以化學共沉法製備Cu-Co-Ni-Mn系NTC陶瓷之研究

Preparation of Cu-Co-Ni-Mn system NTC Ceramics by the Chemical Coprecipitation

劉建志(Chien-Chih Liu)

指導教授 ： 林和龍 ； 胡毅

大同大學/工程學院/材料工程學系所/碩士(2005年)

摘要

根據電學公式可得知，當材料電阻愈低時，其產生出的焦耳熱也就愈小，所以降低NTC的電阻在電路設計的匹配上，將有更多選擇的空間，但NTC的電阻穏定性亦是相當重要的考慮因素；一般阻值愈低，穏定性愈差。因此為了改善低阻值NTC穏定性，化學共沉法是一可採用的粉末製備方法。化學合成法的原料是在溶液狀態下混合，粉體的均勻性高、平均粒徑小、化學活性較大，所以反應較傳統之固態反應法快且完全。故本研究是以化學共沉法製備Cu-Ni-Mn系、Co-Ni-Mn系和Cu-Co-Ni-Mn系NTC陶瓷；燒結條件各為1000、1100及1200℃。本研究採用的共沉法是以硝酸鹽和草酸銨皆製備成0.2M之水溶液，並將之加熱混合，形成草酸鹽沉澱物。由實驗的結果得知以化學共沉法所製備之NTC：(1)成分的正確性在97~99%之間。(2)形成尖晶石相的溫度較固體反應法低300℃左右。(3)NTC材料的緻密性隨增加Cu或Co的量而變大，緻密性愈好使得電阻率愈低。(4)Ni-Mn-O系統NTC之電阻率，隨著增加Cu或Co的量而減少。(5)Ni-Mn-O系統NTC之室溫電阻率，添加Cu較加Co要低很多，從774~844降低至13~27 (Ω-cm)。(6)電阻率及電阻穩定性較固態反應法合成佳。(7)Ni-Mn-O系統NTC之晶格常數隨著增加Cu或Co的量而減少；晶格常數的降低，有助於降低電阻率。(8)當NTC的室溫電阻率低於200(Ω-cm)時，其測量儀器的導線電阻值必需校正。(9)化學共沉法製作之NTC，含Cu量愈高有助於NTC電阻穩
定性的提昇。

關鍵字

尖晶石 ； 化學共沉法 ； 負溫度係數 ； 熱敏電阻

並列摘要

According to the electricity formula, when the material is the lower in resistance, its produced joule-heat is small too. So reduce the resistance of NTC in the match that the design of circuit , there is space chosen more, but the resistance of NTC stability it is also a quite important factor for consideration. In order to improve stability of low resistance NTC , coprecipitation is that suitable method to prepare powders. The raw materials of the coprecipitation are mixing under the solution state, powder of homogeneous is high , low mean grain size , high chemical activation , so reflects the reaction faster and complete than the traditional solid state . Therefore prepare of Cu-Ni-Mn , Co-Ni-Mn , Cu-Co-Ni-Mn system NTC ceramics by the chemical coprecipitation for study. The sintering condition is each 1000 , 1100 and 1200 ℃. Coprecipitation is to all prepare into the aqueous solution of 0.2M of nitrate and oxalic acid ammonium , and mix its heating form the salt precipitate of oxalic acid. According to the result of coprecipitation, there are several advantages. The precision of composition could reach 97%~99%. The formation of spinel structure was 300oC lower than that proceeding with solid-state reaction. The densification has enhanced as the content of cobalt or copper increased and the resistivity was also decreased. The resistivity of NTC with copper (774~844Ω-cm) was much lower than that with cobalt (13~27Ω-cm) measuring at room temperature. The resistivity and thermal stability has better performance than that proceeding with solid-state reaction. The lattice constant has decreased as the content of copper or cobalt dropped. The most important thing is that the wire should be calibrate since the resistivity of NTC at room temperature is less that 200Ω-cm. The higher content of copper could highly enhance the stability of NTC.

並列關鍵字

coprecipitation ； NTC ； spinel ； thermistor

參考文獻

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