Preparation of A4Nb2O9 (A=Mg,Ni) Microwave Dielectric Ceramics by Reaction-Sintering Process

• Main Authors: Zong-Sian Tsai, 蔡宗憲
• Other Authors: Yi-Cheng Liou
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/92703932896006529462

碩士 === 崑山科技大學 === 電子工程研究所 === 100 === Microwave dielectric ceramics Mg4Nb2O9 (MN) and Ni4Nb2O9 (NN) prepared by a reaction-sintering process were investigated. The mixture of raw materials was pressed and sintered into ceramics without any calcination stage involved. CaTiO3 and SrTiO3 were used to obtain MN with near-zero τf. Single-phase MN ceramics were obtained by adding excess Mg(OH)2. Mg4Nb2O9 along with minor MgNb2O6 were found in 2h sintering MN. Mg0.652Nb0.598O2.25 phase appeared at 1200oC sintering. The optimum density 4.26g/cm3 and shrinkage 21.92% were obtained at 1300oC/6h sintering. εr＝10.74,Qxf＝231,368GHz(12.18GHz),τf＝－40.24 ppm/oC were obtained at 1170oC/2h. MNCT and MNST ceramics were composed of Mg4Nb2O9 with CaTiO3 and SrTiO3,respectively. MNCT with τf＝－6.55 and MNST with τf＝－18.21ppm/oC were obtained. MNH5 ceramics with single-phase Mg4Nb2O9 could be obtained and no second phase was detected. The optimum density 4.14g/cm3 and shrinkage 23.67% were obtained at 1300oC/2h sintering. εr＝10.37,Qxf ＝203,620GHz (12.68GHz),τf＝－20.81 ppm/oC were obtained at 1170oC/4h. NiNb2O6 along with NiO formed at 1170 to 1300oC/2h sintering,NN. Ni4Nb2O9 phase appeared at 1300oC sintering and Ni4Nb2O9 became major phase at sintering temperature >1300 oC. The optimum density 5.71g/cm3 and shrinkage 13.97% were obtained. εr＝13.23,Qxf＝21,085GHz (10.53GHz),τf＝－13.58 ppm/oC were obtained at 1350oC/2h sintering. With a heating rate and cooling rate of 30oC/min, NN of pure Ni4Nb2O9 could be obtained at 1300oC/2h sintering.