| Summary: | 碩士 === 國立臺北科技大學 === 材料科學與工程研究所 === 95 === Calcium-Titanate ceramics exhibit a combination of high permittivity ( εr ) about 170, and high Q×f = 6000 ~ 12,000 GHz, which make it a suitable candidate for microwave dielectric materials. The major disadvantage of CaTiO3 is its ultra high postive temperature coefficient of frequency ( τf ), it will discourages the development, hence have to blend to compensate with a ceramics with negative τf-value. The ReAlO3 and ReGaO3 with the pervoskite structure are doped in CaTiO3 by forming solid solution in this study. ReAlO3 and ReGaO3 with permittivity about 15-25, Q×f value from 50,000 to 100,000 GHz, and with a small negative τf from -30 to -70 ppm/oC. For the reason that is chosed to compensate for CaTiO3 with the high τf value. In the results, the behaviour on densification, phase assemblage, microstructure characteristics, and analysis on dielectric properties were be investigated.
In the result of the study, the solid solutions ceramics prepared with different amount mol% NdAlO3 added in CaTiO3 via the solid-state reaction. Ceramics based on the 0.7CaTiO3+0.3NdAlO3 exhibits single phase, and with εr = 48, Q×f ~ 40,000, and τf = 16.03 ppm/oC, The LaGaO3 was chosen to carried out with high Q×f ~ 97,000. When the 36 mol% LaGaO3 added in CaTiO3 ceramics exhibits εr = 49, Q×f ~ 44,000, and τf = 14.6 ppm/oC. With the slower cooling rate of 0.5oC/min is useful for increasing Q×f values. The 0.7CaTiO3+0.3NdAlO3 ceramics with εr = 45.6, Q×f ~ 43,000, and τf near zero about 2 ppm/oC
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