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.

The present invention relates to a method for producing a silicon ingot from a silicon melt by directional solidification, wherein the growth of the silicon ingot is initiated by bringing the silicon melt into contact with at least one silicon seed, characterised in that at least the surface of the seed brought into contact with the silicon melt is oxidised.

The present invention relates to a method for producing a silicon ingot from a silicon melt by directional solidification, wherein the growth of the silicon ingot is initiated by bringing the silicon melt into contact with at least one silicon seed, characterised in that at least the surface of the seed brought into contact with the silicon melt is oxidised.

A method for growing a -Ga.sub.2O.sub.3-based single crystal, can provide a plate-shaped -Ga.sub.2O.sub.3-based single crystal having high crystal quality. In one embodiment, a method for growing a -Ga.sub.2O.sub.3-based single crystal employing an EFG method is provided, the method including: bringing a plate-shaped seed crystal into contact with a Ga.sub.2O.sub.3-based melt, wherein the plate-shaped seed crystal includes a -Ga.sub.2O.sub.3-based single crystal having a defect density of not more than 510.sup.5 /cm.sup.2 in the whole region; and pulling up the seed crystal to grow a -Ga.sub.2O.sub.3-based single crystal.

A method for growing a -Ga.sub.2O.sub.3-based single crystal, can provide a plate-shaped -Ga.sub.2O.sub.3-based single crystal having high crystal quality. In one embodiment, a method for growing a -Ga.sub.2O.sub.3-based single crystal employing an EFG method is provided, the method including: bringing a plate-shaped seed crystal into contact with a Ga.sub.2O.sub.3-based melt, wherein the plate-shaped seed crystal includes a -Ga.sub.2O.sub.3-based single crystal having a defect density of not more than 510.sup.5 /cm.sup.2 in the whole region; and pulling up the seed crystal to grow a -Ga.sub.2O.sub.3-based single crystal.

Provided is one embodiment which is a method for growing a -Ga.sub.2O.sub.3-based single crystal including contacting a flat plate-shaped seed crystal with a Ga.sub.2O.sub.3-based melt, and pulling up the seed crystal such that a flat plate-shaped -Ga.sub.2O.sub.3-based single crystal having a principal surface which intersects a surface is grown without inheriting a crystal information of a vaporized material of the Ga.sub.2O.sub.3-based melt adhered to the principal surface of the seed crystal, wherein when growing the -Ga.sub.2O.sub.3-based single crystal, a shoulder of the -Ga.sub.2O.sub.3-based single crystal is widened in a thickness direction (t) thereof.

Provided is one embodiment which is a method for growing a -Ga.sub.2O.sub.3-based single crystal including contacting a flat plate-shaped seed crystal with a Ga.sub.2O.sub.3-based melt, and pulling up the seed crystal such that a flat plate-shaped -Ga.sub.2O.sub.3-based single crystal having a principal surface which intersects a surface is grown without inheriting a crystal information of a vaporized material of the Ga.sub.2O.sub.3-based melt adhered to the principal surface of the seed crystal, wherein when growing the -Ga.sub.2O.sub.3-based single crystal, a shoulder of the -Ga.sub.2O.sub.3-based single crystal is widened in a thickness direction (t) thereof.

Provided is one embodiment which is a method for growing a -Ga.sub.2O.sub.3-based single crystal which uses the EFG method and includes raising a Ga.sub.2O.sub.3 melt inside a crucible up to a die opening via a die slit such that a seed crystal is contacted with the Ga.sub.2O.sub.3-based melt in the opening of the die with a horizontal position of the seed crystal shifted in a width direction (W) from a center in the width direction (W) of the die, and pulling up the seed crystal contacting the Ga.sub.2O.sub.3-based melt so as to grown a -Ga.sub.2O.sub.3 single crystal.

Provided is one embodiment which is a method for growing a -Ga.sub.2O.sub.3-based single crystal which uses the EFG method and includes raising a Ga.sub.2O.sub.3 melt inside a crucible up to a die opening via a die slit such that a seed crystal is contacted with the Ga.sub.2O.sub.3-based melt in the opening of the die with a horizontal position of the seed crystal shifted in a width direction (W) from a center in the width direction (W) of the die, and pulling up the seed crystal contacting the Ga.sub.2O.sub.3-based melt so as to grown a -Ga.sub.2O.sub.3 single crystal.