Low-temperature sintering and enhanced dielectric properties of alkali niobate ceramics prepared from solvothermally synthesized nanopowders

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• 作者：Qilin Gu^a ; ^b ; Qiaomei Sun^a ; ^b ; Kongjun Zhu^a ; ^{kjzhu@nuaa.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Jinsong Liu^b ; Jinhao Qiu^a
• 关键词：Low-temperature sintering ; Sodium niobate ; Dielectric properties ; Solvothermal synthesis
• 刊名：Ceramics International
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：43
• 期：1
• 页码：1135-1144
• 全文大小：1761 K

文摘

Sodium niobate nanopowders (N-NaNbO₃) and submicron powders (M-NaNbO₃) were synthesized by the solvothermal and hydrothermal route, respectively. Subsequently, their sintering activities were comparably investigated through a modified solid-state sintering process. It's found that N-NaNbO₃ green bodies presented an apparent shrinkage after the calcination at 650 °C, and dense N-NaNbO₃ ceramics can be obtained at 950 °C. Besides, the optimized sintering temperature of N-NaNbO₃ ceramics was 100 °C lower, yet the shrinkage was four times larger when compared with M-NaNbO₃ samples. Importantly, N-NaNbO₃ samples showed improved dielectric properties in the whole frequency range, and the room temperature relative dielectric constant (ε_r) of N-NaNbO₃ samples sintered at 950 °C was as high as ~8000. The improved permittivity of N-NaNbO₃ samples was attributed to the compact microstructure, unique crystalline structure and less oxygen vacancies. At the same time, the effect of abnormal phase transition behavior originated from the metastable structure was considered to explain the enhanced room temperature permittivity. It's believed that the solvothermal route has great potentials in the synthesis of alkali niobate ceramics powders with high activity for low-temperature sintering.