硅酸盐学报

通过溶胶凝胶法合成含Mn的复合氧化物Y3MgMnxSi O7.5+x(x=0.1,0.2,0.5,1.0)纳米掺杂剂,并采用纳米掺杂工艺制备BaTi O3基多层陶瓷电容器瓷料。采用热重差热分析、X射线衍射、透射电子显微镜对干凝胶及其焙烧粉体进行表征,并研究了纳米掺杂剂中Mn离子对陶瓷微观结构、介电性能以及抗还原性的影响。结果表明干凝胶经650,750,850,950℃焙烧后获得平均粒度分别为25.9,40.2,51.8,67.9nm的Y3MgMnxSi O7.5+x纳米粉,在850℃附近从无定形态向结晶态转变。Mn能够显著地抑制BaTi O3基陶瓷的晶粒生长并提高均匀性和致密性,平均晶粒尺寸约0.4μm。随着纳米掺杂剂中Mn含量的增加,陶瓷由四方晶型向赝立方晶型转变,并促使“壳芯”结构的形成,从而显著改善介电温度特性并提高室温介电常数(ε25℃≥2600)。纳米掺杂剂中多价态Mn离子作为受主能抑制自由电子浓度,增强瓷料的抗还原性,使瓷料的介质损耗减小(tanδ<1.0%),绝缘电阻率提高(ρ=1012Ω·cm),符合EI A X7R/X8R标准。

Nano-composite oxide dopant Y_3MgMn_xSiO_ 7.5+x (x=0.1,0.2,0.5,1.0) was synthesized by the solgel method and BaTiO₃-based ultrafine nonreducible dielectrics for multilayer ceramic capacitance were prepared by the nano-doping process. Xerogel and calcined nanopowder were characterized by thermogravimetricdifferential thermal analysis, X-ray diffraction and transmission electron microscopy. The effect of manganese ion in nano-dopant on the microstructure and dielectric properties as well as the non-reducibility of BaTiO₃-based ceramics were investigated. The results indicate that the average particle size of nanopowder Y_3MgMn_xSiO_ 7.5+x calcined at 650, 750, 850℃ and 950℃ is about 25.9, 40.2, 51.8nm and 67.9nm, respectively, and the BaTiO₃-based nanopowder begins to crystallize around 850℃. Mn can dramatically inhibit the grain growth of BaTiO₃ -based ceramics and promote the formation of fine grain structure (average grain size about 0.4μm). With the increase of Mn content in nano-dopant, the crystal structure of ceramics transform from tetragonal to pseudocubic and the coreshell structuses are perfectly formed. Accordingly, the dielectric temperature characteristics are improved and the permittivity at room temperature is more than 2600. Multivalent Mn ion in nano-dopant acting as an acceptor can effectively restrain the electronic concentration and reinforce the non-reducibility of the ceramics. Dielectric loss of the ceramic is lower than 1.0 % and insulation resistivity increases to 10 12 Ω·cm consequently. BaTiO₃-based dielectrics with high performances can be obtained to meet the requirements of EIA X7R/X8R standards.