Preparation method and thermal properties of samarium and europium-doped alumino-phosphate glasses.

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Abstract

tThe present work investigates alumino-phosphate glasses from Li2O-BaO-Al2O3-La2O3-P2O5systemcontaining Sm3+and Eu3+ions, prepared by two different ways: a wet raw materials mixing route fol-lowed by evaporation and melt-quenching, and by remelting of shards. The linear thermal expansioncoefficient measured by dilatometry is identical for both rare-earth-doped phosphate glasses. Compar-atively to undoped phosphate glass the linear thermal expansion coefficient increases with 2 × 10-7K-1when dopants are added. The characteristic temperatures very slowly decrease but can be consideredconstant with atomic weight, atomic number and f electrons number of the doping ions in the case of Tg(vitreous transition temperature) and Tsr(high annealing temperature) but slowly increase in the case ofTir(low annealing temperature-strain point) and very slowly increase, being practically constant in thecase of TD(dilatometric softening temperature). Comparatively to undoped phosphate glass the charac-teristic temperatures of Sm and Eu-doped glasses present lower values. The higher values of electricalconductance for both doped glasses, comparatively to usual soda-lime-silicate glass, indicate a slightlyreduced stability against water. The viscosity measurements, showed a quasi-linear variation with tem-perature the mean square deviation (R2) being ranged between 0.872% and 0.996%. The viscosity of dopedglasses comparatively to the undoped one is lower at the same temperature. Thermogravimetric analy-sis did not show notable mass change for any of doped samples. DSC curves for both rare-earth-dopedphosphate glasses, as bulk and powdered samples, showed Tgvalues in the range 435-450◦C. Bulk sam-ples exhibited a very weak exothermic peak at about 685◦C, while powdered samples showed two weakexothermic peaks at about 555◦C and 685◦C due to devitrification of the glasses. Using designed meltingand annealing programs, the doped glasses were improved regarding bubbles and cords content andstrain elimination.
Original languageUnknown
Pages (from-to)1429-1435
JournalMaterials Science and Engineering B
Volume178
Issue numberNA
DOIs
Publication statusPublished - 1 Jan 2013

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