Thermal and crystallization kinetics of yttrium-doped phosphate-based glasses

Yttrium-doped glasses have been utilized for biomedical applications such as radiotherapy, especially for liver cancer treatment. In this paper, the crystallization behavior of phosphate-based glasses doped with yttrium (in the system 45P(2)O(5)-(30 - x) Na2O-25CaO-xY(2)O(3)-where x = 0, 1, 3 and 5) have been investigated via Differential Scanning Calorimetry (DSC) using nonisothermal technique at different heating rates (5 degrees C, 10 degrees C, 15 degrees C and 20 degrees C/min). The glass compositions were characterized via EDX, XRD, Density and Molar volume analysis. The Moynihan and Kissinger methods were used for the determination of glass transition activation energy (E-g) which decreased from 192 to 118 kJ/mol (Moynihan) and 183 to 113 kJ/mol (Kissinger) with increasing yttrium oxide content. Incorporation of 0 to 5 mol% Y2O3 revealed an approximate decrease of 71 kJ/mol (Ozawa and Augis) for onset crystallization (E-x) and 26 kJ/mol (Kissinger) for crystallization peak activation energies (E-c). Avrami index (n) value analyzed via Matusita-Sakka equation suggested a one-dimensional crystal growth for the glasses investigated. SEM analysis explored the crystalline morphologies and revealed one-dimensional needle-like crystals. Overall, it was found that these glass formulations remained amorphous with up to 5 mol% Y2O3 addition with further increases in Y2O3 content resulting in significant crystallization.