Studies of Lead-iron-phosphate Glasses by Raman, Mössbauer and Impedance Spectroscopy

The effect of Fe2O3 content on electrical conductivity and glass stability against crystallization in the system PbO-Fe2O3-P2O5 has been investigated using Raman, XRD, Mössbauer and impedance spectroscopy. Glasses of the molar composition (43.3 − x)PbO-(13.7 + x)Fe2O3-43P2O5 (0 less-than-or-equals, slant x less-than-or-equals, slant 30), were prepared by quenching melts in the air. with increasing Fe2O3 content and molar O/P ratio there is corresponding reduction in the length of phosphate units and an increase in the Fe(II) ion concentration, which causes a higher tendency for crystallization. Raman spectra of the glasses show that the interaction between Fe sites, which is essential for electron hopping, strongly depends on the cross-linking of the glass network. The electronic conduction of these glasses depends not only on the Fe(II)/Fetot ratio, but also on easy pathways for electron hopping in a non-disrupted pyrophosphate network. The Raman spectra of crystallized glasses indicate a much lower degree of cross-linking since more non-bridging oxygen atoms are present in the network. Despite the significant increase in the Fe2O3 content and Fe(II) ion concentration, there is a considerable weakening in the interactions between Fe sites in crystalline glasses. The impedance spectra reveal a decrease in conductivity, caused by poorly defined conduction pathways, which are result of the disruption and inhomogeneity of the crystalline phases that are formed during melting