Absorption Spectroscopy Analysis of Calcium–Phosphate Glasses Highly Doped with Monovalent Copper

José A. Jiménez, University of North Florida

Abstract

CaO–P2O5 glasses with high concentrations of monovalent copper ions were prepared by a simple melt–quench method through CuO and SnO co-doping. Spectroscopic characterization was carried out by optical absorption with the aim of analyzing the effects of Cu+ ions on the optical band-gap energies, which were estimated on the basis of indirect–allowed transitions. The copper(I) content is estimated in the CuO/SnO-containing glasses after the assessment of the concentration dependence of Cu2+ absorption in the visible region for CuO singly doped glasses. An exponential dependence of the change in optical band gaps (relative to the host) with Cu+ concentration is inferred up to about 10 mol %. However, the entire range is divided into two distinct linear regions that are characterized by different rates of change with respect to concentration: 1) below 5 mol %, where the linear dependence presents a relatively high magnitude of the slope; and 2) from 5–10 mol %, where a lower magnitude of the slope is manifested. With increasing concentration, the mean Cu+−Cu+ interionic distance decreases, thereby decreasing the sensitivity of monovalent copper for light absorption. The decrease in optical band-gap energies is ultimately shown to follow a linear dependence with the interionic distance, suggesting the potential of the approach to gauge the concentration of monovalent copper straightforwardly in amorphous hosts.