The Migration Phenomenon of Metal Cations in Vein Quartz at Elevated Temperatures

With the rapid development of the photovoltaic (PV) and semiconductor fields, the reserves of traditional high-purity quartz raw materials can no longer meet the demands of various industries, creating an urgent need to develop new types of high-purity quartz feedstock. In this study, three groups of vein quartz samples from different mining areas were subjected to calcination at 950 °C for 2 h. The impurity states of the vein quartz before and after calcination were characterized using XRD, ICP, Raman and XRF. The migration behavior of metal cations in vein quartz under high-temperature conditions was systematically investigated, and the structural changes in the vein quartz before and after calcination were discussed from the perspectives of impurity element distribution and phase transformation. The results demonstrate that impurity cations in vein quartz migrate from the interior to the surface of the material under high-temperature environments. Quantitative ICP analysis of the inner and outer layers of the quartz samples before and after calcination revealed that, among the three groups, the surface impurity cation content of the sample with the most pronounced migration effect reached four times that of its internal structure. Combined with other characterization techniques, it was confirmed that after the cation migration process, the vein quartz samples exhibited a layered structure from the surface to the interior: a hematite mineralized layer, a high lattice impurity layer, and a low lattice impurity layer. This indicates that high-purity vein quartz with low lattice impurity content can be obtained by subjecting quartz to high-temperature calcination and subsequently removing the mineralized layer and the surface high lattice impurity layer. Consequently, vein quartz of ordinary quality can also be converted into high-purity quartz raw material of 4N grade or higher through the processes of cation migration and tailing removal.