Browsing by Author "Yang, B"

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    Comparisons of tin depth profile analysis in float glass
    Townsend, PD; Can, N; Chandler, PJ; Farmery, BW; Lopez-Heredero, R; Peto, A; Salvin, L; Underdown, D; Yang, B
    Data are presented showing the profile of tin diffusion during the production of float glass, by measuring non-destructively the refractive index profiles in the diffused layer. The optical waveguide modes give unequivocal evidence for an anomaly in the tin depth distribution. The results are compared with those from sectioning techniques, used in depth profiles determined by ion beam analyses and cathodoluminescence (CL). There is agreement between these methods which confirm the presence of a maximum in the tin concentration below the surface which had been in contact with the tin bath (this had been linked by Mossbauer data to a rise in the Sn4+ concentration). The ion beam analyses record different depth profiles for Si, Na and Ca. The Sn4+ feature increases the refractive index, as does the diffusion of Sn2+. The index becomes constant at large tin concentrations. We suggest that Sn4+ is linked to CL emission at 2.68 eV and Sn2+ to the 1.97 eV CL emission. Iron impurities give a 1.73 eV signal. Contrary to earlier suggestions, we prc,pose that the luminescence associated with the presence of tin arises from intrinsic defects stabilised by the tin, not from tin acting directly as a luminescence site. (C) 1998 Elsevier Science B.V.
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    Luminescence of levitated Zr-Ba-La-Al-Na fluoride glass
    Yang, B; Townsend, PD; Can, N; Janke, A; Baniel, P; Blanc, O; Granier, J
    Radioluminescence, cathodoluminescence, and thermoluminescence of Zr-Ba-La-Al-Na (ZBLAN) fluoride glass reveal different aspects of the intrinsic imperfections and impurities which control the emission. Except for weak low-temperature thermoluminescence signals which could be attributed to rare-earth impurities, the majority of the emission bands were common to all samples. These are considered to arise from intrinsic electron-hole recombination processes, either during relaxed exciton emission or at intrinsic defect sites in the glass network. Deconvolution of the spectra indicates that six emission bands occur in all the samples. Production of crystallite inclusions or intrinsic defects enhance the signal intensities. The luminescence is shown to be a useful probe of the quality of the ZBLAN glass, both in the preform stage, and after fiber drawing, even when working with the very high grade material produced by gas film levitation growth.
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    Indications of bulk property changes from surface ion implantation
    Wang, Y; Yang, B; Can, N; Townsend, PD
    In the majority of cases, the effects of ion implantation are confined close to the implant zone but, potentially, the resultant distortions and chemical modifications could catalyse relaxations extending into the bulk substrate. Such possibilities are rarely considered but the present data suggest that high dose ion implantation of ZnO has induced bulk changes. Surface implants with Cu and Tb strongly modified the low temperature bulk thermoluminescence properties generated by X-ray irradiation. Suggestions are proposed for the possible mechanisms for bulk relaxations and structural characteristics, which may indicate where such instability may occur in other lattice structures.