Characterization and spectroscopic studies of multi-component calcium zinc bismuth phosphate glass ceramics doped with iron ions.

Glass ceramics with the composition 10CaF2−20ZnO–(15-x)Bi2O3−55P2O5:x Fe2O3(0≤x≤2.5) were synthesized by melt-quenching technique and heat treatment. These glass ceramics were characterized by XRD and SEM. Spectroscopic studies such as optical absorption, EPR were also carried out on these glass ceramics. From the absorption spectra the observed bands around 438 and 660nm are the octahedral transitions of Fe3+ (d5) ions and another band at about 536 nm is the tetrahedral transition of Fe3+ (d5) ions. The absorption spectrum also consist of a band around 991 nm and is attributed to the octahedral transition of Fe2+ ions. The EPR spectra of the prepared glass ceramics have exhibited two resonance signals one at g1=4.32 and another signal at g2=2.008. The observed decrease in band gap energy up to 2 mol% Fe2O3 doped glass ceramics is an evidence for the change of environment around iron ions and ligands from more covalent to less covalent (ionic) and induces higher concentration of NBOs which causes the depolymerization of the glass ceramic network. [ABSTRACT FROM AUTHOR]