Effect of Ti addition to Cu-Si alloy on the boron distribution in various phases

Huang, Liuqing; Chen, Juan; Danaei, Abdolkarim; Thomas, Sridevi; Huang, Lin; Luo, Xuetao; Barati, Mansoor

doi:10.1016/j.jallcom.2017.10.279

Cited by 15 publications

(9 citation statements)

References 32 publications

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“…Figure 5a− 5e, which supports the existence of a stable TiB 2 phase. 52 According to the calculation results in Figure 3, it can be known that the TiB 2 phase began to separate out at 1200 °C in The HTXRD results are in good agreement with the calculated results shown in Figure 3. Figure 5e is from the in situ observation results of the HT-LCSM, which can more intuitively present the precipitation process of the TiB 2 phase at the solidification front of the Al−Si alloy.…”

Section: Resultssupporting

confidence: 75%

“…In addition, the peak s at a binding energy of 98.1 eV corresponds to the 2p 3/2 peak of Si, and 73.7 eV corresponds to the 2p 3/2 peak of Al, and the presence of Si and Al is not surprising since the chemical reconstruction of Ti and B is done in Al–Si alloys, as shown in Figure c,d. TiB 2 has a hexagonal structure with lattice parameters of a = 0.3028 nm, b = 0.3028 nm, and c = 0.3228 nm, as shown in the following Figure e, which supports the existence of a stable TiB 2 phase …”

Section: Resultssupporting

confidence: 58%

“…In the past 5 years, this aspect of the work has been widely concerned. A small amount of Ti (<2037 ppm) was employed as an additive to enhance B removal from Si in electromagnetic solidification refining with an Al–Si alloy, and the residual B in the refined Si could be removed to 1.2 ppm; copper was chosen as the primary solvent, and a small amount of Ti was added to the Si–Cu alloy to enhance the extraction of certain B, where the B content decreased from 15 to 2.3 ppm; Zr was selected as an impurity modifier for the chemical reconstruction of B in the Al–Si alloys. The thermodynamic calculation results showed that the content of solid solution B in silicon can be reduced to less than 2 ppm at a temperature of 973 K when the content of Zr exceeds 500 ppm .…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Enhanced In Situ Separation of Boron at the Silicon Alloy Solidification Interface through Innovating the Impurity Chemical Reconstruction Approach for SoG-Si

Qian

Zhou

et al. 2021

ACS Sustainable Chem. Eng.

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Removal of trace impurities such as boron (B) and phosphorus (P) has always been a challenge for the preparation of solar-grade silicon (SoG-Si). Chemical reconstruction has been thought to be an effective way to remove trace impurities by changing the phase structure and location of impurities. The traditional way of the chemical reconstruction of impurities at the grain boundary after solidification inevitably relies on the subsequent separation of crystalline Si and chemical reconstruction medium. Thus, we develop a new method for the chemical reconstruction of B at the front of the solidification interface of the Si alloy, which provides advantages for the in situ separation of the reconstructed impurity phase in the supergravity filtration separation process. The chemical reconstruction of B at the solidification front of the Si alloy has been realized by adding 25–75% of the liquation agent aluminum (Al) and about 10 000 ppm of the impurity modifier agent titanium (Ti) with the help of Thermo-Calc thermodynamic calculation and experimental verification. The influence mechanism of the supergravity field on the precipitation behavior of the chemically reconstructed phase TiB2 is revealed by the derived Maxwell–Stefan (MS) equation under the action of the supergravity field. A special filter-type combined crucible is skillfully designed and strictly controlled to cool the crucible containing the alloy melt at a constant temperature gradient under the supergravity field to achieve in situ separation of impurities at the solid–liquid interface of the Si alloy. The chemical reconstruction phase TiB2 is mainly retained on the surface of crystalline Si during the process of supergravity centrifugal filtration, which is more suitable for the deep removal of the B impurity and B content in Si drops below 1.5 ppm by simple pickling. In addition, the Si–Al–(Ti) alloy with a small amount of impurities obtained after centrifugal filtration separation can be further used for the chemical reconstruction of impurities, and the recycling of chemical reconstruction medium has been achieved. The present work proposes a new idea of chemical reconstruction of impurities at the front of alloy solidification and in situ separation, which expands the way of in situ separation of trace impurities at the solid–liquid interface of the alloy.

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Section: Resultssupporting

confidence: 75%

Section: Resultssupporting

confidence: 58%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Enhanced In Situ Separation of Boron at the Silicon Alloy Solidification Interface through Innovating the Impurity Chemical Reconstruction Approach for SoG-Si

Qian

Zhou

et al. 2021

ACS Sustainable Chem. Eng.

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“…It should be noted that during the solvent refining process, if the B-removal process can be improved by utilizing small amounts of additives that have strong affinity toward B, thus to enhance the formation of intermetallic compounds (borides), it would become more effective and practical. It has been proven by Yoshikawa and Huang that titanium (Ti) works as such an additive both in the Si–Al and Si–Cu melts, forming the TiB 2 intermediate compound that is thermodynamically stable. Furthermore, the zirconium (Zr) additive has been verified by Lei as a more effective one in enhancing B-removal efficiency than the Ti additive in Si–Al melts.…”

Section: Introductionmentioning

confidence: 99%

Low-Temperature Process for the Fabrication of Low-Boron Content Bulk Si from Si–Cu Solution with Zr Addition

Ren

Morita

2020

ACS Sustainable Chem. Eng.

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A novel approach was put forward to remove B from Si by utilizing Zr as an additive during solidification, whereby, using the Si–Cu solvent, bulk Si with large area and low boron content was obtained. The premise of this work is based on the following parameters: (i) the lower liquidus temperature of the Si–Cu system; (ii) the notable density difference between solid Si and liquid Si–Cu; (iii) the low solubility of Cu in solid Si; and (iv) the strong affinity of Zr for B, enhancing boride formation. The experimental results show that (i) intermediate ZrB2 compounds were found at the bottom of the sample; (ii) the B-removal fraction improved significantly, the highest of which was 93.4%; (iii) large areas of bulk Si were obtained, and a high Si enrichment percentage of 99.2% was achieved; (iv) the residual Cu content was reduced to a relatively low level, the molar fraction of which ranged from 0.00099 to 0.00191; and (v) the Zr additive was completely removed and did not pollute the refined Si. This one-step directional solidification process provides a better alternative for Si-based solvent refining to produce solar-grade silicon for use in the photovoltaic industry.

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“…The Siemens method as the main technology is not environmentally friendly, resulting in considerable pollution. In order to obtain low energy consumption and clean production, and improve the removal efficiencies of impurities, a series of purification methods of SoG-Si from MG-Si, such as solvent refining [5,6], directional solidification [7][8][9], slag refining [10,11], electron beam melting treatment [12], and plasma treatment [13] etc. have been investigated.…”

Section: Introductionmentioning

confidence: 99%

Separation and Recovery of Refined Si from Al–Si Melt by Modified Czochralski Method

Lin

et al. 2020

Materials

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Separation of refined silicon from Al–Si melt is still a puzzle for the solvent refining process, resulting in considerable waste of acid and silicon powder. A novel modified Czochralski method within the Al–Si alloy is proposed. After the modified Czochralski process, a large amount of refined Si particles was enriched around the seed crystalline Si and separated from the Al–Si melt. As for the Al–28%Si with the pulling rate of 0.001 mm/min, the recovery of refined Si in the pulled-up alloy (PUA) sample is 21.5%, an improvement of 22% compared with the theoretical value, which is much larger 1.99 times than that in the remained alloy (RA) sample. The content of impurities in the PUA is much less than that in the RA sample, which indicates that the modified Czochralski method is effective to improve the removal fraction of impurities. The apparent segregation coefficients of boron (B) and phosphorus (P) in the PUA and RA samples were evaluated. These results demonstrate that the modified Czochralski method for the alloy system is an effective way to enrich and separate refined silicon from the Al–Si melt, which provide a potential and clean production of solar grade silicon (SoG-Si) for the future industrial application.

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Effect of Ti addition to Cu-Si alloy on the boron distribution in various phases

Cited by 15 publications

References 32 publications

Enhanced In Situ Separation of Boron at the Silicon Alloy Solidification Interface through Innovating the Impurity Chemical Reconstruction Approach for SoG-Si

Enhanced In Situ Separation of Boron at the Silicon Alloy Solidification Interface through Innovating the Impurity Chemical Reconstruction Approach for SoG-Si

Low-Temperature Process for the Fabrication of Low-Boron Content Bulk Si from Si–Cu Solution with Zr Addition

Separation and Recovery of Refined Si from Al–Si Melt by Modified Czochralski Method

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