Transition metal ions in silicate melts. IV. Cobalt in sodium silicate and related glasses

Optical measurements have been made on glasses quenched from a series of sodium silicate melts as well as germanate, borate, and phosphate liquids containing CoO. The spectral data show that Co⁺² is the species stabilized in oxide melts heated in air. The observed bands occur at 2700–3850, 5750–7900, and 15 500–18 600 cm^-1. The independence of the optical parameters from melt composition and known melt structures, the high relative intensity of the highfrequency band, and the low calculated value of the Racah B parameter relative to the free ion value indicate that Co⁺² forms a distinct tetrahedral complex in the quenched melt.