Mn-Co-Ni系酸化物の焼成後の冷却過程における結晶相とサーミスター定数

概要

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Changes in crystal phase and thermistor constant of Mn-Co-Ni oxide, a thermistor material, in cooling process below 1000℃ after firing at 1400℃ were studied. The starting oxide was made of nitrates of Mn, Co arid Ni with a molar ratio of 3.0 : 1.9 : 1.1 by firing at 1400℃. Samples were prepared by annealing the above oxide at various temperatures between 250° and 1000℃ for 24 hours followed by quenching into water. Precise X-ray diffraction analysis of quenched samples revealed the good correlation between the thermistor constant E and the fractional ratio of crystal phases, such as cubic spinel, tetragonal spinel of low-temperature form and tetragonal spinel of high-temperature form, in the sample. It seemed that, in the temperature range between 560° and 650℃, there existed very complicated crystal structures in which the fractional ratio of cubic spinel and tetragonal spinel of high-temperature form varied intricately. Therefore, it is assumed that the change in thermistor constant observed at around 550° to 650℃ in the previous paper can be attributed to the very complicated changes of fractional ratio of cubic spinel and tetragonal spinel of high-temperature form in annealed samples.
社団法人日本セラミックス協会の論文
1990-06-01