Glass formation in the MoO3–CuO–PbO system

Abstract

Abstract Glasses in the MoO 3 –CuO–PbO system are obtained at high cooling rates (10 4 –10 5 K/s) and characterized using X-ray diffraction (XRD), differential thermal analysis (DTA), infrared (IR) and X-ray photoelectron spectroscopy (XPS). Two glass formation regions are determined: one with compositions having a high MoO 3 content (50–80 mol%) and the other in the PbO-rich compositions (65–80 mol%). In the region of MoO 3 -rich compositions the building units of the amorphous network are МоО 6 , МоО 4 and CuO 4 groups. For these high MoO 3 contents and respectively low PbO concentrations, the lead oxide is supposed to act as a network modifier while at high content PbO is found to be the main glass network former. In latter case the structure of glasses is formed by chains of PbO n ( n = 3, 4) polyhedra, between which there are isolated MoO 4 and CuO 4 complexes. IR and XPS data reveal the existence of Mo–O–Mo, Mo–O–Me(Me’) (where Me = Cu 2+ , Cu 1+ and Me’ = Pb) and Me(Me’)–O–Me(Me’) bonds in the amorphous network. Surprising result is found for low PbO content (10 mol%) where the lead oxide acts as glass network modifier: the actual MoO 3 content drops strongly which is accompanied with a significant increase of the actual CuO content with respect to their nominal MoO 3 –CuO composition. Such effect is not observed in PbO-rich composition (70 mol%) where PbO has a role of network former.