Effect of NdAlO₃ on microstructure, dielectric properties and temperature-stable mechanism of (Sr, Ca, Nd)TiO₃ ceramics at microwave frequency

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• 作者：Jingjing Qu ; Delong Huang ; Xing Wei ; Fei Liu…
• 刊名：Journal of Materials Science: Materials in Electronics
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：27
• 期：10
• 页码：11110-11117
• 全文大小：1,647 KB
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Chemistry
  Optical and Electronic Materials
  Characterization and Evaluation Materials
  
• 出版者：Springer New York
• ISSN：1573-482X
• 卷排序：27

文摘

Microwave dielectric ceramics (1 − x)(Sr_0.3Ca_0.427Nd_0.182)TiO₃–xNdAlO₃ (abbreviated as SCNTAx hereafter, 0.1 ≤ x ≤ 0.4) were prepared by conventional mixed oxide route, and their phase composition, microstructure and microwave dielectric properties were investigated as a function of the x value and sintering temperatures. A single tilted orthorhombic perovskite structure in space group Pnma was refined in the studied composition range. For microware dielectric properties, the decreasing relative permittivity was strongly affected by the ionic polarizability of Nd3+ and Al3+ in SCNTAx ceramic systems. Also, the quality factor of SCNTAx solid solution had strongly depended on apparent densities and average grain sizes. As expected, the promising ceramic of SCNTAx (x = 0.25) sintered at 1520 °C for 4 h was found to possess good microwave dielectric properties: a relative permittivity (ε_r) of 55.6, a quality factor (Q × f) of 25,600 GHz (at 4.249 GHz) and a temperature coefficient of resonant frequency (τ_f) of 6.7 ppm/°C. Especially, the τ_f values of SCNTAx ceramics were not strongly depended on tolerance factor (t) with increasing of the NdAlO₃ content, while these τ_f values were essentially correlated with the B-site bond valence and octahedral tilting. Wherein, either decreasing the B-site bond valence or increasing the octahedral tiltings (θ and φ) led to a decrease in τ_f value for the present ceramics.