Microstructural and Microwave Dielectric Properties of Bi12GeO20 and Bi2O3‐Deficient Bi12GeO20 Ceramics |
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| Authors: | Xing‐Hua Ma Sang‐Hyo Kweon Sahn Nahm Chong‐Yun Kang Seok‐Jin Yoon Young‐Sik Kim Won‐Sang Yoon |
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| Affiliation: | 1. Department of Materials Science and Engineering, Korea University, Seoul, Korea;2. Department of Nano‐Bio‐Information‐Technology, KU‐KIST Graduate School of Converging Science and Technology, Seongbuk‐gu, Seoul, Korea;3. Electronic Materials Center, Seongbuk‐gu, Seoul, Korea;4. Department of Radio Communications Engineering, Korea University, Seoul, Korea;5. Department of Electronic Engineering, Hoseo University, Chungcheongnam‐do, Korea |
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| Abstract: | Bi12GeO20 ceramics sintered at 800°C had dense microstructures, with an average grain size of 1.5 μm, a relative permittivity (εr) of 36.97, temperature coefficient of resonance frequency (τf) of ?32.803 ppm/°C, and quality factor (Q × f) of 3137 GHz. The Bi12‐xGeO20‐1.5x ceramics were well sintered at both 800°C and 825°C, with average grain sizes exceeding 100 μm for x ≤ 1.0. However, the grain size decreased for x > 1.0 because of the Bi4Ge3O12 secondary phase that formed at the grain boundaries. Bi12‐xGeO20‐1.5x (x ≤ 1.0) ceramics showed increased Q × f values of >10 000 GHz, although the εr and τf values were similar to those of Bi12GeO20 ceramics. The increased Q × f value resulted from the increased grain size. In particular, the Bi11.6GeO19.4 ceramic sintered at 825°C for 3 h showed good microwave dielectric properties of εr = 37.81, τf = ?33.839 ppm/°C, and Q × f = 14 455 GHz. |
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| Keywords: | dielectric materials/properties grain growth grain size
LTCC
sinter/sintering |
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