Applications of Molybdenum Sheet in Sapphire Crystal Growth Furnaces

The growth of sapphire crystals requires high temperatures and a clean environment, making molybdenum sheet, with its unique physicochemical properties, an indispensable key material in sapphire crystal growth furnaces.

Molybdenum sheet primarily serves three core functions in sapphire growth furnaces—structural support, thermal management, and corrosion resistance—playing a critical role across key furnace components:

Structural Support: Molybdenum sheet is used as components for crucible support and structure, ensuring the stability of the crucible during crystal growth. Specifically, molybdenum sheet is processed into circular trays of a certain thickness to bear the weight of crucibles ranging from tens to hundreds of kilograms, withstanding high-temperature gravitational loads to prevent deformation. Molybdenum sheet brackets are employed to secure moving parts like crucible lifting systems and seed rods, maintaining dimensional accuracy under high temperatures.

Thermal Management and Insulation: Molybdenum sheet acts as components for heat field regulation and insulation, aiding in controlling the temperature distribution within the furnace to ensure uniform sapphire crystal growth. Processed into multi-layered cylindrical insulating screens of a specific thickness, molybdenum sheet surrounds the crucible, reflecting thermal radiation to reduce heat loss. Baffles made from molybdenum sheet are placed above the crucible to adjust the heat flow distribution on the melt surface, suppressing contamination of the seed crystal by volatile Al₂O₃ vapor. Perforated or stepped molybdenum sheet at different furnace heights modifies heat conduction paths, precisely controlling the temperature gradient at the solid-liquid interface.

Corrosion Resistance and Oxidation Prevention: Molybdenum sheet serves as components to prevent corrosion and oxidation, avoiding contamination of the sapphire melt. Molybdenum sheet guide cylinders direct the flow of inert gas, preventing oxygen from entering the furnace chamber and causing crucible oxidation. Collection trays made from molybdenum sheet are installed at the top or sides of the furnace to capture volatilized Al₂O₃ particles from the melt, preventing their condensation on furnace walls or seed crystals, which could introduce impurities.

Molybdenum sheet used in sapphire growth furnaces is typically of high-purity grade (purity ≥99.95%), with strict control of impurities (e.g., Fe, Cu, Si ≤10 ppm) to avoid contaminating the melt. For instance, Fe impurities entering the sapphire crystal can form color centers, affecting optical uniformity.

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