Influence of iron ions on the structural and magnetic properties of some zinc-phosphate glasses

Glasses in the (Fe2O3)x·(P2O5)40·(ZnO)60−x (0 ≤ x ≤ 30 mol%) system have been prepared by the melt-quenching technique. The structural and magnetic properties of these glasses were investigated by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. The XRD pattern for the prepared samples shows their vitreous state only for x ≤ 20 mol%. For the samples containing 30 mol% Fe2O3 the presence of a unique crystalline phase, FePO4, embedded in an amorphous matrix was evidenced. FTIR spectroscopy data suggest that the iron ions play the network modifier role in the studied glasses. The addition of iron oxide leads to the breakage of PO bonds and the formation of the P–O–Fe bonds. The presence of the Fe–O–P bonds for the samples with higher iron oxide content in the studied system improves their chemical durability. The increases of iron ions content of the samples determine a gradual decrease in the number of bridging oxygen ions respectively the increase of the number of non-bridging oxygen ions. EPR and magnetic susceptibility measurements show the presence of the Fe3+ ions in sites of distorted octahedral symmetry and as well as in clustered formations containing both Fe3+ and Fe2+ ionic species. Dipolar and superexchange interactions involving iron ions were revealed depending on the iron content of the sample.