite. The lowest transition temperature between ferroelectric and paraelectric phases in the BSTN is at about 200 degreesC and it is 90 degreesC lower than that of the SBN without TiO2 solved in the present work.