ABSTRACT
Although some practical development of the metallurgical refining processes for solar grade silicon feedstock was started in the early 1980s (see Chapters 2, 3, and 4), fundamental information on thermodynamic properties of impurities in molten silicon was not available until research about this topic was started in Japan. Suzuki et al. [1-3] clarified the possibility of phosphorus removal by vacuum treatment and boron removal by slag treatment and Ar-H2O plasma oxidation processes, while
6.1 Thermodynamic Properties of Impurities in Molten Silicon ....................... 231 6.1.1 Boron ................................................................................................ 232 6.1.2 Phosphorus ........................................................................................ 233 6.1.3 Aluminum, Magnesium, and Calcium .............................................234 6.1.4 Titanium and Iron ............................................................................. 236 6.1.5 Interaction Parameters ...................................................................... 238
6.2 Solvent Refining ............................................................................................ 238 6.2.1 Thermodynamic Principles ..............................................................240 6.2.2 Si-Al Solvent Refining Test with Induction Heating ........................242 6.2.3 Silicon Crystal Growth in a Si-Al Solvent by Directional
Solidification ..................................................................................... 243 6.2.4 Solvent Purification and Combined Purification Processes .............245 6.2.5 Solvent with a High Vapor Pressure Component ............................. 247
6.3 Conclusions ...................................................................................................248 References ..............................................................................................................248
