Silicon nitride powder for solar polysilicon ingot casting and preparation method thereof

Abstract

The invention relates to a silicon nitride powder for solar polysilicon ingot casting and a preparation method thereof. The silicon nitride powder for solar polysilicon ingot casting comprises 25-50wt.% of ganister sand, 40-65 wt.% of a diluent and 5-15 wt.% of an additive. The method is not only simple in preparation process, free of any toxic and harmful gases, and applicable to mass production, but also prepares a high thermal conductivity high purity turquoise silicon carbide powder containing trace silicon nitride powder by controlling the reaction parameters through a one-step reaction. The silicon carbide powder is conducive to the determination of coating uniformity in a spraying process; while the trace silicon carbide contained in the coating improves the thermal conductivity of the coating, provides homogeneous nucleation points, and is beneficial for heterogeneous nucleation, orientated growth of polycrystalline, and improvement of film formation rate.

Description

technical field [0001] The invention relates to silicon nitride powder for solar polysilicon ingot casting and a preparation method thereof, belonging to the technical field of inorganic non-metallic materials. Background technique [0002] Polysilicon ingot casting is a very important basic process in the entire photovoltaic industry chain. The quality of the cast silicon ingot directly affects the photoelectric conversion efficiency of solar cells. Silicon nitride is widely used as a release agent in the polysilicon ingot casting process due to its excellent high temperature resistance, high chemical stability, and small thermal expansion coefficient. It is an indispensable part of the ingot casting process. , to better block the contamination of silicon ingots by oxygen and other impurities. [0003] The preparation methods of silicon nitride powder that have been researched and developed at present include: direct silicon powder nitriding method, carbothermal reduction ...

AI Technical Summary

Problems solved by technology

However, the toxic and harmful gases hydrogen chloride and hydrogen fluoride produced during the decomposition of ammonium halide not only endanger human health, but also cause a certain degree of corrosion to equipment and workshops, and the process of post-processing tail gas increases production costs.

[0004] At present, silicon nitride on the market is white or off-white powder. In the process of spraying the quartz crucible, the inner wall of the crucible is also white, and the coating thickness is relatively thin, only 10-1500 μm. If the coverage is not dense, such defects are not easy to be found by the naked eye, resulting in direct contact between the silicon melt and the quartz crucible during the ingot casting process, which not only affects the demoulding effect of the silicon ingot and causes "sticking", but also reduces the purity of solar polysilicon , will cause serious safety accidents

In addition, although pure silicon nitride coating has been widely used as a release agent, its thermal conductivity is low (theoretical value is 25W / (m*k)), which is not conducive to heat conduction, and has strict requirements on thermal field distribution. The polycrystalline silicon ingot casting process is not favorable, and it is easy to cause the temperature gradient difference in the same plane in the crucible, the nucleation cannot be controlled, the generation of dislocations leads to poor crystal directional growth, and the thermal stress caused by large lateral and longitudinal temperature differences It is very likely to cause the silicon ingot to break, which will affect the yield

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