Effect of partial nitridation on the dielectric constant of A₅Ta₄O₁₅ (A=Sr, Ba)

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• 作者：Hyeon-Dong Han ; Jung-Mi Kim ; Young-Il Kim ; ^{yikim@ynu.ac.kr" class="auth_mail" title="E-mail the corresponding author}
• 关键词：C. Dielectric properties ; D. Nitrides ; D. Tantalates
• 刊名：Ceramics International
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：43
• 期：1
• 页码：766-770
• 全文大小：761 K

文摘

The anion lattice of dielectric oxides A₅Ta₄O₁₅ (A=Sr, Ba) were modified using a mild ammonolysis treatment, which led to A₅Ta₄O_15–3xN_2x. N-doping was examined by varying the ammonolysis temperature and time in the ranges of 1023–1173 K and 2–20 h, respectively. Using sintered ceramics of A₅Ta₄O₁₅, N-doping could be achieved up to 2x≈0.4 for both Sr₅Ta₄O_15–3xN_2x and Ba₅Ta₄O_15–3xN_2x. The nitridation of A₅Ta₄O₁₅ was not accompanied by a significant change in the crystal structure but a substantial evolution of the electronic structure was observed, as indicated by the marked shift in the band gap. Capacitance measurements revealed a ≈50% increase in the dielectric constants (κ) of A₅Ta₄O₁₅ upon N-doping. At 100 kHz and 295 K, κ was measured to be 37 for Sr₅Ta₄O₁₅, 54 for Sr₅Ta₄O_14.4N_0.4, 26 for Ba₅Ta₄O₁₅, and 43 for Ba₅Ta₄O_14.4N_0.4. All the Sr₅Ta₄O₁₅, Ba₅Ta₄O₁₅, and Ba₅Ta₄O_14.4N_0.4 displayed temperature-stable dielectric behavior in the range, 30–450 K. On the other hand, Sr₅Ta₄O_14.4N_0.4 exhibited a rapid increase in κ with increasing temperature, suggesting strong lattice anharmonicity.