Optical and EPR Studies of Redox Interactions of Polyvalent Ions (Cr, Cu) in Glass

Chromium centers in isolated Cr ions and Cr(III)-Cu(II) redox interactions were investigated by optical and EPR spectra. Line shapes and intensities of high-field Cr(III)-Cu(II) superimposed EPR absorption lines were sensitive to alkali content of host glasses. High-field chromium g values (1.94 to 1.99) and intensities (190 to 3600) were calculated. The increase in g values from 1.96 to 1.98 is related to an increase in Cr(V) and to a conversion from Cu(I) to Cu(II) with increased alkali content. Two components of Cr powder spectra near g = 2.0 and g = 5.0 correspond to isolated octahedral Cr centers described by Landry et al. Cr-Cr pair structure was not observed for low Cr₂O₃ concentrations. Three components of optical absorption bands near 340 nm, 430 to 460 nm, and 600 nm were measured in Cr(III)-Cu(II) redox systems. Electronic interactions of Cr(III)-Cu(II) redox systems and the structure of Cr centers are discussed.