Netsu Sokutei, 34 (5), p. 206, (2004)



High Temperature Microbalance Technique for the Determination of the Metal Oxides Nonstoichiometry under Controlled Atmosphere

酸素不定比性は,金属酸化物の性能に影響を与え,様々な優れた機能性を与える。よって,酸素不定比量の測定は,金属酸化物の基礎物性の理解には大変重要となる。金属酸化物の酸素不定比性は,雰囲気中の酸素との相互作用の結果により生じ,その正確な測定には,一定温度において酸素分圧をパラメータとした雰囲気に対して雰囲気制御高温微重量天秤測定を行う事が多い。 雰囲気制御高温微重量測定は,酸素ポテンシャルに対する重量変化から,その酸素不定比量を測定するものであり,測定原理は単純である。しかし,高温かつ雰囲気制御下での平衡測定では測定が長期に亘ることもある事から,正確な測定には精度と長期間安定性に関して留意すべき点が少なくない。それらを中心に,雰囲気制御高温微重量天秤による平衡測定方法について重要な測定時の注意点などを紹介する。
Various properties of the metal oxides are strongly affected by the nonstoichiometry. Therefore, nonstoichiometry is very important for understanding the basic character of the metal oxides. Nonstoichiometry of the metal oxides is often measured by the gravimetric measurements at high temperature under controlled atmospheres. As the vapor pressure of the metal is negligibly small compared to the oxygen, the nonstoichiometry behavior of the metal oxides is often measured as a function of the oxygen partial pressure. In this article, a brief review is made for the experimental technique of nonstoichiometry measurements by means of high temperature gravimetry under controlled gas-atmospheres:  The oxygen nonstoichiometry is measured as the weight change at different oxygen partial pressures. The principle of the measurement is very simple. However, as the measurement is carried out at the equilibrium conditions at the high temperature under controlled oxygen partial pressures, and moreover, as the measurements often extend over a long period of time, the precision and long-time stability of the measuring system are important. Other important reminders will also be shown for the measurements procedure of the gas controlled high temperature microbalance.