Molybdenum crucible (or its reciprocal resistivity) depends on the purity, temperature and microstructure of molybdenum. As a metallic material, molybdenum has good conductivity and is suitable for high temperature applications that require conductive properties. The following is a detailed analysis of the conductivity of molybdenum crucible:
- Basic characteristics of conductivity
Room temperature conductivity:
high-purity molybdenum (99.95% or more) at room temperature (about 25°C) is about 18.7 × 10 ⁶ S/m (Siemens per meter), corresponding to a resistivity of 5.34 × 10 ⁻⁸ Ω· m (or 53.4 nΩ·m ).
This shows that molybdenum is a good conductor, but its conductivity is lower than that of copper (~58 × 10 ⁶ S/m) or silver (~63 × 10 ⁶ S/m).
- Effect of temperature on conductivity
As temperature increases, conductivity decreases:
As temperature increases, the resistivity of molybdenum increases (due to enhanced electron scattering), and the conductivity decreases accordingly. The following is a typical data of resistivity change with temperature:
25°C: Resistivity ~5.34 × 10 ⁻⁸ Ω· m, conductivity ~18.7 × 10 ⁶ S/m.
500°C: Resistivity ~20 × 10 ⁻⁸ Ω· m, conductivity ~5 × 10 ⁶ S/m.
1000°C: Resistivity ~35 × 10 ⁻⁸ Ω· m, conductivity ~2.86 × 10 ⁶ S/m.
1500°C: Resistivity ~50 × 10 ⁻⁸ Ω· m, conductivity ~2 × 10 ⁶ S/m.
2000° : Resistivity ~65 × 10 ⁻⁸ Ω· m, conductivity ~1.54 × 10 ⁶ S/m.
These values are based on high purity molybdenum; the conductivity of actual crucibles may vary slightly due to impurities or manufacturing processes.
- Factors affecting conductivity
purity:
High purity molybdenum has higher conductivity, and impurities (such as carbon, oxygen, and nitrogen) will increase resistivity and reduce conductivity.
Alloying:
The electrical conductivity of molybdenum alloys (such as Mo-W, Mo-La) is usually lower than that of pure molybdenum because the alloying elements introduce additional electron scattering.
Microstructure:
Forged, sintered or rolled molybdenum crucibles may have slightly varying conductivity due to grain size and defects.
temperature:
At high temperatures, lattice vibration and electron scattering are enhanced, resulting in a significant increase in resistivity and a decrease in conductivity.
- Practical application significance
High temperature conductivity:
Although the electrical conductivity of molybdenum decreases at high temperatures, it can still maintain ~1.5 × 10 ⁶ S/m at 2000°C, which is better than many high-temperature resistant materials (such as ceramic crucibles) and is suitable for processes that require conductive properties.
Typical applications:
Semiconductor manufacturing: In crystal growth or heat treatment, molybdenum crucibles can be used as conductive parts in conjunction with induction heating or electrode systems.
Vacuum furnace: Molybdenum crucible can be used for high temperature electric heating process in vacuum or inert atmosphere.
Arc Melting: Molybdenum ‘s electrical conductivity supports stable current conduction in arc or plasma processes.
Compared with other materials:
The electrical conductivity of molybdenum is higher than that of tungsten (~18.2 × 10 ⁶ S/m vs. ~10 × 10 ⁶ S/m at 25 ° C), but lower than that of copper or silver.
Compared to ceramics (such as alumina, which has a conductivity close to zero), molybdenum ‘s electrical conductivity is a significant advantage.
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