Structural and EPR studies of Cu2+ ions in NaPO3 – Sb2O3 – CuO glasses

Reference Presenter Authors
(Institution)
Abstract
10-052 DOUGLAS FAZA FRANCO FRANCO, D.F.(Estadual University of São Paulo); Carvajal, E.E.(Universidade Federal de São Carlos); Donoso, J.P.(Universidade de São Paulo); Magon, C.J.(Universidade de São Paulo); Fares, H.(Instituto de Química, Universidade Estadual Paulista); Silva, M.P.(Universidade Federal de Juiz de Fora); Sant'Ana, A.(Universidade Federal de Juiz de Fora); Nalin, M.(Instituto de Química, Universidade Estadual Paulista);

Glasses based on sodium polyphosphate (NaPO3)n containing antimony(III) and copper(II) oxide have been studied. The presence of Sb2O3 in the glass composition is due to its characteristic as a reducing agent, since that the antimony has the property of reduce metallic components of the glass. In this work, we report the electron paramagnetic resonance (EPR) analysis of NaPO3-Sb2O3 glasses using as the Cu2+ spin probe. In addition, the thermal, structural and spectroscopies analyses were performed by Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD) analysis, UV-Vis and Photoluminescence (PL) spectroscopies, respectively. In this work, the (100-x)NaPO3 - 80Sb2O3xCuO (P80SxCu) glasses, where (x = 0.25, 0.50, 0.75 and 1.0 mol% of CuO) and (99.5-y)NaPO3-ySb2O3-0.5CuO (PyS0.5Cu) glasses (y = 20, 30 and 80 mol% of Sb2O3) were synthesized by melt-quenching method using platinum crucibles at 1000 °C for 10 minutes. The DSC curves for all samples showed the presence of glass transition phenomenon and XRD patterns presented a halo amorphous, which confirm the vitreous nature of all samples analyzed. The UV-Vis spectra of the glasses showed a transparent window from 450 to 800 nm. The EPR signals intensities were investigated as a function of the copper concentration and Sb2O3 content in the (PyS0.5Cu) and (P80SxCu) glasses. The EPR results showed that the increase of Sb2O3 concentration on the PyS0.5Cu glasses decreased the Cu2+ signals, suggesting that the Sb3+ oxidizes to Sb5+, transferring electrons to Cu2+ species to create the EPR silent Cu+ specie. On the other hand, for the P80SxCu glasses, the Cu2+ intensity increase with the copper concentration in glasses with the same Sb2O3 content. According to EPR parameters and PL spectra (excited at 380 nm) of PyS0.5Cu glasses, the ions Cu2+ ions were preferentially found in a distorted octahedral geometry, while Cu+ is in a tetragonal arrangement, according to Jahn-Teller effect.


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