| Summary: | 碩士 === 崑山科技大學 === 電子工程研究所 === 93 === Columbite ZnNb2O6 (ZN) and MgNb2O6 (MN) ceramics produced by a reaction-sintering process were investigated. The mixture of raw materials was pressed and sintered into ceramics without any calcination stage involved. Columbite ZN and MN phases could be obtained after 2h and 4h sintered at 1050 – 1350oC. A density value 5.57 g/cm3 (99% of the theoretical value) was obtained for 4h sintering at 1150oC in ZN pellets. The sintering temperature can be effectively reduced to 1000oC in ZN ceramics with 2wt% CuO additions. Mg0.652Nb0.598O2.25 and Mg0.66Nb11.33O29 phases were also found in the sintered MN ceramics. A density value 4.85 g/cm3 (97.1% of the theoretical value) was obtained for 2h sintering at 1250oC in MN pellets. The microwave dielectric properties єr~23.5, Q×f~61916GHz , τf ~-50ppm/oC and єr~17.3,
Q×f~24886GHz , τf ~-78ppm/oC were obtained in ZN and MN, respectively. As TiO2 was added into ZN, τf values approach 0 ppm/oC could be found in 0.42ZnNb2O6－0.58TiO2. Good dielectric properties єr~38.1, Qxf~21676GHz and τf ~
-10ppm/oC were obtained in 0.42ZnNb2O6－0.58TiO2 ceramics sintered at 1200oC for 2h.
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