Preparation of 6N,7N High-Purity Gallium by Crystallization: Process Optimization

Area of Science:

• Materials Science
• Crystallography
• Chemical Engineering

Background:

• Gallium purification is crucial for advanced electronic applications.
• Achieving ultra-high purity levels (6N and 7N) presents significant challenges.
• Existing purification methods may lack efficiency or scalability.

Purpose of the Study:

• To develop an induction-assisted radial crystallization method for ultra-high purity gallium crystal seed preparation.
• To investigate and optimize key process parameters for gallium purification.
• To establish effective purification schemes for achieving 6N and 7N gallium.

Main Methods:

• Radial crystallization purification under induction.
• Systematic variation of cooling temperature, cooling water temperature, flow rate, and crystal seed amount.
• Experimental determination of the governing equation for crystallization rate.
• Proposal and testing of three distinct purification schemes.

Main Results:

• Optimized parameters: 278 K crystal seed prep temp, 293 K cooling water temp, 40 L·h⁻¹ cooling water flow rate, and six crystal seeds.
• Crystallization rate showed a linear decrease with increasing cooling water temperature and an exponential increase with increasing cooling water flow.
• Scheme I yielded 6N gallium from 4N crude gallium; Schemes II and III yielded 7N gallium.
• Achieved purities: 99.999987% (Scheme I), 99.9999958% (Scheme II), and 99.9999958% (Scheme III).

Conclusions:

• The induction-assisted radial crystallization method is effective for producing ultra-high purity gallium.
• The study identified optimal parameters and established governing equations for crystallization rate.
• The proposed purification schemes successfully demonstrated the capability to produce 6N and 7N gallium.