higher field strength cation such as Al3+ exhibit higher activation for crystallization followed by other cations as Y3+ and La3+. The field strength of Al3+ which act as intermediate is highest and due to this it holds the glass matrix tightly. Because of this fact it requires higher activation energy for crystallization as compared to the Y3+ cation followed by La3+ which has the least value of field strength [20]. Moreover, Al2O3 addition in glass is well known to prevent the crystallization and control the viscosity of the glasses