臺灣博碩士論文加值系統

由於微波介電共振器具有適當的介電係數、低的共振頻率溫度係數和低介電損失，使得微波介電共振器被廣泛的應用在微波通訊元件上。本實驗探討摻雜2wt%、4wt%、6wt%和8wt% MgO-CaO-SiO2-Al2O3 (MCAS) 玻璃之 (1-x)Al2O3 - xTiO2 (x=0.08, 0.12, 0.16)介電共振器陶瓷材料的晶相和微波介電特性。由於Al2O3之共振頻率溫度係數為負(τf = -55 ppm/℃)而TiO2之共振頻率溫度係數為正(τf = +450 ppm/℃)，所以希望以混合粉末的方式來製作τf ~0 ppm/℃之陶瓷。另外，本研究亦以不同MCAS玻璃含量液相燒結促進劑，探討其降低燒結溫度之效果。
在摻雜MCAS之 (1-x)Al2O3 - xTiO2 系統中，Al2TiO5 相大約出現在1250℃，在TiO2相耗盡前Al2TiO5相強度隨燒結溫度和MCAS玻璃增加而增加。隨著燒結溫度增加，在1250℃時介電係數和Q×f 值到達最大值，而τf 值可由正轉換到負。在摻雜2wt% MCAS之 88mol%Al2O3 - 12mol%TiO2 組成中，燒結溫度在1300℃時能得到最佳的τf 值(—0.6 ppm/℃)。MCAS的含量、TiO2的含量和燒結溫度的改變，會得到不同微波介電特性的陶瓷材料。 在摻雜MCAS玻璃之(1-x)Al2O3 - xTiO2 系統中，可得到εr=7~9.5、Q×f=6500~1100和τf= -60 到 +40ppm/℃等不同的微波介電特性。因此我們可藉由調變不同的MCAS含量、TiO2含量和燒結溫度來得到最佳特性的微波介電陶瓷材料。

Microwave dielectric resonators (DRs) are being widely used in microwave telecommunication devices owing to their excellent characteristics of suitable dielectric constant, good temperature stability, and low dielectric loss. In this study, the crystalline phase and the microwave dielectric properties of the (1-x)Al2O3 - xTiO2 (x=0.08, 0.12, 0.16) compositions with 2wt%, 4wt%, 6wt%, and 8wt% MgO-CaO-Al2O3-SiO2 (MCAS) glass addition have been investigated. By combining the material Al2O3 with negative temperature coefficient of the resonant frequency (τf = -55 ppm/℃) and the material TiO2 with positive τf value (τf = +450 ppm/℃), it is desired to produce the ceramics with τf ~0 ppm/℃. The MCAS is used as liquid-phase sintering aid to lower down the sintering temperature.
In the MCAS-doped (1-x)Al2O3 - xTiO2 system, the Al2TiO5 phase starts to appear at about 1250℃, and then the crystalline intensity of Al2TiO5 phase increases with the increase of sintering temperatures and MCAS glass content, until the temperatures that TiO2 is consumed. As the sintering temperature increases, the maximum dielectric constants and Q×f values can be obtained at 1250℃, and the τf values shift from positive to negative. The optimum τf value of —0.6 ppm/℃ exists in the 88mol%Al2O3 - 12mol%TiO2 composition with 2wt% MCAS addition and sintering temperature of 1300℃. The MCAS content, TiO2 content, and sintering temperature will result in the variation of microwave dielectric properties. In this study, MCAS-doped (1-x)Al2O3 - xTiO2 system exhibits the microwave dielectric properties of： εr=7~9.5, Q×f=6500~11000, and τf = -60 to +40ppm/℃. By adjusting the MCAS content, TiO2 content, and sintering temperatures, ceramics with good microwave properties can be obtained in the MCAS-doped (1-x)Al2O3 - xTiO2 system.

Contents
Page
Chapter 1 Introduction………………………………………………………………....1
Chapter 2 Theory……………………………………………………………….……...4
2-1 Theory of liquid phase sintering…………………………………….……….4
2-2 Theory of microwave dielectric properties…………………………….….…6
2-3 Theory and analysis of dielectric resonator…………………………..……...9
Chapter 3 Experimental procedures..…………………………………….………..…12
3-1 Sample preparation……………………………………………………...….12
3-2 Measurement method of microwave dielectric properties…...……………..13
(Ⅰ) Calculation of dielectric constant……………………………………...13
(Ⅱ) Measurement of Q values……………………………………………14
(Ⅲ) Measurement ofτf values…………………………………………16
Chapter 4 Results and discussion……………………………………………….……18
4-1 X-Ray diffraction (XRD) analysis……………………………………..…...18
4-2 SEM analysis………………………………………………………………..19
4-3 Analysis of density………………………………………………………….20
4-4 Analysis of microwave dielectric properties………………………………..21
(Ⅰ) Dielectric constant (εr)………………………………………………..21
(Ⅱ) Q×f values…………………………………………………………….23
(Ⅲ) Temperature coefficient of resonant frequency (τf)………………...24
Chapter 5 Conclusion.……………………………………………………………..…27
References………………………………………………………………………..…29

References
[1]Wolfram Wersing, “Microwave ceramics for resonators and filters,” Current Opinion in Solis State & Materials Science, 1 (1996) pp.715-731.
[2]Kishk A.A., Lttipiboon A., Antar Ymm, Cuhaci M., “Slot excitation of the dielectric disk radiator,” IEEE Trans. Antennas propagate, 43 (1995) pp.198-201.
[3]Shum SM, Luk KM, “Stacked annular ring dielectric resonator antenna excited by axi-symmetric coaxial probe,” IEEE Trans. Antennas propagate, 43(1995) pp.889-892.
[4]吳朗, ”電工材料” 滄海書局 (1998) pp.321.
[5]Neil McN. Alford, Stuart J. Penn, “Sintered alumina with low dielectric loss,” Journal of Applied Phys., 80 (10) (1996) pp. 5895-5898.
[6]Alan Templetin, Xiaoru Wang, Stuart J. Penn, Stephen J. Webb, Lesley F. Cohen, Neil McN. Alford, “Microwave dielectric loss of titanium oxide,” Journal of the American Ceramic Society, 83 (2000) [1] pp.95-100.
[7]Chien-Min Cheng, Cheng-Fu Yang, Shi-Hong Lo, Tseung-Yuen Tseng, “Sintering BaTi4O9/Ba2Ti9O20-based ceramics by glass addition,” Journal of the European Ceramic Society, 20(2000) pp.1061-1067.
[8]Cheng-Fu Yang, “The mechanical properties of MgO-CaO-SiO2-Al2O3 composite glass,” Materials Science and Engineering C, 4(1997) pp.315-319.
[9]Randalll M. German, “Liquid Phase Sintering,” Plenum Press, New York (1985).
[10]汪建民,“陶瓷技術手冊（上）,” 全華科技 (1999) pp. 404.
[11]William D. Callister JR., “Materials Science and Engineering An Introduction,” 5th ed., John Wiley & Sons INC, New York (2000) pp. 643.
[12]F.C Brown, “The Physics of Solids,”2th ed., W.B. Saunders, New York (1985).
[13]B.D. Silvermann, “Microwave absorption in cubic strontium titanate,” Physics reverend, 125 (1962) pp.1921-1930.
[14]D.K. Cheng, “Field and Wave Electromagnetics,” Addison Wesley, New York (1989).
[15]D. Kajfez, A.W. Glisson, J James, “Computed modal field distributions for isolated dielectric resonators,” IEEE Trans. on Microwave Theory and Techniques, MTT-32 (1984) pp.1609-1616.
[16]Cheng-Fu Yang, “The microwave characteristics of glass-BaTi4O9 ceramics,” Japanese Journal of Applied Physics, 38 (1999) pp.3576-3579.
[17]B.W. Hakki, P.D Coleman, “A dielectric resonator method of measuring inductive capacities in the millimeter range,” IEEE Trans. on Microwave Theory Tech., MTT-8 (1960) pp.402-410.
[18]William E. Courtney, “Analysis and evaluation of a method of measuring the complex permittivity and permeability of microwave insulators,” IEEE Trans. on Microwave Theory and Techniques, MTT-18 No.8 (1970) pp.476-485.
[19]P. Wheless, D. Kajfez,” The use of higher resonant modes in measuring the dielectric constant of dielectric resonators,” IEEE MTT-S Symposium Dig., (1985) pp.473-476.
[20]Yoshio Kobayashi, S. Tanaka,” Resonant modes of a dielectric rod resonator short-circuited at both ends by parallel conducting plates,” IEEE Trans. on Microwave Theory and Techniques, MTT-28 No.10 (1980) pp.1077-1085.
[21]Darko Kajfez, Pierre Guillon, “ Dielectric Resonators,” Artech House, Washington (1986) pp.339.
[22]Yoshio Kobayashi, M. Katoh, “Microwave measurement of dielectric properties of low-loss materials by the dielectric rod resonator method,” IEEE Trans. on Microwave Theory and Techniques, MTT-33 (1985) pp.586-592.
[23]Cohn S.B., Kelly K.C.,” Microwave measurement of high-dielectric constant materials,” IEEE Trans. on Microwave Theory and Techniques, MTT-14 (1966) pp.406-410.
[24]Fulrath Pask, “ Ceramic Microsructures,” Plenum Press, New York (1968).
[25]1999 JCPDS-International Centre for Diffraction Data (86-1550, 26-0040, 21-1276, 82-1399)
[26]Hiromichi Okamura, Eric A. Barringer, H. Kent Bowen, “Preparation and sintering of narrow-sized Al2O3-TiO2 composite powders,” Journal of Materials Science, 24(1989) pp.1867-1880.
[27]Cheng-Fu Yang, ”The sintering characteristics of MgO-CaO-SiO2-Al2O3 composite powder made by Sol-Gel method,” Ceramics International, 24 (1998) pp.243-247
[28]Wersing W., “High frequency ceramic dielectrics and their application for microwave components,” Electronic Ceramics (1991) pp.67-119.
[29]R. Vila, M. Gonzalez, J. Molla. Ibarra, “ Dielectric spectroscopy of alumina ceramics over a wide frequency range,” Journal of Nuclear Materials, 253 (1998) pp.141-148.