The invention provides a method for purifying silicon by means of a phase separation dealloying reaction, including: mixing a silicon raw material containing metallic or non-metallic impurities with magnesium powder first and then fully reacting under an inert atmosphere so as to obtain a first product; placing the first product in a nitrogen-containing atmosphere to undergo a nitriding reaction to form three-dimensional porous silicon and magnesium nitride distributed in pore channels thereof so as to obtain a second product, the impurities further being separated during the precipitation and crystallization of silicon, and being dissolved in the liquid-phase magnesium nitride; treating the second product by using acid-pickling, the magnesium nitride and impurities being dissolved and converted into a solution, and a solid product being high-purity porous silicon.

Technical-grade silicon is produced by reacting a raw material mixture containing silicon dioxide and carbon in an electric furnace with a particulate mediator containing at least one of the elements C, O, Al and Si is reacted in an electric furnace, wherein the mixture is described by a dimensionless index K, K having a value of from 0 to 745 and being calculated as follows:

[00001]$\begin{array}{cc}K={\omega }_M.Math.{\beta }_{RM}.Math.{\mu }_C\mathrm{where}\text{:}& \mathrm{equation}\left(1\right)\\ {\omega }_M=\frac{6.Math.\left(1-{\mathrm{.Math.}}_{m,M}\right)}{d_{50,M}}& \mathrm{equation}\left(2\right)\\ {\beta }_{RM}=d_{90,RM}-d_{10,RM}& \mathrm{equation}\left(3\right)\\ {\mu }_C=\frac{3}{2}-\frac{m_M}{m_{RM}}& \mathrm{equation}\left(4\right)\end{array}$

In a step of performing cylindrical grinding of a polycrystalline silicon bar 10 grown by a Siemens method, this cylindrical grinding step is performed such that a polycrystalline silicon rod 30, whose center axis C.sub.R is shifted from a center axis C.sub.0 of a silicon core wire 20 by 2 mm or more, is manufactured.

Technical silicon is produced by heating a raw material mixture comprising particulate silicon metal-containing material and a particulate mediator containing at least one of C, O, Al, Ca and Si, to at least 1490° C., forming a liquid silicon phase, and solidifying this phase, wherein the raw material mixture a characteristic number K of from 0.000 to 60, calculated as follows:

[00001]$\begin{array}{cc}K=\frac{m\left(\mathrm{SiM}\right).Math.d50\left(\mathrm{SiM}\right)+m\left(\mathrm{Med}\right).Math.d50\left(\mathrm{Med}\right)}{m\left(\mathrm{SiM}\right)+m\left(\mathrm{Med}\right)}.Math.\phi & \left(\mathrm{equation}1\right)\end{array}$

where m (SiM) is the mass of the silicon metal-containing material in the batch m (Med) is the mass of the mediator d.sub.50,SiM is the mean particle size of the silicon metal-containing material, d.sub.50,Med is the mean particle size of the mediator, and φ is the mean porosity of the silicon metal-containing material.+

Technical silicon is produced by heating a raw material mixture comprising particulate silicon metal-containing material and a particulate mediator containing at least one of C, O, Al, Ca and Si, to at least 1490° C., forming a liquid silicon phase, and solidifying this phase, wherein the raw material mixture a characteristic number K of from 0.000 to 60, calculated as follows:

[00001]$\begin{array}{cc}K=\frac{m\left(\mathrm{SiM}\right).Math.d50\left(\mathrm{SiM}\right)+m\left(\mathrm{Med}\right).Math.d50\left(\mathrm{Med}\right)}{m\left(\mathrm{SiM}\right)+m\left(\mathrm{Med}\right)}.Math.\phi & \left(\mathrm{equation}1\right)\end{array}$

where m (SiM) is the mass of the silicon metal-containing material in the batch m (Med) is the mass of the mediator d.sub.50,SiM is the mean particle size of the silicon metal-containing material, d.sub.50,Med is the mean particle size of the mediator, and φ is the mean porosity of the silicon metal-containing material.+

The present invention relates to a silicon powder, where the size of the silicon powder particles are between 3 and 30 μm, a particle size fraction D10 of the silicon powder particles is between 3 and 9 μm, and where the silicon powder particles have no, or substantially no, silicon particles with a size smaller than D10 attached to the surface. The silicon powder according to the present invention is produced by wet classifying produced silicon powders.

The present invention relates to a silicon powder, where the size of the silicon powder particles are between 3 and 30 μm, a particle size fraction D10 of the silicon powder particles is between 3 and 9 μm, and where the silicon powder particles have no, or substantially no, silicon particles with a size smaller than D10 attached to the surface. The silicon powder according to the present invention is produced by wet classifying produced silicon powders.

A polycrystalline silicon crushed lump has a surface metal concentration of 15.0 pptw or less, in which a copper concentration is 0.30 pptw or less in the surface metal concentration, and a total concentration of iron and zinc is 2.00 pptw or less in the surface metal concentration, and preferably an iron concentration is 1.25 pptw or less, and a zinc concentration is 0.75 pptw or less.

A polycrystalline silicon crushed lump has a surface metal concentration of 15.0 pptw or less, in which a copper concentration is 0.30 pptw or less in the surface metal concentration, and a total concentration of iron and zinc is 2.00 pptw or less in the surface metal concentration, and preferably an iron concentration is 1.25 pptw or less, and a zinc concentration is 0.75 pptw or less.

A method for manufacturing polycrystalline silicon fragments includes producing a polycrystalline silicon rod by the Siemens method; crushing the polycrystalline silicon rod to obtain polycrystalline silicon fragments; and cleaning by etching the polycrystalline silicon fragments in a cleaning tank. In the cleaning, small pieces of the polycrystalline silicon having controlled shapes and sizes are present in the cleaning tank and the weight change of the small pieces of the polycrystalline silicon before and after the etching is measured to thereby manage the cleaning.