【作者】 郭秀盈；

【导师】 张之圣； 吴霞宛； 肖谧；

【作者基本信息】 天津大学 ， 微电子与固体电子， 2006， 博士

【摘要】 Ag（Nb,Ta）O₃是一类高频高介的陶瓷材料,但是该材料在铌含量较高时,温度系数和损耗较大;而钽含量较高时,难以烧结成瓷。本论文通过优化合成工艺路线得到了性能优良的Ag（Nb,Ta）O₃固溶体,然后通过B位Nb/Ta比及非化学计量比、相似离子对A位Ag⁺离子或B位Nb⁵⁺/Ta⁵⁺离子取代以及添加助剂对其结构、微观形貌及介电性能的影响,揭示了一些ANT改性的基本规律,得到了可低温度烧结、介电性能优异的Ag（Nb,Ta）O₃基陶瓷材料。最后,进行了非常规合成法,如半化学法、晶种法等,制备Ag（Nb,Ta）O₃的尝试。结果表明,将Nb2O5、Ta2O5经高温（1200℃）煅烧,然后加入相应量的Ag₂O,再经950℃预烧的工艺为制备Ag（Nb,Ta）O₃陶瓷的最佳工艺。随Ta含量（x）的增加,Ag（Nb1-xTax）O₃的烧结温度越来越高;介电常数（ε）先增大后减小（x=0.4时,有εmax=516.8）,介电损耗（tanδ）单调减小,温度系数（αε）向负的方向移动。B位（Nb,Ta）少量缺位可以促进ANT烧结;而（Nb,Ta）过量会导致ANT样品半导化。与Ag+半径相近、价态相同的Na+离子的A位取代对Ag(Nb_0.8Ta_0.2)O₃介电性能的改善效果最佳,当Na+离子取代量x=0.1时,Ag1-xNax(Nb_0.8Ta_0.2)O₃有εmax值558.5,tanδmin值0.0017。与Nb⁵⁺/Ta⁵⁺离子半径相近、价态相同的适量Sb（x≤0.08）和Mn4+、W6+复合（x≤0.16）取代B位Nb⁵⁺/Ta⁵⁺离子,可以有效降低Ag(Nb_0.8Ta_0.2)O₃烧结温度,增大介电常数ε,减小介电损耗tanδ,Sb取代还可以明显减小温度系数;于1040℃烧结的Ag（Nb,Ta）1-xSbxO₃（x=0.08）样品有最佳介电性能:ε=982.4,tanδ≈0.0031,αε=163.1ppm/℃;Ag(Nb_0.8Ta_0.2)1-x（Mn,W）xO₃ （x=0.04, 0.08, 0.12, 0.16）样品的介电损耗值十分相近,在0.00156⁰.00179范围内,说明少量（Mn,W）复合取代就可以减小Ag(Nb_0.8Ta_0.2)O₃的损耗值。低熔点助剂的添加均可以通过液相烧结作用促进ANT烧结,Sb2O5和Bi2O₃的作用最明显,使ANT的损耗明显减小,介电常数增大,温度系数近于零;由于稀土元素（Y、Ce、Dy和Gd）的4f电子受到5s²5p⁶壳层的屏蔽,稀土元素掺杂对ANT介电性能无明显影响。由于Ag⁺离子强的还原性,水热法和熔盐法难以制备出符合化学计量比的ANT,而半化学法、晶种法可以改善ANT的烧结和介电性能。更多还原

【Abstract】 Ag（Nb,Ta）O₃ is a kind of high frequency ceramics with high permittivity. However, its temperature coefficient of permittivity and dielectric loss are large when Nb content is high, and it is difficult to be sintered when Ta content is high. In this study, Ag（Nb,Ta）O₃ ceramics was synthesized through the optimized processing route, and the effects of the Nb/Ta ratio at B-site and non stoichiometry, effects of oxide additives and the substitution of similar cations for Ag⁺ at A-site or Nb⁵⁺\Ta⁵⁺ at B-site on its crystal structure, microstructure and dielectric properties were also investigated. Some principles used for the modification of Ag（Nb,Ta）O₃ ceramics were suggested. Ag（Nb,Ta）O₃-based ceramics with good dielectric properties sintered at lower temperature were obtained. Finally, some untraditional synthesizing methods, such as semichemical or seeding method were attempted to prepare Ag（Nb,Ta）O₃.The results show that, the route that Nb2O5 and Ta2O5 firstly reacted at 1200℃, then mixed with Ag₂O and fired at 950℃, was the optimal processing route to prepare Ag（Nb,Ta）O₃ powders. With the Ta content increasing, the sintering temperature of Ag（Nb1-xTax）O₃ increased, permittivityεfirst increased and then decreased（x=0.4,εmax=516.8）, dielectric loss tanδmonotonically decreased and temperature coefficient of permittivityαεshift for the negative values. The studies of non stoichiometry at B-site showed that the deficiency of （Nb,Ta） could promote Ag（Nb,Ta）O₃ sintering, but excessive （Nb,Ta） would lead to the semiconducting. Dielectric properties of Ag(Nb_0.8Ta_0.2)O₃ ceramics were greatly improved by the substitution of Na+ for Ag+ ions at A-site, which has the same valence and similar radius. When Na+ content （x） is 0.1, Ag1-xNax(Nb_0.8Ta_0.2)O₃ ceramics has the maximum permittivityεmax of 558.5 and minimum loss tanδmin of 0.0017. Similarly, proper amount of Sb（x≤0.08） substitution or Mn4+ and W6+ （x≤0.16） co-substitution for B-site Nb⁵⁺/Ta⁵⁺ ions can decrease the sintering temperature of Ag(Nb_0.8Ta_0.2)O₃, increase its permittivityε, and decrease its dielectric loss tgδ. And Sb substitution can suppress the temperature coefficient of permittivity effectively. Ag（Nb,Ta）1-xSbxO（3x=0.08）ceramics sintered at 1040℃presented optimal dielectric properties:ε=982.4 , tanδ≈0.0031 andαε=163.1ppm/℃. The dielectric loss values of Ag(Nb_0.8Ta_0.2)x（Mn,W）1-xO₃ （x=0.04, 0.08, 0.12, 0.16） ceramics, 0.00156⁰.00179, are very low and close, which indicated that a little Mn4+ and W6+ co-substitution could decrease the dielectric loss of更多还原