Migration Mechanisms of Al³⁺/Li⁺ Lattice Impurities during Phase Transition from -Quartz to -Quartz: An Implication for Purification of High-Purity Quartz

The quality of high-purity quartz (HPQ) that used in strategic industries is normally limited due to lattice impurities. In order to reveal the migration pathway of lattice impurities in quartz particles during phase transition from alpha-quartz to beta-quartz, alpha-quartz and Al3+/Li+-substituted alpha-quartz (S-alpha-quartz) was investigated under 846.15 K and 101.325 kPa based on density functional theory. Results showed that beta-quartz exhibited more interstitial volume, dominating the migration of lattice impurities. This further indicates that the phase transition process was beneficial for the migration of lattice impurity from a structural point of view. Moreover, Al3+ and Li+ mainly migrated from the intracell to lattice surface along the c axis. In addition, Li+ migrated more easily than Al3+ due to higher mean square displacement values. From a thermodynamic point of view, the lower energy barrier in the case of the Al3+ and Li+ lattice suggested that the presence of lattice impurities promoted phase transition. This study therefore provides an excellent theoretical basis for the removal of lattice impurities of HPQ from an atomic perspective, for the first time.