Thermo-kinetic and structural characterization of Ce-doped glasses based on Bioglass 45S5

Abstract

Thermo-kinetic behavior of Ce-doped 45S5 bioactive glass (addition of CeO2 up to 1.5 mol.%) was explored by means of calorimetry and thermomechanical analysis. The apparent activation energy of structural relaxation was estimated to vary in the 540-670 kJ mol-1 range. The relaxation process exhibited broad distribution of relaxation times and the relaxation motions were found to only weakly depend on the material's structure. The activation energy of viscous flow was found to vary in the 585-615 kJ mol-1 range; the viscosity itself showed Arrhenian behavior within 107-1011 Pa s. Thermal stability of the glasses was found to be non-monotonous and generally very low, with the most stable glass composition being 45S5 + 0.5 mol.% CeO2. The cold crystallization was found to behave autocatalytically, with the activation energy decreasing from 360 to 310 kJ mol- 1 with the gradual addition of CeO2. While the bulk glasses were crystallization-resistant up to 620 degrees C, the powdered material with CeO2 content >= 1 mol.% was predicted to crystallize even at temperatures slightly above the glass transition temperature.