Compositional inhomogeneity and segregation in (K_0.5Na_0.5)NbO₃ ceramics

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• 作者：Kepi Chen^a ; ^{ckp@ncepu.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Jing Tang^a ; Yan Chen^b
• 关键词：Lead-free piezoelectric ; Compositional inhomogeneity ; Compositional segregation ; Liquid phase sintering ; Potassium&ndash ; sodium niobate ; Calcination temperature
• 刊名：Ceramics International
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：42
• 期：8
• 页码：9949-9954
• 全文大小：2904 K

文摘

In this report, the effects of the calcination temperature of (K_0.5Na_0.5)NbO₃ (KNN) powder on the sintering and piezoelectric properties of KNN ceramics have been investigated. KNN powders are synthesized via the solid-state approach. Scanning electron microscopy and X-ray diffraction characterizations indicate that the incomplete reaction at 700 °C and 750 °C calcination results in the compositional inhomogeneity of the K-rich and Na-rich phases while the orthorhombic single phase is obtained after calcination at 900 °C. During the sintering, the presence of the liquid K-rich phase due to the lower melting point has a significant impact on the densification, the abnormal grain growth and the deteriorated piezoelectric properties. From the standpoint of piezoelectric properties, the optimal calcination temperature obtained for KNN ceramics calcined at this temperature is determined to be 800 °C, with piezoelectric constant d₃₃=128.3 pC/N, planar electromechanical coupling coefficient k_p=32.2%, mechanical quality factor Q_m=88, and dielectric loss tan δ=2.1%.