| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 94 === Abstract
In this study , we observed the valence of Mo and Fe when different ratio of Mo added to to perform .In the ESCA analysis for samples sintering in reducing atmosphere , we found that the valence of Mo changed from 5 to 6 when the ratio of Mo exceeded more than x=0.6. When the same test for samples sinter in air, the result was different and all the valences of Mo were 6. Because the ionic radius of Mo with valences in 6 was smaller than 5 , it could prove that the oxygen vacancy obtained from sintering in reducing atmosphere can enhance the Mo ion to diffuse into with the Mo valences in 5 when samples contained low ratio of Mo. This phenomenon occurred until the ratio of Mo reached too high , and the Mo started to diffuse into with valences in 6.
In the thermal analysis , we could find the existing of oxygen vacancy in the samples with high ratio of Mo. But its quantity was much less than the sample with low ratio of Mo. In electrical measurement, we also found that the conduction mechanism of electrons and the hopping theory fitted well with the prediction of the quantity of Mo in previous literature when the ratio of Mo was not more than x=1.0 and the temperature was lower than Tc.
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