The Physical And Chemical Basic Research Of SiC Single Crystal Prepared By Rare Earth Metal Co-solvent Method

The cosolvent method can grow high-quality SiC single crystal with fewer defects such as micropipes and dislocations at low temperatures.In this paper,physical and chemical studies on the fabrication of SiC single crystal using rare earth metals as cosolvents were carried out.In addition,taking the synthesis and separation of Nd-Sialloy as an example,the feasibility of fabricating REs-Si?REs is a rare earth?alloy from silicon reducing rare-earth oxide to grow SiC single crystal was studied,and solved the problem of recycling of REs-Sialloy after growing SiC single crystal with REs-Simelt.The main conclusions are as follows:1.When Lais used as a co-solvent,The results of phase analysis in the sample after liquid-solid equilibrium show that:Among the components melt on the side with low Prcontents in the liquid phase region of the Pr-Sibinary system,SiC is the only stable Carbon-containing phase.It is concluded that at 1723K and 1823K,when the contents of Lain the La-Simelt is lower than 20 at.% and 25 at.%,respectively,the La-Simelt is suitable for growing SiC single crystal.On the side where the Lacontents in the La-Sibinary system liquid phase is high,it is found that the C-containing compound saturated and stable in the La-Simelt is La₂C₃ or LaC₂.So,those composition La-Simelt are not suitable to grow SiC single crystal.2.When Pris used as a co-solvent,The results of phase analysis in the sample after liquid-solid equilibrium show that:Among the components melt on the side with low Prcontents in the liquid phase region of the Pr-Sibinary system,SiC is the only stable Carbon-containing phase.It is concluded that at 1723K and 1823K,when the contents of Prin the Pr-Simelt is lower than 21 at.%and 25 at.%,respectively,the Pr-Simelt is suitable for growing SiC single crystal.On the side where the Lacontents in the Pr-Sibinary system liquid phase is high,it is found that the C-containing compound saturated and stable in the Pr-Simelt is Pr₂C₃ or PrC₂.So,those composition Pr-Simelt are not suitable to grow SiC single crystal.3.Determinated the solubility of C in La-Simelt and Pr-Simelt by liquid-solid equilibrium method,and combined with the analysis results of the equilibrium phase,the ternary isothermal phase diagrams of La-Si-C and Pr-Si-C were drawn,finally.It was found that the optimal melt components for growing of SiC single crystal with La-Sias the melt are Si-20 at.%Laand Si-25 at.%Laat 1723K and 1823K,respectively,and the corresponding C solubility are 6.06 at.%and 10.41 at.%.At1723K and 1823K,the optimal melt composition for growing SiC single crystal with Pr-Sias the melt is Si-21 at.%Prand Si-25 at.%Pr,respectively,and the corresponding C solubility is 8.38 at%and 7.62 at.%.4.The study results of siliconthermal reducing of Nd₂O₃showed that silicon can reduce most of the Nd?the maximum reduction rate is 87.43 wt.%?in Nd₂O₃to obtain Nd-Sialloy.Nd and Siin Nd-Sialloy can be separated by hydrometallurgy process technology to achieve the recyclable use of Nd-Sialloy.However,because the solubility of C in the Nd-Simelt is extremely low,the Nd-Sialloy obtained by this method cannot be used to grow SiC single crystal.Although the experiments confirmed that the REs-Sialloy prepared by silicon reduced rare earth oxide cannot be used to grow SiC single crystal,when the pure rare earth and pure silicon synthetic alloy melt is used to grow SiC single crystal,the hydrometallurgy technology in this paper can still be used to recovers REs and Si in REs-Sialloys.