Structural properties of unconventional lead cuprate glass
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Glass formation and structural properties of the unconventional lead cuprate glasses of compositions (CuO)x (PbO)ioo-x (mol%), are reported for the first time. X-ray diffraction and electron microscopic studies show that the glass formation occurs for x = 15-50 mol%. The compositional dependence of the density, molar volume, and glass transition temperature suggests that all glass compositions in this domain have the same topology and network connectivity. The glass structure is built up of [PbO4] tetrahedral units. On heat treatment above glass transition temperatures, the glasses crystallize to CuO and PbO. Electron Spin Resonance (ESR) spectra of the glass compositions consist of broad resonance lines.
I. INTRODUCTION Oxide glasses based on PbO are of great interest because they can form amorphous materials without traditional network formers like SiO2, and they can be used to produce glass ceramics, layers for optical and optoelectronic devices, thermal and mechanical sensors, and reflecting windows.1^* However, few studies have been reported on the PbO-based glasses.5-6 Lead and bismuth oxides can be incorporated in high concentration in the glasses based on traditional network formers. 78 It was pointed out7 that Pb +2 cations are highly polarizable and the asymmetry of their polyhedra inhibits crystallization processes in the melts in which they participate. In silicate glasses when lead oxide is added, PbO acts as a network modifier for low concentration, while at high concentration, it is capable of participating in the network.8 Nuclear magnetic resonance studies9 confirm the 4-coordination of lead in high ( > 5 0 m o l % ) P b O glasses. Recently, glasses in which PbO is the main network former have been synthesized and their structures have been studied. '•I0~12 The purpose of the present paper is to study the glass formation domain and structure of the binary CuO-PbO glasses, using PbO as the basis of the glass network former instead of conventional glass-forming oxides.
prepared and heat-treated at different temperatures for different durations of time were recorded in a x-ray diffractometer (Philips, model PW 1840). The scanning electron micrographs of the polished surfaces of the samples were taken in a scanning electron microscope (Hitachi, model S-415A). A ~ 150 A thick gold coating was deposited on the polished surfaces of the samples by vacuum evaporation for conducting layers. The atomic absorption was carried out in an atomic absorption spectrometer (Varian, model AA 1475) to determine the final glass compositions, as well as to estimate the total copper ion concentrations. The density of the samples was
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II. EXPERIMENTAL PROCEDURE
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Samples of compositions (CuO)x (PbO)10o_x, where x = 15-50 mol%, were prepared using reagent grade chemicals PbO (Koch Light, UK) and CuO (Loba, India). The mixtures of these chemicals were melted in alumina crucibles in the temperature range 1100-1250 °C
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