A method for growing a crystalline composition, the first crystalline composition may include gallium and nitrogen. The crystalline composition may have an infrared absorption peak at about 3175 cm.sup.−1, with an absorbance per unit thickness of greater than about 0.01 cm.sup.−1. In one embodiment, the composition ay have an amount of oxygen present in a concentration of less than about 3×10.sup.18 per cubic centimeter, and may be free of two-dimensional planar boundary defects in a determined volume of the first crystalline composition.

A method for growing a crystalline composition, the first crystalline composition may include gallium and nitrogen. The crystalline composition may have an infrared absorption peak at about 3175 cm.sup.−1, with an absorbance per unit thickness of greater than about 0.01 cm.sup.−1. In one embodiment, the composition ay have an amount of oxygen present in a concentration of less than about 3×10.sup.18 per cubic centimeter, and may be free of two-dimensional planar boundary defects in a determined volume of the first crystalline composition.

The application discloses a preparation method of monocrystal uranium dioxide nuclear fuel pellets, comprising: granulating and pelleting UO.sub.2 powder to obtain UO.sub.2 pellets; then coating surfaces of the UO.sub.2 pellets with monocrystal growth additive micro powder to form core-shell structure particles; and activated-sintering the core-shell structure particles at high temperature, liquefying the monocrystal growth additive on the surface of the core-shell structure particle at high temperature and then diffusing into UO.sub.2 pellets, dissolving the UO.sub.3 in the liquid monocrystal growth additive, and recrystallizing the UO.sub.2 to form the monocrystal UO.sub.2 nuclear fuel pellets.

The application discloses a preparation method of monocrystal uranium dioxide nuclear fuel pellets, comprising: granulating and pelleting UO.sub.2 powder to obtain UO.sub.2 pellets; then coating surfaces of the UO.sub.2 pellets with monocrystal growth additive micro powder to form core-shell structure particles; and activated-sintering the core-shell structure particles at high temperature, liquefying the monocrystal growth additive on the surface of the core-shell structure particle at high temperature and then diffusing into UO.sub.2 pellets, dissolving the UO.sub.3 in the liquid monocrystal growth additive, and recrystallizing the UO.sub.2 to form the monocrystal UO.sub.2 nuclear fuel pellets.

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 method for growing a crystalline composition, the first crystalline composition may include gallium and nitrogen. The crystalline composition may have an infrared absorption peak at about 3175 cm.sup.1, with an absorbance per unit thickness of greater than about 0.01 cm.sup.1. In one embodiment, the composition ay have an amount of oxygen present in a concentration of less than about 310.sup.18 per cubic centimeter, and may be free of two-dimensional planar boundary defects in a determined volume of the first crystalline composition.

A method for growing a crystalline composition, the first crystalline composition may include gallium and nitrogen. The crystalline composition may have an infrared absorption peak at about 3175 cm.sup.1, with an absorbance per unit thickness of greater than about 0.01 cm.sup.1. In one embodiment, the composition ay have an amount of oxygen present in a concentration of less than about 310.sup.18 per cubic centimeter, and may be free of two-dimensional planar boundary defects in a determined volume of the first crystalline composition.

The application discloses a preparation method of monocrystal uranium dioxide nuclear fuel pellets, comprising: granulating and pelleting UO.sub.2 powder to obtain UO.sub.2 pellets; then coating surfaces of the UO.sub.2 pellets with monocrystal growth additive micro powder to form core-shell structure particles; and activated-sintering the core-shell structure particles at high temperature, liquefying the monocrystal growth additive on the surface of the core-shell structure particle at high temperature and then diffusing into UO.sub.2 pellets, dissolving the UO.sub.3 in the liquid monocrystal growth additive, and recrystallizing the UO.sub.2 to form the monocrystal UO.sub.2 nuclear fuel pellets.

The application discloses a preparation method of monocrystal uranium dioxide nuclear fuel pellets, comprising: granulating and pelleting UO.sub.2 powder to obtain UO.sub.2 pellets; then coating surfaces of the UO.sub.2 pellets with monocrystal growth additive micro powder to form core-shell structure particles; and activated-sintering the core-shell structure particles at high temperature, liquefying the monocrystal growth additive on the surface of the core-shell structure particle at high temperature and then diffusing into UO.sub.2 pellets, dissolving the UO.sub.3 in the liquid monocrystal growth additive, and recrystallizing the UO.sub.2 to form the monocrystal UO.sub.2 nuclear fuel pellets.