Microstructural and Microwave Dielectric Properties of Bi12GeO20 and Bi2O3‐Deficient Bi12GeO20 Ceramics. Issue 7 (5th April 2016)

• Record Type: Journal Article
• Authors: Ma, Xing‐Hua; Kweon, Sang‐Hyo; Nahm, Sahn; Kang, Chong‐Yun; Yoon, Seok‐Jin; Kim, Young‐Sik; Yoon, Won‐Sang
• Editors: Randall, C.
• Is Part Of: Journal of the American Ceramic Society. Volume 99:Issue 7(2016)
• Page Start: 2361
• Page End: 2367
• Publication Date: 2016-04-05
• Subjects: dielectric materials/properties -- grain growth -- grain size -- LTCC -- sinter/sintering; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.14240
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract : Bi12 GeO20 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 (τ f ) of −32.803 ppm/°C, and quality factor ( Q × f ) of 3137 GHz. The Bi12‐ x GeO20‐1.5 x 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 Bi4 Ge3 O12 secondary phase that formed at the grain boundaries. Bi12‐ x GeO20‐1.5 x ( x ≤ 1.0) ceramics showed increased Q × f values of >10 000 GHz, although the εr and τ f values were similar to those of Bi12 GeO20 ceramics. The increased Q × f value resulted from the increased grain size. In particular, the Bi11.6 GeO19.4 ceramic sintered at 825°C for 3 h showed good microwave dielectric properties of εr = 37.81, τ f = −33.839 ppm/°C, and Q × f = 14 455 GHz.