Phase transformation and microstructural evolution after heat treatment of a terbium-doped lithium–aluminum phosphate glass |
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Authors: | Roque S Soares Regina C C Monteiro Maria M R A Lima Bogdan A Sava Mihail Elisa |
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Affiliation: | 1. Department of Materials Science, CENIMAT/I3N, Faculty of Sciences and Technology, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal 2. Department of Optospintronics, National Institute of R & D for Optoelectronics, INOE 2000, 77125, Magurele, Romania
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Abstract: | The crystallization kinetics and phase transformation of a transparent Tb3+-doped lithium–aluminum phosphate glass, prepared by melt quenching, were investigated. The energy associated to the glass transition and the crystallization parameters (activation energy for crystallization and Avrami exponent) were evaluated by different methods using the experimental data obtained by differential thermal analysis performed at different heating rates. Using an isoconversional method to determine the change of the activation energy for crystallization with the fraction of crystallization, it was verified that with the increase in the fraction of crystallization from 0.1 to 0.9, the value of the activation energy decreased slightly from ~370 to ~310 kJ mol?1 and that the Avrami exponent varied from 0.8 to 1, suggesting a surface crystal growth mechanism. Observation of the microstructural evolution of heat-treated glass samples confirmed a surface crystallization process revealing spherulitic crystals constituted mainly by aluminum metaphosphate. |
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