Absorption Spectra and Concentration‐Dependent Luminescence of Mn 2+ in Silicate Glasses

Glasses activated with Mn 2+ exhibit green to red luminescence. A widely accepted model proposes that these colors denote 4‐ and 6‐coordination, respectively, for Mn 2+ . The luminescence and absorption of Mn 2+ ‐activated silicate glasses were studied; the luminescence changed from green to red with increasing Mn 2+ concentration. The difference in the intensities of emission bands with peaks near 520 and 620 nm accounts for the luminescent color. No experimental evidence for a change in coordination from 4 to 6 was found. Exchange‐coupled groupings are proposed to explain red emission in these glasses and possibly in borate and phosphate glasses studied by other workers. Improved resolution of bands and theoretical calculations demonstrate that a covalent‐octahedral Mn 2+ species can account for the spectral data for the silicate glasses.