- 學位論文
添加物對NiMn2O4熱敏電阻特性之影響
Effects of additives on the electrical properties of NiMn2O4 NTC thermistors
摘要
具有尖晶石結構的(Mn,Ni)3O4氧化物陶瓷體，其溫度係數非常大，電阻會隨著溫度的上升而急速下降，此特性被運用於負溫度係數熱敏電阻元件。化學合成法的原料是在溶液狀態下混合，粉體均勻性高、平均粒徑小、化學活性大，所以反應較傳統之固態反應法快且安全。本研究是以由化學共沉法製備的Mn-Ni系NTC陶瓷為主體，混合不同濃度比例之SiO2及SnO2，在不同的燒結溫度影響之下，探討其對NTC熱敏電阻之各種物理特性的影響。由實驗的結果可以得知以化學共沉法製備出的NiMn2O4粉末：(1)化學共沉法所製備之粉末在煆燒過程中重量損失約為55％。(2)尖晶石相的生成溫度為800℃較傳統固態反應法所得的相圖低約100℃左右，較低之煆燒溫度，可防止粉末粗化。(3)燒結體之孔隙度隨著SiO2添加量的增加而增加，並且在SiO2添加量為10mole%時對其電性有明顯的影響。(4)添加SnO2有助於NiMn2O4之燒結密度，並使試片有較低之電阻率。(5)添加之SiO2以及SnO2會附於晶界上而影響其導電性。
關鍵字
熱敏電阻並列摘要
The (Mn,Ni)3O4 spinel ceramics were investigated as NTC elements. The temperature depending properties, such as resistance and the coefficient of temperature were examined. The powders obtained from the coprecipitation are mixed in solution. This method gives high homogeneous in compositions, low mean grain size, and high chemical activation, so reflects the reaction faster and more complete than the traditional solid state route. From the experimental results of coprecipitation process, there are several advantages. (1)The weight loss of the powder in calcinations process by the chemical coprecipitation is approximately 55％. (2)The temperature of calcinations is 800℃, it is lower 100℃ than the temperature of the traditional solid state route. (3)The sintering densification decrease to the content of SiO2 increase. When the addition of SiO2 is 10mole％, the effect on the electrical properties of NiMn2O4 NTC thermistor is clear. (4) The sintering densification increase to the content of SnO2 increase, and it makes lower resistivity. (5) SiO2 and SnO2 effect the electrical properties on the grain boundary.