The Sintering and Microwave Dielectric Characteristics of ... - SEE

saturated value of –0.7 ppm/ o C as 1450 o C is used as sintering temperature. Although the maximumQ×f values of MgTa 1.5 Nb 0.5 O 6 ceramics are somewhat lower than that of MgNbO 6 ceramics,however, the τ f value is largely improved is this study. It reveals the potential applications ofMgTa 1.5 Nb 0.5 O 6 as microwave devices.4. ConclusionFor the saturated microwave dielectric characteristics of MgTa 1.5 Nb 0.5 O 6 ceramics, the ε r valuesare smaller than those of MgTa 2 O 6 ceramics but larger than those of MgNb 2 O 6 ceramics. The Q×fvalues of MgTa 1.5 Nb 0.5 O 6 ceramics are smaller than those of MgTa 2 O 6 and MgNb 2 O 6 ceramics.However, the τ f values of MgTa 1.5 Nb 0.5 O 6 ceramics are more close to 0 ppm/ o C than those ofMgTa 2 O 6 and MgNb 2 O 6 ceramics are. In this study, the MgTa 1.5 Nb 0.5 O 6 ceramics sintered at 1450 o Cwill reveal the optimum microwave dielectric characteristics of ε r =27.9, Q×f=33100 GHZ, and τ f =–0.7 ppm/ o C.References[1] S. Kucheiko, J. W.Choi, H. J.Kim and H. J. Jung: J.Am.Ceram.Soc. 79 (1996) 2739.[2] K. Ezaki, Y. Baba, H. Takhashi, K. Shibata and S. Nakano: Jpn.J.Appl.Phys. 32 (1993) 4319.[3] Y.C. Chen, P.S. Cheng, C.F Yang and W.C. Tzou: J.Mater.Sci.Let. 20 (2001) 1169.[4] A. Kan, H. Ogawa and H. Ohsato: J. Alloys and Compounds 337 (2002) 303.[5] H. J. Lee, I. T. Kim and K. S. Hong: Jpn.J.Appl.Phys.Let. 36 (1997) 1318.[6] B. W. Hakki and P. D. Coleman: IRE. Trans. MTT, 1960, 8, 402-410.[7] W. E. Courtney: IRE. Trans. MTT, 1985, 18, 476-485.[8] JCPDS card no.84-1679 and 88-0708, 1999 JCPDS International Center for Diffraction DataFormerly by the Joint Committee on Power Diffraction Standards.Table I: Microwave dielectric properties of MgTa 2 O 6 and MgNb 2 O 6 ceramics.Material Sintering temperature ( o C) ε r Q×f (GHz) τ f (ppm/ o C)MgTa 2 O 6 1400 25.2 28500 22.4MgTa 2 O 6 1450 28.9 44300 27.1MgTa 2 O 6 1500 30.5 56900 28.3MgTa 2 O 6 1550 30.6 58200 28.5MgNb 2 O 6 1300 15.7 34100 –78MgNb 2 O 6 1350 20.5 66500 –69.1MgNb 2 O 6 1400 21.7 89900 –68.5MgNb 2 O 6 1450 21.8 91500 –68.34

Fig. 1 The microstructures of MgTa 1.5 Nb 0.5 O 6 ceramics sintered at different temperatures.(a) 1300 o C, (b) 1350 o C, and (c) 1400 o C.(311)(400)(111)(020)(220)(002)(021)(202)(600)(221)(321) (420)(312)(421) (402)(022)(620)(711)(131)(231)(621)(422)1400 o C1350 o C1300 o C20 30 40 50 602θ valueFig. 2 The X-ray patterns of MgTa 1.5 Nb 0.5 O 6 ceramics sintered at different temperatures.5

density(g/cm 3 )5.85.4dielectric constant5.02824201300 1350 1400 1450sintering temperature( o C)Fig. 3 The density and the dielectric constants of MgTa 1.5 Nb 0.5 O 6 ceramics sintered at differenttemperatures.τ fvalue(ppm/ o C)-1.0-3.0321quality value(x10 4 )-5.01300 1350 1400 1450sintering temperature( o C)Fig. 4 The quality values and the temperature coefficients of resonant frequency of MgTa 1.5 Nb 0.5 O 6ceramics sintered at different temperatures.6