Dielectric properties of the fluorite-like Bi2O3-Nb2O5 solid solution and the tetragonal Bi3NbO7
Dielectric properties of the fluorite-like Bi2O3-Nb2O5 solid solution and the tetragonal Bi3NbO7
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DOI：
10.1111/j.1151-2916.2003.tb03401.x
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发表时间：
2003-06
影响因子：
3.9
通讯作者：
M. Valant;D. Suvorov
中科院分区：
文献类型：
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作者：
M. Valant;D. Suvorov
我们对δ-Bi2O3Nb2O5固溶体(δ-BNSS)的微波介电性能的分析表明，随着Nb2O5浓度的增加，介电常数和介电损耗不断增加。唯一不连续的是共振频率的温度系数，在整个均匀性范围内为负值，但在Nb2O5含量为20mol%时达到最小值。在相同成分下，δ-BNSS陶瓷的晶粒度不连续。对于Nb2O5含量为25mol%的样品，观察到了两种结构变化。单相四方相Bi3NbO7，在文献中称为III型相，在850°C到880°C的非常窄的温度范围内形成。低于或高于该温度范围进行的合成导致形成δ-BNSS均一范围的末端成员。与δ-BNss相比，Bi3NbO7陶瓷具有较低的微波介电损耗、较高的电导率和正的谐振频率温度系数。
Our analysis of the microwave dielectric properties of the δ-Bi2O3–Nb2O5 solid solution (δ-BNss) showed a continuous increase in permittivity and dielectric losses with an increasing concentration of Nb2O5. The only discontinuity was found for the temperature coefficient of resonant frequency, which is negative throughout the entire homogeneity range but reaches a minimum value for the sample with 20 mol% Nb2O5. At the same composition there is a discontinuity in the grain size of the δ-BNss ceramics. For the sample containing 25 mol% Nb2O5 two structural modifications were observed. A single-phase tetragonal Bi3NbO7, in the literature referred to as a Type-III phase, is formed in a very narrow temperature range from 850° to 880°C. A synthesis performed below or above this temperature range resulted in the formation of the end member of the δ-BNss homogeneity range. Compared with the δ-BNss the Bi3NbO7 ceramics exhibit lower microwave dielectric losses, an increased conductivity, and a positive temperature coefficient of resonant frequency.