Study of CdTe single crystal growth by using the ground mirror apparatus of high temperature materials rack on China space station

To evaluate the capability of the ground mirror apparatus of High Temperature Materials Rack (HTMR) in reproducing the thermal-fluid environment of spatial crystal growth and supporting diverse processing requirements, this study conducted growth experiments and numerical simulations of Cadmium Telluride(CdTe) single crystals with varying diameters (14 mm and 20 mm). The objective was to verify the apparatus's applicability across different crystal specifications through size effect analysis. Under identical processing conditions, complete crystal ingots were successfully obtained. Leveraging the exceptional thermal stability of the HTMR, the study effectively eliminated random thermal perturbations, enabling precise capture of the impact of size variations on crystal quality. Experimental characterization revealed that the 14 mm crystal exhibited superior crystalline quality with uniform inclusion distribution and consistent orientation. In contrast, the 20 mm crystal, influenced by size effects, showed enrichment of internal defects, degraded infrared transmission, and distinct subgrain splitting. Numerical simulations further elucidated the underlying mechanisms from a thermal-fluid coupling perspective: the increased radial temperature gradient and decreased solid-liquid interface stability associated with larger diameters are the primary drivers of quality fluctuations. The high consistency between multi-scale characterization and simulation predictions not only reveals the patterns of size effects but also confirms the HTMR’s capacity for accurate reproduction of thermal-fluid field characteristics and its processing versatility for space high-temperature material racks. This provides a robust ground-based verification foundation for future large-scale, high-quality single crystal growth missions on the space station.