Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 4, pp. 493−497.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © V.M. Borshchev, A.N. D’yachenko, A.D. Kiselev, R.I. Kraidenko, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 4,
AND INDUSTRIAL INORGANIC CHEMISTRY
Production of Silicon from Magnesium Silicide
V. M. Borshchev, A. N. D’yachenko, A. D. Kiselev, and R. I. Kraidenko
Tomsk National Research Polytechnic University, Tomsk, Russia
Received September 17, 2012
Abstract—Kinetic methods and thermogravimetry were used to study the oxidation process of magnesium silicide
in air in the temperature range 300–1000°C. The reaction products were identiﬁ ed by X-ray phase analysis. It was
found that the reaction occurs in the temperature range 510–710°C to give silicon and magnesium oxide. With the
temperature increasing further, silicon is oxidized to silicon dioxide.
The conventional techniques for manufacture of
silicon for solar power engineering include a number
of stages in which silicon-containing raw materials
are puriﬁ ed to remove interfering impurities and then
elementary silicon is obtained [1, 2].
Despite being widely used and well developed,
methods for production of polycrystalline silicon
from metallurgical silicon are technically complex,
require substantial capital investment for setting-up
production plants, and gross maintenance expenditure
in manufacture of commercial products.
Alternative technologies, such as production of
silicon from special-purity quartz by its reduction and
subsequent additional puriﬁ cation occupy a rather small
part of the market; however, the share of polycrystalline
silicon produced by these techniques steadily grows
A method is known for production of silicon by
magnesiothermic reduction of silicon dioxide, followed
by separation of reaction products . Silicon and
magnesium oxide are separated by acid leaching
with hydrochloric acid. Together with dissolution of
magnesium oxide, there occurs decomposition of the
silicide to give silane (SiH
) vapor. Interacting with
water contained in hydrochloric acid, silane self-ignites
with explosive blasts. In the end, SiO
is again formed.
A loss of this kind is inadmissible in reduction of the
pure and rather expensive oxide.
The reduction product is the three-component system
composed of silicon, magnesium oxide, and magnesium
2Mg + SiO
= 2MgO + Si, (1)
4Mg + SiO
= 2MgO + Mg
2Mg + Si = Mg
To remove magnesium silicide, it is suggested to
subject magnesiothermy products to thermal calcination
in air. The separation is based on the reaction of
magnesium silicide with oxygen to give magnesium
oxide and silicon. In this way, it is possible to provide
the maximum recovery of silicon from silicon dioxide
and to preclude any loss of silicon.
The goal of the present study was to examine the
interaction of magnesium silicide with oxygen and to
identify reaction products.
Thermodynamic calculations of the decomposition of
magnesium silicide were performed for the temperature
range 298–900 K  (Table 1). The equilibria of
chemical reactions (4)–(7) were found by the Temkin–
Si + O
= 2MgO + Si, (4)
Si + 2O
Si + 2O
= 2MgO + MgSiO
Si + 2O
= 2MgO + SiO