FTIR and XPS studies of low-melting PbO-ZnO-P2O5 glasses

Shea range structure and oxygen bending of a series of low-melting, water-resistant lead-zinc metaphosphate and polyphosphate glasses were characterized by Fourier transformed infrared (FTIR) spectrophotometer and X-ray photoelectron spectroscopy (XPS). FTIR studies showed that these glasses consist of long chains of phosphate tetrahedra. Decreasing P2O5 content and increasing PbO and/or ZnO contents lead to the formation of P-O-Pb(Zn) linkages through the delocalization of P=O and P-O- bonds. The length of phosphate chains decreases with increasing PbO and/or ZnO contents. Binding energies of P2p, Pb4f(7/2), Pb4f(5/2), Zn2p(3/2) and O-1s have been determined from the respective XPS spectra. The O-1s spectrum was deconvoluted based on three peaks, symmetric bridging oxygen (P-O-P), nonbridging oxygen (P-O-, including P=O) and asymmetric bridging oxygen (P-O-Pb and/or P-O-Zn). The fraction of P-O-Pb(Zn) bondings is quantitatively worked out. It is compositionally dependent and is maximized at a ZnO content of 10 mol%. More covalent P-O-Pb(Zn) bondings are created for glasses with higher PbO contents in polyphosphate glasses to a structure with enhanced connectivity and cross-linking which explains the increase in T-g and T-d, and the decrease in thermal expansion coefficient and dissolution rate.