Microwave dielectric properties and sintering behavior of nano-scaled ({alpha} + {theta})-Al{sub 2}O{sub 3} ceramics
Journal Article
·
· Materials Research Bulletin
- Department of Electrical Engineering, National Cheng Kung University, Tainan, Taiwan (China)
- Department of Resource Engineering, National Cheng Kung University, Tainan, Taiwan (China)
The dielectric properties at microwave frequencies and the microstructures of nano ({alpha} + {theta})-Al{sub 2}O{sub 3} ceramics were investigated. Using the high-purity nano ({alpha} + {theta})-Al{sub 2}O{sub 3} powders can effectively increase the value of the quality factor and lower the sintering temperature of the ceramic samples. Grain growth can be limited with {theta}-phase Al{sub 2}O{sub 3} addition and high-density alumina ceramics can be obtained with smaller grain size comparing to pure {alpha}-Al{sub 2}O{sub 3}. Relative density of sintered samples can be as high as 99.49% at 1400 deg. C for 8 h. The unloaded quality factors Q x f are strongly dependent on the sintering time. Further improvement of the Q x f value can be achieved by extending the sintering time to 8 h. A dielectric constant ({epsilon}{sub r}) of 10, a high Q x f value of 634,000 GHz (measured at 14 GHz) and a temperature coefficient of resonant frequency ({tau}{sub f}) of -39.88 ppm/deg. C were obtained for specimen sintered at 1400 deg. C for 8 h. Sintered ceramic samples were also characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM)
- OSTI ID:
- 21144021
- Journal Information:
- Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 6 Vol. 43; ISSN MRBUAC; ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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