Surface properties of tellurite and fluorotellurite glasses
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D. Briggs and E.F. Smith Wolfson Centre for Materials Research, School of Mechanical, Manufacturing and Materials Engineering, University Park, University of Nottingham, Nottingham, NG7 2RD, United Kingdom; and Centre for Surface Chemical Analysis, School of Chemistry, University Park, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
A.B. Seddon Novel Photonic Glasses Research Group, School of Mechanical, Manufacturing and Materials Engineering, University Park, University of Nottingham, Nottingham, NG7 2RD, United Kingdom (Received 26 March 2006; accepted 6 March 2007)
The surface properties of some freshly cleaved, or polished, quaternary tellurite glasses (TeO2-ZnO-Na2O-Yb2O3 and TeO2-ZnO-Na2O-GeO2) and a proposed ternary fluorotellurite core/clad optical fiber pair (TeO2-N a2O-ZnF2) were investigated by means of x-ray photoelectron spectroscopy and chemical durability. Semiquantitative chemical analysis of the x-ray photoelectron spectroscopy spectra of cleaved tungsten-tellurite and fluorotellurite glasses showed good agreement with the batched at.% values when taking into account the effects of processing (e.g., melt fluorine volatilization), and the samples seemed to exhibit negligible hydrolysis. However, spectra of polished surfaces did not yield useful data because of masking of the glass “signal” from organic contamination at the sample surface. The chemical durability of these glasses were studied; specifically, the glass resistance to the attack and the etchability of various acids (aqueous HF, H2SO4, and HCl), alkali (aqueous NaOH), and water at 15, 21, and 60 °C were obtained by simple mass loss experiments and optical microscopy. Based on the appearance of the glass surfaces after immersion in these solutions, aqueous HF was found to be the most promising etchant, however, infrared spectra showed that significant OH was introduced into the glass. Attack of the fluorotellurite glasses was found to proceed at a higher rate in water at 60 °C compared with room temperature, and at both temperatures was shown to be diffusion controlled, with an Arrhenian activation energy estimated as 57 kJ mol−1.
I. INTRODUCTION
Tellurite glasses have been studied since 1913 when Lenher et al.1 observed sodium di- and tetratellurite fused below red heat to form clear glasses. Interestingly, it was also noted in this work that the sodium-tellurites were readily soluble in water. However, the first major systematic study undertaken on tellurite glasses was by Stanworth in 1952.2,3 Stanworth proposed that the glass forming ability of TeO2 glasses could be explained by the
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Address all correspondence to this author. Present address: Department of Materials, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, United Kingdom. e-mail: [email protected] DOI: 10.1557/JMR.2007.0223 J. Mater. Res., Vol. 22, No. 6, Jun 2007
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Pauling electronegativity of Te+4 (2.1), which is in the range of other good glass forming cati
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