摘要
　　菫青石因具有低介電常數、低熱膨脹係數、高電阻係數、高熱傳導率、高機械強度與極佳的抗熱震等優異的特性，故其用途非常廣泛，除了傳統用途如汽車用燃氣輪機的熱交換器，排氣淨化用觸媒載體等，亦極適合作為積體電路基板材料 (Integrated Circuit Substrates)。
　　菫青石 (Cordierite) 是MgO-Al2O3-SiO2三成份系統中的化合物，其計量組成為2MgO．2Al2O3．5SiO2。本研究將MgCl2、AlCl3及TEOS與酒精混合配製成[Mg2+] = 0.1 M、[Al3+] = 0.2 M及[Si4+] = 0.25 M之溶液並混合，再將1 M 之NH4OH以5 ml/min之速率滴入混合液中進行溶膠凝膠反應，合成菫青石之前導物粉末，並以此前導物製備菫青石粉末及燒結體。探討：(1) 溶液pH值對共沉結果及煆燒後粉末結晶相的影響；(2) 煆燒條件對菫青石粉末粒徑及燒結體的影響；(3) 燒結助劑對燒結體結晶相及對其熱電性質的影響。
根據實驗結果發現共沉pH值在9以上，反應較為完全，殘留在濾液中Mg2+、Al3+與Si4+含量大幅降低。以1400℃持溫3小時煆燒，pH 9 ~ 10之共沉粉末全部為α-菫青石。pH 9之共沉粉末以500℃持溫3小時煆燒，顆粒粒徑為18.9 nm。
　　比較低溫與高溫煆燒所製備之燒結體，發現前者較緻密，且其緻密化發生的溫度比高溫者低約200℃，顯示低溫煆燒對後續的燒結行為有較佳的結果。
　　本研究以氧化鉍 (Bi2O3) 作為燒結助劑，發現氧化鉍不但可有效降低α-菫青石結晶相析出的溫度，並可降低燒結緻密溫度。以870 ~ 970℃持溫8小時燒結，燒結體之氧化鉍添加量為15 ~ 20 wt%。熱膨脹係數為17~20 x 10-7 /℃，與矽之熱膨脹係數相配合。燒結體若無添加氧化鉍，其絕緣電阻係數比添加者低。隨氧化鉍添加量之增加，絕緣電阻係數有增加然後穩定的趨勢。本研究中所測得最佳電阻係數為4 x 1011Ωcm。
　　實驗結果顯示利用氧化鉍為燒結助劑，在低於1000℃的燒結溫度下得到一緻密度和熱電性質皆相當良好的燒結體。所測得最高品質因子可達10,000 ~ 20,000 (1 MHz)，且於高頻率 (18 GHz) 仍具有404 ~ 620的品質因子，屬於相當優良的品質因子。

Abstract
　　Cordierite has low dielectric constant, low thermal expansion coefficient, high resistivity, high conductivity and good mechanical strength; it is mainly used in the fabrication of catalytic converter honeycomb supports used in automobiles, self-cleaning ovens and industrial heat exchangers for turbines. Besides, cordierite is expected to have great potential as a substrate material for integrated circuit board replacing alumina, which has a relatively low dielectric constant (~5) at the high frequency region.
Cordierite is a ternary compound of the MgO-Al2O3-SiO2 system, with the stoichiometric composition of 2MgO．2Al2O3．5SiO2. A sol-gel process was utilized to prepare low-temperature sinterable ceramics with a stoichiometric cordierite composition, in which Bi2O3 additives were incorporated to control the crystallization process and lowering the sintering temperature
In this study, ultrafine powders were precipitated by titrating NH4OH into the aqueous solution of MgCl2, AlCl3, TEOS and alcohol. The suitable pH value would be 9 and the above for the reaction to be completed. By calcining the powders, α-cordierite precursor was obtained.
　　Comparing the ceramic bulks prepared by low temperature calcinations (500℃) and high temperature calcinations (1400℃), the previous sample has denser structure, which means that low temperature calcinations has a better influence in sintering behavior.
The highest quality factors found in this study were 10,000 ~ 20,000 in 1 MHz, and 404 ~ 620 at high frequency region (18 MHz), both with dielectric constant of ~5, which considered as excellent dielectric properties.
　　Ceramic bulks sintered at 870 ~ 970℃ for 8 hours with 15 ~ 20 wt% Bi2O3 additives have thermal expansion coefficients of 17 ~ 20 x 10-7 /℃, which match the sili　con’s (30 x 10-7 /℃) very well.
　　The resistivity coefficient of the ceramic bulks without Bi2O3 additives were lower compared to those with Bi2O3 additive. As the amount of Bi2O3 additives increased, the resistivity coefficient increased and became stable. The best resistivity coefficient found in this study was 4 x 1011 Ωcm.

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