Specific trends in phosphate glass crystallization
Résumé
This paper focusses on investigating and comparing the congruent crystallization of phosphate glasses with different degrees of polymerization. The study was performed both on powders, with different size fractions, and coarse particles which can be assimilated to bulk. From DSC experiments, corroborated by SEM analysis, it was demonstrated that LiPO3 crystallizes from surface whereas LiGe2(PO4)3 crystallizes in the whole volume. Sn2P2O7 presented both phenomena, the nucleation time lag being short enough to observe internal crystallization at the laboratory time scale. Using the non-isothermal Ozawa method, the kinetic parameters of the overall devitrification process were determined in terms of the Avrami exponent and of the activation energy for crystallization. The temperature of the maximum nucleation rate was calculated by using the nucleation adiabatic theory. For the achievement of this calculation, the heat capacity temperature dependence up to melting was determined from DSC experiments. The results were found in a good agreement with the SEM observation and the results of the non-isothermal crystallization study. © 2020 Elsevier B.V.
Mots clés
Activation energy
Germanium compounds
Glass
Isotherms
Lithium compounds
Nucleation
Particle size analysis
Specific heat
Temperature distribution
Tin compounds
Adiabatic theory
Coarse particles
Degrees of polymerizations
Devitrification process
Internal crystallization
Nonisothermal crystallization
Nucleation rate
Temperature dependence
Crystallization
Domaines
Chimie
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