Physical Properties of Lead Iron Phosphate Glasses Containing Cr₂O₃

The influence of Cr2O3 on glass forming characteristics and physical properties of PbO-Fe2O3-P2O5 glasses has been investigated by Raman and Mössbauer spectroscopies, X-ray diffraction analysis (XRD), Differential Thermal Analysis (DTA), Scanning Electron Microscopy (SEM) and impedance spectroscopy. Glasses of the general composition xCr2O3-(28.3-x)PbO-28.7Fe2O3-43.0P2O5, 0 ≤ × ≤ 10, (mol%) were prepared by conventional melt-quenching technique. The compositions containing up to 4 mol% Cr2O3 formed fully amorphous samples and their Raman spectra show systematic increase in the fraction of orthophosphate Q0 units with increasing Cr2O3 content and O/P ratio. on the other hand, compositions containing 8 and 10 mol% Cr2O3 partially crystallized during cooling and annealing to Fe7(PO4)6, Fe2Pb3(PO4)4 and Cr2Pb3(PO4)4. A high tendency for crystallization of these melts is related to the high O/P (> 4) and Fe2+/Fetot (≈ 0.60) ratios. Electrical conductivity of xCr2O3-(28.3-x)PbO-28.7Fe2O3-43.0P2O5, 0 ≤ × ≤ 10, (mol%) compositions is independent of Cr2O3 and controlled entirely by the polaron transfer between Fe2+ and Fe3+ ions.