Oxygen Evolution and Uptake Properties of Functional Oxides and The Influence of Hydrogen Dissolved in Them

利用高灵敏度的闭式氧分析仪研究了ITO （In_2O_3+SnO_2）粉末中氧的演化和吸收。测定了P (O_2) =10^<-4>atm时的P (O_2) -C (O) -T曲线；然而，这取决于加热-冷却历史。粉末XRD分析未观察到析出现象，因此可以得出结论，域界面的界面能对氧的热力学演化和吸收有重要作用。我们对ITO样品进行了类似的实验，该样品一直保存在空气中，因此应该包含水分或氢气。得到的P (O_2) -C (O) -T曲线没有变化，ITO中涉及的氢量可以忽略不计。然而，据报道，水蒸气在ITO中的作用是重要的。因此，我们研究了与ITO结构相似的Sc_2O_3-HfO_2化合物和La_2Zr_2O_7中H_2和H_2O的溶解。对于掺杂In_2O_3的La_2Zr_2O_7，观察到H_2O的明显溶解；溶解在ITO中的H_2O仍需进一步研究。我们还测量了ITO的电导率和析氧量。西格玛的变化对应于氧的释放和可能吸收的CO气体的解吸。ITO的表面导电应从析氧角度来考察。

The evolution and uptake of oxygen in ITO (In_2O_3+SnO_2) powders were investigated utilizing a closed-system oxygen analyzer with high sensitivity. P (O_2) -C (O) -T curve for P (O_2) =10^<-4>atm was determined ; however, it depend on heating-cooling history. A precipitation coud not be observed by Powder XRD analysis, and therefore we may conclude that the interfacial energy of domain interface has an important role on the evolution and uptake of oxygen thermodynamicaly. We conducted a similar experiment with ITO sample which had been kept in air and therefore supposed to involve moisture or hydrogen. The P (O_2) -C (O) -T curve obtained was not changed, and the amount of hydrogen involved in ITO could be negligible. Nevertheless, it has been reported that the role of water-vapor in ITO is important. Thus, we examined the dissolution of H_2 and H_2O in Sc_2O_3-HfO_2 compounds and La_2Zr_2O_7, which have similar structures to ITO.For La_2Zr_2O_7 doped with In_2O_3, a distinct dissolution of H_2O was observed ; the H_2O dissolved in ITO is still needed to investigate. We also measured the electrical conductivity sigma of ITO tobether with the measuremetns of oxygen evolution. Change in sigma corresponds to the oxygen evolution and also desorption of probably CO gas absorped. The surface conduction of ITO should be examined in terms of oxygen evolution.