| Summary: | 碩士 === 國立臺北科技大學 === 材料科學與工程研究所 === 107 === In the beginning of this study, Mg4Nb2O9 (MNO) is prepared by solid state reaction method at 1300 °C for 3 hours. Then, according to the weight ratio, adding 1, 2, 4 and 8 percent of TiO2, CaTiO3 and SrTiO3 separately into MNO ceramic to form composite powder. Afterwards, using composite powder to sintered at 1200 °C and 1350 °C for 2 hours in order to prepare (1 − x) wt Mg4Nb2O9 – x wt R (R = TiO2, CaTiO3 and SrTiO3) composite ceramic. Therefore, in this research, the primary purpose of adding TiO2, CaTiO3 and SrTiO3 is to increase τf so that it can help the τf near zero, and make a good impact on dielectric properties. Indeed, after analyzing the appearance, relative density and dielectric properties of the sintered products. A dielectric constant (εr) of 12.7 and high Q f value of 13,410 GHz was obtained for 0.6 wt Mg4Nb2O9 – 0.4 wt TiO2 sintered at 1200 °C for 2 h. A εr of 12.8 and Q f value of 9,714 GHz was obtained for 0.9 wt Mg4Nb2O9 – 0.1 wt CaTiO3. A εr of 13.1 and Q f value of 51,991 GHz was obtained for 0.9 wt Mg4Nb2O9 – 0.1 wt SrTiO. Moreover, a dielectric constant (εr) of 13.4 and high Q f value of 19,792 GHz was obtained for 0.6 wt Mg4Nb2O9 – 0.4 wt TiO2 sintered at 1350 °C for 2 h. A εr of 15.2 and Q f value of 35,654 GHz was obtained for 0.2 wt Mg4Nb2O9 – 0.8 wt CaTiO3. A εr of 13.1 and Q f value of 22,891 GHz was obtained for 0.8 wt Mg4Nb2O9 – 0.2 wt SrTiO.
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