Characterization and Surface Reactivity of Finely-Divided CoO-MgO Solid Solutions
CoO-MgO (0–10 mol % Co) has been prepared in low, medium and high surface area (LSA, MSA and HSA) forms. ao for HSA oxides (mean particle size has been determined in vacuo by electron diffraction. The increase of ao with [Co] is identical to that of sintered LSA oxides prepared at 1300°C. Magnetic data confirm that Co(II) ions are well dispersed in true solid solution in both MSA and HSA oxides.
Reflectance spectra of MSA \( (\bar D = 50 - 100nm) \) and HSA \( (\bar D = 20 - 50nm) \) oxides show that some Co in the surface layers of finely-divided outgassed CoO-MgO is in tetrahedral coordination. Exposure to the atmosphere or oxygen destroys the surface spectrum, though in oxygen the destruction is not complete.
HSA MgO \( (\bar D = 14nm) \) has an anomalously low ao attributed to the surface energy effect predicted by previous authors.
KeywordsHigh Surface Area Weiss Constant Schottky Defect Surface Spectrum Surface Energy Effect
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