Compared to iron phosphate crystals, the structural complexity of iron phosphate glasses is increased by the distortion of Fe-polyhedra and by disproportionation reactions of phosphate anions in the melts [10] and [11]. The fraction of Fe2 + ions in glasses varies with preparation conditions and glass composition. The relative fraction of Fe2 +/Fetot is typically about 20% for glasses obtained by conventional melting (in air) and quenching techniques, although that fraction increases with increasing melt temperature [2], [15] and [16]. For iron phosphate glasses in the O/P range from 3.0 (metaphosphate) to 4.0 (orthophosphate), ferric ions are found in tetrahedral and octahedral sites, and ferrous ions are found in octahedral and perhaps pentahedral sites [11]. Chain-like phosphate anions are linked through these iron sites in a distorted iron chelate structure. The average bond lengths and angles associated with various metal polyhedra also vary with glass composition [17], [18], [19] and [20].