柠檬酸凝胶法制备Mn-Ni-Fe基负温度系数热敏陶瓷

采用柠檬酸凝胶法制备锰-镍-铁基前驱体,在300℃煅烧干燥的前驱体得到纳米粒度粉末,压制成圆片坯体后在1100～1300℃烧结得到负温度系数(negative temperature coefficient,NTC)热敏陶瓷样品。研究了粉体和烧结样品的相结构、微观形貌、电性能和热敏特性。结果表明:合成粉体的纳米颗粒为单相Mn1/3Ni2/3Fe2O4尖晶石,粉体具有高化学均匀性。烧结的Mn1/3Ni2/3Fe2O4陶瓷样品具有均匀的微观结构,陶瓷样品的烧结密度和材料敏感指数β随着烧结温度的增加而增加。测量温度为50～150℃范围时,1300℃烧结的Mn1/3Ni2/3Fe2O4样品,其β可高达4300K。

PREPARATION OF Mn-Ni-Fe BASED NEGATIVE TEMPERATURE COEFFICIENT THERMISTORS VIA A CITRATE GEL ROUTE

Mn-Ni-Fe based precursor was prepared via a citrate gel route. The nano-crystalline powder was obtained by calcining dried precursor at 300 ℃ ,and then a negative temperature coefficient （NTC） thermistor ceramic was prepared after sintering the compacted disc samples at 1 100-1 300 ℃. The phase composition,morphology,electronic property and thermo-sensitivity of the ceramic were investigated. The results show that the nano-crystalline particles of the powder are single-phase Mn1/3Ni2/3Fe2O4 spinel,and it possesses highly chemical homogeneity. The sintered Mn1/3Ni2/3Fe2O4 ceramics have homogeneous microstructure,and the sintered density and NTC sensitivity index β of the ceramic samples increase with the increase of sintering temperature. The sensitivity index β of the Mn1/3Ni2/3Fe2O4 ceramic sample sintered at 1 300 ℃ can be as high as 4 300 K （measured in the temperature range of 50-150 ℃ ）.