Effect of lithium chloride on crystallization process of neodymium disilicate

Tetragonal neodymium disilicate (i.e., Nd2Si2O7) powder was synthesized in the absence and presence of 5 wt% lithium chloride (i.e., LiCl) as a mineralizer by sol-gel method and subsequent thermal treatment process. The effect of LiCl on the crystallization process of the synthesized xerogel was investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The crystallization kinetic was analyzed at different heating rates (i.e., 2, 5, 10 and 20 K/min) by a non-isothermal differential thermal analysis method. The activation energies of the tetragonal Nd2Si2O7 crystallization calculated by the Kissinger and the Ligero methods are 673 kJ/mol for the xerogel without LiCl and 586 kJ/mol for the xerogel with 5 wt% LiCl. In addition, the crystallization mechanism was also discussed, indicating that the crystallization mechanism of the tetragonal Nd2Si2O7 changes from bulk and homogeneous to two-dimension crystallization in the presence of 5 wt% LiCl.