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Nb-Doped 0.9BaTiO3–0.1(Bi0.5Na0.5)TiO3 Ceramics with Stable Dielectric Properties at High Temperature

Authors

  • Guofeng Yao,

    1. State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing, China
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  • Xiaohui Wang,

    Corresponding author
    • State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing, China
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  • Yunyi Wu,

    1. State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing, China
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  • Longtu Li

    1. State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing, China
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  • This work was supported by the National Science Fund for Distinguished Young Scholars (Grant No. 50625204), the National Natural Science Fund for Creative Research Groups (Grant No. 50921061), and the Ministry of Science and Technology of China through National Basic Research Program of China (973 Program, Grant No. 2009CB623301) and through National High Technology Research and Development Program of China (863 Program, Grant No. 2006AA03Z428), and the Outstanding Tutors for Doctoral Dissertations of S&T Project in Beijing (Grant No. YB20081000302), and Tsinghua University Initiative Scientific Research Program.

Author to whom correspondence should be addressed. e-mail: wxh@tsinghua.edu.cn

Abstract

Nb-doped 0.9BaTiO3–0.1Bi0.5Na0.5TiO3 (0.9BT–0.1BNT) ceramics were prepared by conventional solid-state method. The dielectric and the structural properties were investigated. It was found that the temperature–capacitance characteristics greatly depended on Nb2O5 content. With the addition of 2.0 mol% Nb2O5, 0.9BT–0.1BNT ceramic sample could satisfy the EIA X9R specification. This material was promising for high-temperature MLCC application. Microstructure element distribution was studied using TEM and EDS. The Bi and Na were almost homogeneously distributed except grain-boundary segregation of Bi. The Nb exhibited a nonuniform distribution from the grain boundary to the interior, showing the simultaneous presence of Nb-rich and Nb-poor regions. Such microheterogeneity gave rise to the temperature stability of permittivity. The solution-precipitation mechanism was introduced to elucidate the evolution of microstructures. Degradation and recovery of insulation resistance were observed under a dc bias at 200°C, which was attributed to the electromigration and diffusion of Na+.

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