Microwave dielectric properties of Na_0.5Sm_0.5TiO₃-based ceramics

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• 作者：Fei Liu ; Jingjing Qu ; Changlai Yuan…
• 刊名：Journal of Materials Science: Materials in Electronics
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：28
• 期：3
• 页码：3052-3059
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Optical and Electronic Materials; Characterization and Evaluation of Materials;
• 出版者：Springer US
• ISSN：1573-482X
• 卷排序：28

文摘

The effect of calcining and sintering conditions on the microwave dielectric properties of Na_0.5Sm_0.5TiO₃ (NST) solid solutions were investigated. The results showed that, after being calcined at 1100 °C for 2 h, the proposed NST system sintered at 1350 °C for 4 h exhibited a good microwave dielectric properties. Additionally, the phase assemblages, crystal structures, microstructures and microwave dielectric properties of the Na_0.5Sm_0.5[Ti_1−x(Al_0.5Ta_0.5)_x]O₃ (NSTATx, 0.1 ≤ x ≤ 0.3) and (1 − x)Na_0.5Sm_0.5TiO₃–xSm(Mg_0.5Ti_0.5)O₃ (NST–SMTx, 0.1 ≤ x ≤ 0.4) ceramics were also investigated in this work. The X-ray diffractometer results revealed that a tilted orthorhombic perovskite structure in space group Pnma was refined in the NSTATx ceramics, while the Ti₇O₁₃ phase, Sm₂Ti₂O₇ phase, and some unknown phase were detected gradually in NST–SMTx ceramics with increasing x value. Moreover, for the NSTATx solid solutions, a decreasing permittivity (ε_r) and a significant drop in quality factor (Q × f) were strongly correlated with ionic polarizability and grain sizes, respectively. On the other hand, the ε_r and Q × f values of the NST–SMTx ceramics were strongly depended on the composition and phase assemblages. Furthermore, the temperature coefficient of the resonant frequency (τ_f) of the present ceramic systems could be adjusted by the changed tilting of oxygen octahedra. An optimized microwave dielectric properties with ε_r ~ 59.4, Q × f ~ 22,200 GHz (at 4.06 GHz) and τ_f ~ 6.1 ppm/°C can be obtained in the NST–SMTx (x = 0.3) specimen sintered at 1450 °C for 4 h.