Zn-Bi共掺杂Ba_(0.2)Sr_(0.8)TiO_3陶瓷结构及介电性能的研究

Study on the Structure and Dielectric Properties of Zn-Bi Co-doped Ba_(0.2)Sr_(0.8)TiO_3 Ceramics

采用传统固相反应法制备了ZnO的摩尔数为O．04，系列Zn-Bi共掺杂Ba0.2Sr0.8TiO3（BST）的陶瓷材料，包括BST＋0．04ZnO＋xBizO，（X=0．02，0．025，0．03）．用X射线衍射、扫描电子显微镜和变温介电谱方法，对它们的晶格结构、微观形貌和复介电常数进行了测量和分析．结果表明：（1）Zn2＋和Bi3＋进入到BST晶格中并与之形成ABO3钙钛矿型固溶体；（2）随Bi2O3的掺入，陶瓷的室温晶系结构由立方相转变为四方相，同时出现在--120K的弥散相变转化为弛豫相变；（3）Bi2O3掺杂对晶粒生长有明显的抑制作用，但晶粒之间的连接性增强，陶瓷的致密度增加；（4）当T=300K，f=1Hz，Bi2O3掺杂量为0．025mol时，陶瓷试样介电常数最大（857），介电损耗最小（8X10。）．上述结果对该类陶瓷掺杂改性研究以及弛豫相变机制探索无疑有一定的参考价值．

A series of Zn-Bi co-doped Bao.2Sr0.sTiO3 （BST） ceramics with ZnO molar content being 0.04 were prepared by conventional solid state reaction method, including BST＋0.04ZnO＋xBi203 （x=0.02, 0.025, 0.03）. The crystal structure, surface morphology and complex dielectric constant of the ceramics were measured and analyzed by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and dielectric spectroscopy methods. The results show that： （1） Zn2＋ and Bi3＋ were co-doped into the BST crystal lattice, and they form solid solution of ABO3 perovskite; （2） with Bi203 doping, the crystal structures of the ceramic samples change from the cubic （BST＋0.04ZnO） to tetragonal （BST＋0.04ZnO＋xBi203）, and the diffuse phase transition near M20K changes to the relaxation phase transition; （3） Bi203 doping significantly inhibits the growth of grains, but enhances the connection between the grains and consequently leads to the increase of the ceramic density; （4） When T=300K, f=l Hz, and the doping amount of Bi203 is 0.025mol, the dielectric constant of the ceramic sample has a maximum value （857）, and the dielectric loss is smallest （8×10-3）. The above results undoubtedly have a certain reference value to the doping modifications of this ceramic class, as well as to the studies of the relaxation phase transition mechanism.