Studies have been made on the formation of oxide solid solutions, and on their structural and electronic properties. Three different oxide systems have been investigated: CoO-MgO, MnO-CaO and CuIn2O4-CdIn2O4 CoO-MgO (0-10 mo1 % Co) has been prepared in low, medium and high surface area (LSA, MSA and HSA) forms. The lattice parameter, ao, was determined by X-ray diffraction (XRD) for LSA and MSA specimens, and by electron diffraction for HSA specimens where severe line broadening precludes accurate determination of ao by XRD. The increase in ao with [Co] was found to be identical in all cases, which implies that solid solution is maintained even at very small particle size (D <500 A). However, reflectance spectra of MSA (D = 500 - 1.000 A) and HSA (D = 200 - 500 A) oxides show that some Co in the surface layers of finely-divided outgassed CoO-MgO is not in octahedral coordination. MnO-CaO, prepared by heating coprecipitated carbonates at 1273 K in vacuo, has been shown to form a solid solution over the whole composition range in spite of the large difference (22%) in cation radius. ESR studies showed the site symmetry of Mn2+ to be accurately cubic. The onset of magnetic interactions between manganese ions takes place when [Mn] = 1% for the dipole interaction and when [Mn] = 3% for the exchange interaction. By co-addition of Na+ ions small amounts of Mn3+ can be incorporated in solid solution in CaO. CuIn2O4 specimens have been prepared by solid state reaction between CuO, CdO and In2O3 at three different temperatures (1173, 1223 and 1323 K) and, by X-ray analysis, solubility limits have been found at 2.4, 2.9 and 5.2 mol % Cu respectively. A study has also been made on the crystal structure of CdIn2O4.
|Date of Award||1976|