Microwave dielectric properties and thermally stimulated relaxations of Ba_0.6Sr_0.4La₄Ti₄O₁₅−TiO₂ composite ceramics by flowing oxygen sintering

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• 作者：Xiaohua Zhang ; Jie Zhang ; Yao Zhang…
• 刊名：Journal of Materials Science: Materials in Electronics
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：28
• 期：4
• 页码：3400-3406
• 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

Phase structure, sintering behavior, microwave dielectric properties and thermally stimulated relaxations of the 0.93Ba_0.6Sr_0.4La₄Ti₄O₁₅−0.07TiO₂ composite ceramics were investigated through using flowing oxygen atmosphere sintering. Ba_0.6Sr_0.4La₄Ti₄O₁₅ (BSLT) sintered at 1500 °C possesses microwave dielectric properties of ε_r = 44, Q × f = 45,000 GHz and τ_f = −7.5 ppm/°C. Rutile TiO₂ with ε_r = 105, Q × f = 46,000 GHz, τ_f = +465 ppm/°C was combined with the BSLT to compensate the negative τ_f value in current research. XRD reveals that the ceramic samples possess a hexagonal perovskite structure and a secondary phase of TiO_2−δ. The 0.93BSLT−0.07TiO₂ compounds sintered in flowing oxygen exhibit small grain sizes and some pores, which are less compactly sintered compared with the ones sintered in air. The densification, grain growth and microwave dielectric properties of 0.93BSLT−0.07TiO₂ have a clear dependence on sintering temperature. The 0.93BSLT−0.07TiO₂ composite ceramics sintered at 1500 °C possess good microwave dielectric properties: ε_r = 47.2, Q × f = 32,400 GHz and τ_f = −3.3 ppm/°C. The extrinsic loss mechanism associated with defects was explored by relying on thermally stimulated depolarization current (TSDC) measurement. It can be manifested that TSDC relaxations are mostly derived from oxygen vacancies and TSDC spectra are evidently affected by the sintering temperature.