| Summary: | 碩士 === 大同大學 === 材料工程學系(所) === 103 === MgZrTa2O8-based ceramics is studied for its microwave dielectric properties in this research. The study is divided into three parts. The first part is to investigate microwave dielectric properties of MgZrTa2O8. The results show that it formed a single wolframite structure. It reached highest density after sintered at 1350 ℃. Its properties were: εr = 19.45; Q×f = 54,031 GHz; τf = -36.5 ppm /℃.
The second part is to study the effects of Ca or Sr doping in MgZrTa2O8. In both kinds of doping, the sintered samples formed second phases of orthorhombic CaTa2O6 or SrTa2O6 , respectively, in addition to the main MgZrTa2O8 wolframite. The dielectric properties and the sinterability of the samples were impaired when large amounts of orthorhombic CaTa2O6 or SrTa2O6 were formed. Nevertheless, small amount of Ca doping (x=0.1) could improve the dielectric properties when orthorhombic CaTa2O6 was little.
The third part was V substitution for Ta. The heat treatment temperatures were lowered because V2O5 has low melting temperature. Due the formation of V-containing phases, the samples exhibited low sintered density or even would be broken.
The sample with the best sintered and dielectric properties was Mg0.9Ca0.1ZrTa2O8 (x = 0.1). Its properties were: density = 7.24 g/cm3; εr = 2.5; Q×f = 231,951 GHz; τf = -36.1 ppm /℃.
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