SOME BONDING ASPECTS OF COBALT IONS IN PHOSPHATE GLASSES

Phosphate glasses containing different concentrations of CoO, Na2O and CaO were prepared. Their visible, near IR spectra and paramagnetic moments were measured. The results indicated that in all the glasses studied, cobalt existed in the +2 formal oxidation state. The microsymmetry of the cobalt complex species (Co2+ surrounded by oxygens) was found to change from octahedral, Oh, at low metal oxide concentrations to tetrahedral, Td, at high oxide concentrations. There is evidence that the change takes place via the formation of an 8-coordinated species that has common symmetry elements with each of the Oh and Td symmetries. The covalent character of the CoO bond was found to increase with the increase in the metal oxide concentration indicating an increase in the CoO orbital overlap. © 1979.