کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1492375 | 992379 | 2008 | 9 صفحه PDF | دانلود رایگان |
The dielectric properties at microwave frequencies and the microstructures of nano (α + θ)-Al2O3 ceramics were investigated. Using the high-purity nano (α + θ)-Al2O3 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 θ-phase Al2O3 addition and high-density alumina ceramics can be obtained with smaller grain size comparing to pure α-Al2O3. Relative density of sintered samples can be as high as 99.49% at 1400 °C for 8 h. The unloaded quality factors Q × f are strongly dependent on the sintering time. Further improvement of the Q × f value can be achieved by extending the sintering time to 8 h. A dielectric constant (ɛr) of 10, a high Q × f value of 634,000 GHz (measured at 14 GHz) and a temperature coefficient of resonant frequency (τf) of −39.88 ppm/°C were obtained for specimen sintered at 1400 °C for 8 h. Sintered ceramic samples were also characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).
Journal: Materials Research Bulletin - Volume 43, Issue 6, 3 June 2008, Pages 1463–1471