Crystallization kinetics and optical properties of titanium-lithium tetraborate glass containing europium oxide

The crystallization kinetics and optical properties of [60 Li₂B₄O₇-30 TiO₂-10 Eu₂O₃] (mol%) glass sample have been investigated. The present glass sample exhibits three crystallization exothermic peaks (T_p1, T_p2, and T_p3) corresponding to the formation of LiBO₂, Li₂B₄O_7, and EuTiO₃ phases, respectively. The presence of phase separation in the glass sample has been confirmed by scanning electron microscopic (SEM). The mean values of Avrami exponent (n = 3.1 and 4) around T_p1 and T_p2, indicate that the bulk crystallization with a constant number of nuclei and with an increasing number of nuclei, respectively. The values of the local activation energy as a function of the fraction of crystallization (0.1 ≤ χ ≤ 0.9) decrease for the crystallization of LiBO₂ and EuTiO₃ and increase for the crystallization of Li₂B₄O₇. The values of n(χ) for T_p3 and T_p2 in the range (0.1 ≤ χ ≤ 0.9) and (0.1 ≤ χ ≤ 0.4), respectively, are larger than 4 indicate that the presence of anomalous in Avrami exponent. The trend of Judd-Ofelt intensity parameters (Ω₂ > Ω₄ > Ω₆) and the bonding parameter (δ) indicate that the lower symmetry and the highest covalent nature of the bonding around Eu³⁺ ions. (orig.)