Provided is a silicon-based molten composition including silicon, carbon, and a metal in which a solubility parameter (C.sub.si.sup.sol) defined by Equation (1) below is less than 0.37, wherein a SiC single crystal is formed by a solution method:
C.sub.si.sup.sol=AB+.sub.1.sub.2Equation (1)
in Equation (1) above, A is a first energy (A) of a first evaluation lattice including silicon atoms, a carbon atom, and metal atoms in a silicon crystal lattice including metals and carbons, B is a second energy (B) of a second evaluation lattice including silicon atoms and metal atoms in a silicon crystal lattice including metals, 1 is a constant of 5.422, and 2 is a constant of 9.097.

Provided is a silicon-based molten composition including silicon, carbon, and a metal in which a solubility parameter (C.sub.si.sup.sol) defined by Equation (1) below is less than 0.37, wherein a SiC single crystal is formed by a solution method:
C.sub.si.sup.sol=AB+.sub.1.sub.2Equation (1)
in Equation (1) above, A is a first energy (A) of a first evaluation lattice including silicon atoms, a carbon atom, and metal atoms in a silicon crystal lattice including metals and carbons, B is a second energy (B) of a second evaluation lattice including silicon atoms and metal atoms in a silicon crystal lattice including metals, 1 is a constant of 5.422, and 2 is a constant of 9.097.

A silicon-based molten composition according to an exemplary embodiment is used in a solution growing method for forming a silicon carbide single crystal, includes silicon (Si), yttrium (Y), and iron (Fe), and is expressed in Formula 1.

Si.sub.aY.sub.bFe.sub.c [Formula 1] In Formula 1, the a is equal to or greater than 0.4 and equal to or less than 0.8, the b is equal to or greater than 0.2 and equal to or less than 0.3, and the c is equal to or greater than 0.1 and equal to or less than 0.2.

The present invention relates to a silicon-based molten composition for forming a SiC single crystal by a solution method, the composition containing silicon, carbon, and a metal satisfying 0.70Csisol1.510 with respect to a solubility parameter (Csisol) defined by the following Equation (1):
Csisol=AB+12Equation (1) wherein, A is first energy (A) of a first evaluation lattice containing silicon atoms, carbon atoms, and metal atoms, in a silicon crystal lattice containing the metal and the carbon; B is second energy (B) of a second evaluation lattice containing silicon atoms and metal atoms, in a silicon crystal lattice containing the metal; 1 is 5.422 as a constant value, and 2 is 9.097 as a constant value.

The present invention relates to a silicon-based molten composition for forming a SiC single crystal by a solution method, the composition containing silicon, carbon, and a metal satisfying 0.70Csisol1.510 with respect to a solubility parameter (Csisol) defined by the following Equation (1):
Csisol=AB+12Equation (1) wherein, A is first energy (A) of a first evaluation lattice containing silicon atoms, carbon atoms, and metal atoms, in a silicon crystal lattice containing the metal and the carbon; B is second energy (B) of a second evaluation lattice containing silicon atoms and metal atoms, in a silicon crystal lattice containing the metal; 1 is 5.422 as a constant value, and 2 is 9.097 as a constant value.

An oxychloride infrared nonlinear optical crystal and the preparation method and use thereof, the optical crystal has a general chemical formula of Pb.sub.2+xOCl.sub.2+2x, therein 0<x<0.139 or 0.141<x<0.159 or 0.161<x0.6. The crystal is non-centrosymmetric, belongs to orthonormal system with space group of Fmm2, cell parameter is a=35.4963(14)0.05 , b=5.8320(2)0.05 , c=16.0912(6)0.05 . The crystal is prepared by high temperature melt method or flux method. The crystal has a strong second harmonic generation efficiency of 4 times that of KDP (KH.sub.2PO.sub.4) tested by Kurtz method, it is phase machable, transparent in the range of 0.34-7 m. The laser damage threshold is 10 times that of the current commercial infrared nonlinear optical crystal AgGaS.sub.2. No crystalline water exists in lead oxychloride, and it is stable in the air and has good thermal stability.

An oxychloride infrared nonlinear optical crystal and the preparation method and use thereof, the optical crystal has a general chemical formula of Pb.sub.2+xOCl.sub.2+2x, therein 0<x<0.139 or 0.141<x<0.159 or 0.161<x0.6. The crystal is non-centrosymmetric, belongs to orthonormal system with space group of Fmm2, cell parameter is a=35.4963(14)0.05 , b=5.8320(2)0.05 , c=16.0912(6)0.05 . The crystal is prepared by high temperature melt method or flux method. The crystal has a strong second harmonic generation efficiency of 4 times that of KDP (KH.sub.2PO.sub.4) tested by Kurtz method, it is phase machable, transparent in the range of 0.34-7 m. The laser damage threshold is 10 times that of the current commercial infrared nonlinear optical crystal AgGaS.sub.2. No crystalline water exists in lead oxychloride, and it is stable in the air and has good thermal stability.

A SiC single crystal is prepared by the solution process of placing a seed crystal in contact with a SiC solution in a crucible and letting a SiC single crystal to grow from the seed crystal. The method includes the first growth step of conducting crystal growth using (0001) or (000-1) plane of a SiC single crystal of which the seed crystal is composed, as the growth surface, and the second growth step of conducting crystal growth using (1-100) or (11-20) plane of a SiC single crystal resulting from the first growth step as the growth surface. A SiC single crystal of high homogeneity and quality is obtained, which is reduced in threading screw dislocations, threading edge dislocations, basal plane dislocations, micropipes, and stacking faults.

A SiC single crystal is prepared by the solution process of placing a seed crystal in contact with a SiC solution in a crucible and letting a SiC single crystal to grow from the seed crystal. The method includes the first growth step of conducting crystal growth using (0001) or (000-1) plane of a SiC single crystal of which the seed crystal is composed, as the growth surface, and the second growth step of conducting crystal growth using (1-100) or (11-20) plane of a SiC single crystal resulting from the first growth step as the growth surface. A SiC single crystal of high homogeneity and quality is obtained, which is reduced in threading screw dislocations, threading edge dislocations, basal plane dislocations, micropipes, and stacking faults.

A silicon-based molten composition according to an exemplary embodiment of the present invention is used in a solution growing method for forming silicon carbide single crystal, and is expressed in Formula 1 including silicon (Si), chromium (Cr), vanadium (V), and aluminum (Al).

Si.sub.aCr.sub.bV.sub.cAl.sub.d [Formula 1]

In Formula 1, a is equal to or greater than 0.4 and equal to or less than 0.9, b+c is equal to or greater than 0.1 and equal to or less than 0.6, c/(b+c) is equal to or greater than 0.05 and equal to or less than 0.95, and d is equal to or greater than 0.01 and equal to or less than 0.1.