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 (N4) 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.