Microstructural and Microwave Dielectric Properties of Bi12GeO20 and Bi2O3-Deficient Bi12GeO20 Ceramics

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...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 2016-07, Vol.99 (7), p.2361-2367
Main Authors: Ma, Xing-Hua, Kweon, Sang-Hyo, Nahm, Sahn, Kang, Chong-Yun, Yoon, Seok-Jin, Kim, Young-Sik, Yoon, Won-Sang
Format: Article
Language:English
Subjects:
Alloys
Ceramics
Coefficients
dielectric materials/properties
Dielectric properties
Grain boundaries
grain growth
Grain size
LTCC
Microstructure
Microwaves
Permittivity
Q factors
sinter/sintering
Sintering
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Summary: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.
ISSN:0002-7820
1551-2916
DOI:10.1111/jace.14240