【作者】 陈尚坤；

【导师】 杨辉；

【作者基本信息】 浙江大学 ， 材料学， 2004， 硕士

【摘要】 低温烧结微波介质陶瓷材料研究近年受移动通信事业的推动，发展非常迅速，为了满足微波器件小型化的需要，迫切需要开发高介电常数的低温烧结微波介质材料。Ba_6-3xLn_8+2xTi₁₈O₅₄（Ln为Sm、Nd、La等稀土元素）固溶体是典型的高介电常数微波介质陶瓷（ε＞80），在微波通讯技术中有着重要的应用。 根据陶瓷-银电极共烧要求，本文选用Bi₂O₃、BaCuO₂-CuO（简称BCC）、ZnO-B₂O₃-SiO₂（ZBS）、BaO-B2O₃-SiO₂（简称BBS），系统研究了烧结条件及成分变化对Ba_6-3xYd_8+2xTi₁₈O₅₄高介电常数微波介质陶瓷的烧结性能、相组成、显微结构和微波介电性能之间的关系。在此基础上，先利用Bi部分置换Nd，再掺加BCC／ZBS、BCC／BBS助剂，协同降低Ba_6-3xNd_8+2xTi₁₈O₅₄陶瓷的烧结温度并协调微波介电性能。 （一）基础配方的选择及改性优化 Ba_6-3xNd_8+2xTi₁₈O₅₄陶瓷在0.5≤x≤0.8范围内，随着x的增加，介电常数呈下降趋势，在x=2／3时出现异常增大现象；Q·f值则先增后减。x=2／3，陶瓷为纯净的单相固溶体，Q·f达到最大值，x＞2／3，有第二相Nd₂Ti₂O₇出现，导致Q·f下降。在用Bi对Nd置换的陶瓷中，随着Bi置换量的增加，致密化烧结温度降低，介电常数增加，而Q·f保持在较高的数值。 （二） 单一助剂BCC降低烧结温度 Ba_6-3xNd_8+2xTi₁₈O₅₄陶瓷致密化温度先随BCC量的增加而下降，随之基本保持变化。掺加量2.5～15wt％时，烧结温度均在1150℃，这与BCC的低共熔点温度较高密切相关，单一掺加BCC助剂降低烧结温度效果有限。BCC相作为第2相分布在晶界或晶粒处，Ba_6-3xNd_8+2xTi₁₈O₅₄陶瓷介电常数和Q·f值随BCC添加量增加而下降。 （三）复合助剂低温烧结研究 采用ZBS／BCC、BBS／BCC复合助剂，促使Ba_6-3xNd_8+2xTi₁₈O₅₄陶瓷在较低温度下结晶充分，可以与Cu、Ag电极共烧。固定BCC添加量，随着ZBS、BBS添加量增加，介电常数先降低后上升，并保持良好的Q·f值。Ba₄(Nd_0.85Bi_0.15)_28／3Ti₁₈O₅₄陶瓷在复合添加2.5wt％BaCuO₂-CuO和5wt％BaO-B₂O₃-SiO₂后可以在950℃烧结成致密瓷，在5.6GHz，介电常数ε为60.25，Q·f值为2577GHz，频率温度系数τ_f为+25.1ppm／℃。 本研究通过对Ba_6-3xNd_8+2xTi₁₈O₅₄陶瓷体系的配方改性和复合添加烧结助剂，得到了一种性能优良、可用于多层片式微波频率器件的低温烧结微波介质陶瓷。更多还原

【Abstract】 With the quick increasment of mobile telecommunication industry, low temperature cofirable ceramics are developed very quickly. In order to fulfil the need of LTCC design, not only the low- ε materials but also high- ε materials should be developed. Ba6-3xLn8+2xTi18O54 solution is the most important high- ε material and can be used as key materials in duplexer.In this thesis, effects of composition and sintering temperature upon the sintering characteristics, phase composition, microstructures and microwave dielectric characteristics of Ba6-3xNd8+2xTi18O54 high-ε microwave dielectric ceramics were investigated. Modification of microstructure and microwave dielectric properties were conducted by Bi substitution for Nd, add BCC, ZBS, BBS in the Ba6-3xNd8+2xTi18O54 ceramics.With increasing x of Ba6-3XNdg+2XTi18O54 ceramics(0.5 ≤ x≤ 0.8), dielectric constant decreased as a whole but at x=2/3 there was a break and got the maximum, while Q f factor increased first then decreased and at got the maximum at x=2/3.Effects of composition and sintering temperature upon the microwave dielectric characteristics of Ba6-3X(Nd1-y,Biy)8+2XTi18054(x=2/3) ceramics were investigated. With the increasing Bi content in the ceramics, sintering temperature decreased, dielectric constant increased and the Q f factor kept at a high level.Adding BCC as a sintering aid, with the increasing amount of BCC in Ba6-3XNd8+2XTi18O54, dielectric constant and Q f factor decreased, while sintering temperature decreased first then kept steady, this was close related to the high melting point.With the multiplex aids of ZBS/BCC BBS/BCC, Ba6-3xNd8+2xTi18O54 ceramics could be sintered at a low temperature, and could be cofired with Cu or Ag electrode. With invariable amount of BCC, with increasing amount of ZBS or BBS in Ba6-3xNd8+2xTi18O54, dielectric constant decreased first and then increased while the Q f factor kept a good value. When 2.5wt%BCC and 5wt%BBS were added,Ba4(Nd0.85Bi0.15)28/3Ti18O54 ceramics could be sintered at 950℃, and at 5.6GHz, ε = 60.25, Q f=2577GHz, τ f=+25.1ppm/℃Though modification of Ba6-3xNd8+2xTi18O54 and addition of multiplex sintering aids, a series of low-firing high- ε microwave dielectric ceramics used as multi-layer components can be achieved.更多还原