A nonlinear optical crystal of barium cesium borate, a preparation method and use thereof are provided. The nonlinear optical crystal has a chemical formula of CsBa.sub.3B.sub.11O.sub.20 and a molecular weight of 983.84. The nonlinear optical crystal belongs to an orthorhombic crystal system; a space group of the nonlinear optical crystal is Cmc2.sub.1; lattice parameters of the nonlinear optical crystal are a=19.011(7) ?, b=10.837(4) ?, c=8.578(3) ?, Z=4, V=1767.4(11) ?.sup.3; and a Mohs hardness of the nonlinear optical crystal is 4-5. The nonlinear optical crystal is grown by a flux method. The nonlinear optical crystal of the barium cesium borate obtained is used for a manufacture of non-linear optical devices. The nonlinear optical crystal has a large size of centimeter-scale at least and is prepared by fast, simple and low-cost operations. The nonlinear optical crystal prepared has a large size, a wide light transmission band and good mechanical properties.

The present application discloses a nonlinear optical crystal material, preparation method and application of the nonlinear optical crystal material. A nonlinear optical crystal material, whose molecular formula is Ga.sub.2Se.sub.3; wherein the crystal structure of said nonlinear optical crystal material belongs to trigonal system, space group R3 with the lattice parameters of a=b=34.2 , c=910 , ==90, =120 and Z=1. The nonlinear optical crystal material has an excellent infrared nonlinear optical performance, whose frequency-doubling intensity can reach 9.3 times of AgGaS.sub.2 with the same particle size, and it meets type-I phase matching; and its laser damage threshold can reach 7.5 times of AgGaS.sub.2 with the same particle size. The nonlinear optical crystal material has important application value in the frequency-converters which can be used for frequency doubling, sum frequency, difference frequency, optical parametric oscillation of laser in mid and far infrared waveband, and the like.

A thermal insulation panel is consist of an impermeable barrier and backing, a surface of low emissivity, an adhesive, a mixture of phononic cocrystals at both sides, and a support material in a honeycomb structure in between two sides. The panel reduces heat transfer and has an overall thermal conductivity in order of 10.sup.3 w/(m.Math.K), and a density of 20-100 kg/m.sup.3. The panel can be cut to any sizes to meet requirements for installation, and can be stacked or piled up to meet the requirements of thickness and thermal resistance in application.

A thermal insulation panel is consist of an impermeable barrier and backing, a surface of low emissivity, an adhesive, a mixture of phononic cocrystals at both sides, and a support material in a honeycomb structure in between two sides. The panel reduces heat transfer and has an overall thermal conductivity in order of 10.sup.3 w/(m.Math.K), and a density of 20-100 kg/m.sup.3. The panel can be cut to any sizes to meet requirements for installation, and can be stacked or piled up to meet the requirements of thickness and thermal resistance in application.

It is used a crucible containing a flux and a source material, a reaction vessel containing the crucible, an intermediate vessel containing the reaction vessel, and a pressure vessel containing the intermediate vessel and used to fill a gas comprising at least a nitrogen atom. When the flux and the source material are melted by heating to grow the nitride crystal, a vapor of an organic compound is provided in a space outside of the reaction vessel and inside of the intermediate vessel.

It is used a crucible containing a flux and a source material, a reaction vessel containing the crucible, an intermediate vessel containing the reaction vessel, and a pressure vessel containing the intermediate vessel and used to fill a gas comprising at least a nitrogen atom. When the flux and the source material are melted by heating to grow the nitride crystal, a vapor of an organic compound is provided in a space outside of the reaction vessel and inside of the intermediate vessel.

A composite substrate includes a polycrystalline ceramic substrate, a silicon substrate directly bonded to the polycrystalline ceramic substrate, a seed crystal film formed on the silicon substrate by vapor phase process and made of a nitride of a group 13 element, and a gallium nitride crystal layer grown on the seed crystal film by flux method.

A composite substrate includes a polycrystalline ceramic substrate, a silicon substrate directly bonded to the polycrystalline ceramic substrate, a seed crystal film formed on the silicon substrate by vapor phase process and made of a nitride of a group 13 element, and a gallium nitride crystal layer grown on the seed crystal film by flux method.

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 the field of nonlinear optical crystal materials and provided herein a Li.sub.4Sr(BO.sub.3).sub.2 compound, a Li.sub.4Sr(BO.sub.3).sub.2 nonlinear optical crystal as well as preparation method and use thereof. The Li.sub.4Sr(BO.sub.3).sub.2 nonlinear optical crystal has a second harmonic conversion efficiency at 1064 nm of about two times that of a KH.sub.2PO.sub.4 (KDP) crystal, and an UV absorption cut-off edge less than 190 nm. Furthermore, the crystal did not disintegrate. By flux method with Li.sub.2O, Li.sub.2OB.sub.2O and Li.sub.2OB.sub.2O.sub.3LiF used as flux agent, large-size and transparent Li.sub.4Sr(BO.sub.3).sub.2 nonlinear optical crystal can grow. The Li.sub.4Sr(BO.sub.3).sub.2 crystal had stable physicochemical properties, moderate hardness, and was easy to cut, processing, preserve and use. Therefore it can be used for preparing nonlinear optical devices and thus for developing nonlinear optical applications in the ultraviolet and deep-ultraviolet band.