Novel and efficient purification of silicon through ultrasonic-Cu catalyzed chemical leaching.

The present study proposed a novel and efficient ultrasonic-Cu catalyzed chemical leaching (U-CuCCL) method to purify large-sized industrial silicon powders. Different from the traditional ultrasonic-HF (U-HF) leaching method, U-CuCCL and U-CuCCL combined rapid thermal processing (U-CuCCL + RTP) were performed to investigate the efficiency of removing the main impurities Fe, Al, Ca, Ti, Ni, V, Cu, and Mn. The evolution of typical precipitates phases on the surface of silicon before and after leaching were observed and analyzed by electron probe micro analyzer. The results show that the impurities removal can be significantly improved under the ultrasonically strengthen process, especially the U-CuCCL process shows a high-efficient impurities removal efficiency. After the U-CuCCL, the etched silicon powders accompanied with numerous porous structure are obtained which is beneficial for the removal of impurities. Notably, it was found that the rapid thermal processing is beneficial for the residual impurities diffuse to the porous layer surface and the purity of silicon powder can be significantly increased from 99.3% to 99.995%.