Molybdenum foil plays a critical role in sapphire crystal growth furnaces due to its high melting point (2623°C), excellent high-temperature performance, and chemical stability, primarily used in reflective screens, cover plates, crucible linings, and support structures. Sapphire crystal growth (e.g., Kyropoulos or heat exchange methods) requires high temperatures (~2000°C), and molybdenum’s high melting point and creep resistance ensure structural stability under extreme conditions. Its low thermal expansion coefficient (4.8 × 10⁻⁶/K) matches sapphire’s (5-6 × 10⁻⁶/K), minimizing thermal stress and ensuring crystal quality. Thermal conductivity (138 W/m·K) promotes uniform heat distribution, optimizing growth. Typically high-purity (≥99.95%), with tensile strength of 500-700 MPa and hardness of 150-200 HV, it offers wear resistance for long-term use. Chemically, it is stable in vacuum or inert gases (e.g., argon), but oxidation above 600°C requires protection to prevent MoO₃ formation. Reflective screens reflect heat, reducing energy consumption; cover plates isolate atmospheres, protecting crystals; and supports ensure crucible stability. Cold-rolled foil (0.1-1 mm thick) provides high strength and smooth surfaces (roughness Ra<0.1 μm). Advantages include high-temperature stability and thermal compatibility; disadvantages are oxidation sensitivity and high cost. Quality control involves spectral analysis and mechanical testing to meet crystal growth standards.
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