Ba2Ti9O20微波介電陶瓷之製備及其微波特性之研究

Preparation and Investigation of Ba2Ti9O20 Dielectric Ceramics and its Microwave Properties

鍾明蓉(Ming-Rung Chung)

指導教授 ： 王宏文

中原大學/理學院/化學研究所/碩士(2001年)

https://doi.org/10.6840/cycu200100236

摘要

摘 要

高反應的粉末分別以EDTA化學法、共沉法及氧化物混合法製備，以進一步了解三種方式獲得粉末的均勻程度。其中EDTA酸膠化法燒結在1150℃/3小時就可獲得單一純相的Ba2Ti9O20，而共沉法燒結在1300℃/2小時卻獲得Ba2Ti9O20和BaTi4O9兩個相，若以氧化混合法燒結在1300℃/2小時獲得的相以BaTi4O9為主而Ba2Ti9O20為次之。由以上結果可推知化學成份的均勻程度分為﹕EDTA化學法>共沉法>氧化物混合法。

基於EDTA化學法獲得的成份最均勻，於是進一步了解EDTA化學法製程之變數。使用EDTA化學法成份均勻且活性高的粉末，燒結在1250℃/3小時可獲得單一純相Ba2Ti9O20及高達 98%緻密程度的陶瓷。取製程中加入乙二醇的鍛燒粉末，經燒結在1200℃可獲得單一純相之Ba2Ti9O20。比較EDTA、EDTA加EG及EDTA加球磨三種粉得知粉末凝聚的程度也會影響單一相Ba2Ti9O20之生成。本研究獲得最佳的微波特性為﹕εr =38.8 ; Q = 4000 ( 7 GHz) ; τf = 1.5 ppm /℃。

以氧化物混合法製備Ba2Ti9O20並添加Nd2O3、CaO、Al2O3等添加物，添加2 mole% Nd或1 mole% Ca燒結緻密程度可達 97%，但是添加Al燒結密度有些許下降。添加物無法有效的獲得單一純相Ba2Ti9O20仍然有小量BaTi4O9二次相的出現。添加Nd2O3、CaO、Al2O3對Ba2Ti9O20陶瓷體的微波特性有下列變化: 添加量越多則共振頻率的溫度係數(τf)和介電常數
(εr)增加而品質係數(Q factor)則降低。

關鍵字

相生成 ； 化學法 ； 共沉法 ； 微波特性 ； 溶液-凝膠 ； 介電陶瓷 ； 燒結

並列摘要

Abstract

Reactive powders have been prepared by the EDTA-gel method, co-precipitation method and mix-oxide method. The degree of homogeneity of compositions is estimated as EDTA-gel > co-precipitation > mixed-oxide. The merits of EDTA-gel method can be realized by comparing the phase formation with those of other methods. Single Ba2Ti9O20 phase were readily obtained by EDTA-gel method at a sintering condition as low as 1150℃ for 3 hours, while other method result in BaTi4O9 second phase. In additional, Single Ba2Ti9O20 phase and l98% dense ceramic were readily obtained by sintering the fine powders at 1250℃ for 3 hours. The additional of ethylene glycol in the EDTA solution facilitates the formation of single Ba2Ti9O20 phase after sintering at 1200℃. From the powders derived from EDTA, EDTA-EG (add ethylene glycol), EDTA-BM (ball-milled), it is suggested that the degree of hard agglomeration of the powders also affects the formation of Ba2Ti9O20 phase. The best microwave characteristics for Ba2Ti9O20 of present study are: εr-=38.8;Q = 4000 at 7GHz, and τf = 1.5 ppm/℃.

Ba2Ti9O20 doped with Nd,Ca and Al are also prepared from carbonates and oxides. The ceramics with densities exceeding 97% of theoretical value are made with 2 mole% Nd or 1 mole% Ca, while doping with Al decrease the densities. The additions do not obtain Single Ba2Ti9O20 phase but with a small second phase BaTi4O9. The effect of Nd, Ca and Al doping on the dielectric properties of Ba2Ti9O20 ceramic has been investigated at microwave frequency and low frequency. The dielectric constantεr and the temperature coefficients of frequency τf increases as the dopants increase, and an decrease in the Q values are also abserved.

並列關鍵字

Dielectric Resonator ； Ceramic ； Ba2Ti9O20 ； Microwave Properties ； EDTA method ； Dopant

參考文獻

27. Ekkehart Tillmanns and Wolfgang Hofmeister, "Crystal Structure of the

12.Shoichiro Nomura, Keiichiro Tomaya and Kumiko Kaneta,"Effect of Mn

Compound with Temperature-Stable High Permittivity and Low Microwave

Loss", J. Am. Ceram. Soc.,57 (10 ), October 1974, p.450 ~ 453.

Microwave Dielectric Resonator", J. Am. Ceram. Soc., 58 (9-10), 1975,