Phosphate nonlinear optical crystal as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of rare earth phosphate compounds, and particularly relates to a phosphate nonlinear optical crystal and a preparation method and application thereof. The invention provides a phosphate nonlinear optical crystal. The chemical formula of the phosphate nonlinear optical crystal is as shown in formula 1. The chemical formulas of the two crystals provided by the invention are respectively Y (PO3) 3 and Lu (PO3) 3, the molecular weights of the two crystals are respectively 325.82 and 411.88, and the two crystals are crystallized in a Cc space group of a monoclinic system. The invention provides the preparation method of the phosphate nonlinear optical crystal according to the technical scheme. The single crystals of the two phosphate nonlinear optical crystals provided by the invention are easy to grow, cut, grind, polish and preserve, are stable in air, are not easy to deliquesce and are insoluble in water; meanwhile, the optical performance is excellent, and the crystal can be applied to an all-solid-state laser as an ultraviolet-visible nonlinear optical crystal.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth phosphate compounds, and in particular relates to a phosphate nonlinear optical crystal and a preparation method and application thereof. Background Art

[0002] Functional materials constitute the material foundation of human survival and development, and they play a key role in all areas of our production and life. With the rapid progress of social economy, the demand for materials is growing, and at the same time, the requirements for their functionality and quality have become more stringent. Nonlinear optical (NLO) crystal materials are a branch of optoelectronic functional crystal materials. Nonlinear optical crystal materials are divided into natural growth and artificial growth. Ruby and quartz in nature are natural NLO crystal materials. For artificial nonlinear optical crystal materials, a number of commercialized crystal materials have been obtained through experimental growth in the past few decades, including β-BaB2O4 (β-BBO), LiB3O5 (LBO), KBe2BO3F2 (KBBF), KH2PO4 (KDP), KTiOPO4 (KTP), AgGaS2 (AGS), etc. These crystals are widely used in defense laser communications, medical detection equipment, solid-state lasers and other fields. The demand for linear / nonlinear optical crystals used in the visible light region has now been basically met, but the demand for linear / nonlinear optical crystals in the ultraviolet (wavelength below 400nm) and deep ultraviolet (below 200nm) bands is far from being met. The demand for ultraviolet / deep ultraviolet coherent light in emerging optoelectronic industries, such as semiconductor lithography, laser micromachining and modern scientific instruments is becoming increasingly urgent. Therefore, exploring new NLO crystals with short cutoff edges, wide phase matching ranges, large frequency response coefficients, moderate birefringence, good chemical and thermal stability, no deliquesce and easy processing is still a difficult problem in this field.

[0003] In recent years, many phosphate compounds with excellent performance have been synthesized, such as AM2(PO3)5(A=K,Rb,Cs;M=Ba), Ba3P3O 10 X(X=Cl,Br), RbNaMgP2O7, Na3Sc2(PO4)2F3, KLa(PO3)3, La(PO3)3, etc. Despite this, phosphate nonlinear optical crystal materials still have their own shortcomings, such as the frequency doubling effect and small birefringence are the most important problems facing phosphates. In order to obtain ultraviolet phosphate nonlinear optical crystal materials with suitable frequency doubling and birefringence, cations or π conjugated anion groups with stereochemically active lone pairs of electrons can be introduced into them, but d 0 The introduction of cations and cations containing lone pair electrons usually leads to a more serious band red shift.

[0004] In recent years, the introduction of rare earth elements into anion systems and the design and synthesis of rare earth crystals with novel structures and specific optical properties have attracted widespread attention. Rare earth elements have the following advantages: (1) The valence electron layer structure of rare earth atoms is complex, and its chemical activity is second only to alkali metals and alkaline earth metals; (2) They exist stably as +3 cations, and the radii of rare earth elements are similar, so new compounds can often be formed through cation regulation; (3) Rare earth cations can form larger coordinated polyhedra, which has a certain effect on optimizing optical anisotropy; (4) There are eight ions with closed-shell or near-closed-shell electronic configurations, namely Sc 3+ , Y 3+ ,La 3+ , Gd 3+ 、Ce 3+ (Ce 4+ )、Eu 3+ Yb 3+ 、Lu 3+ , this structure is conducive to the crystal's transmission of ultraviolet and deep ultraviolet light; (5) rare earth elements also have strong electronegativity. When coordinated with oxygen atoms, they can enhance the ionic properties of the target compound, thereby increasing the band gap. Therefore, the synthesis of rare earth phosphates is an effective means to design excellent nonlinear optical materials.

[0005] However, there is relatively little research on nonlinear optical crystals of rare earth phosphates in the existing technology, and single crystal growth is difficult. With the increasing demand for optoelectronic devices, new multifunctional crystal materials with comprehensive performance are needed, and it is urgent to design and synthesize new nonlinear optical materials. Summary of the invention

[0006] The purpose of the present invention is to provide a phosphate nonlinear optical crystal and a preparation method and application thereof. The two single crystals of phosphate nonlinear optical crystals provided by the present invention are easy to grow, cut, grind, polish and store, are stable in the air, are not easy to deliquesce and are insoluble in water; and have excellent optical properties, and can be used as ultraviolet-visible nonlinear optical crystals in all-solid-state lasers.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a phosphate nonlinear optical crystal, the chemical formula of the phosphate nonlinear optical crystal is shown in Formula 1:

[0009] A(PO3)3 formula 1;

[0010] In formula 1: A is Y or Lu;

[0011] The phosphate nonlinear optical crystal belongs to the monoclinic system and has a space group of Cc;

[0012] The molecular weight of yttrium phosphate nonlinear optical crystal is 325.82, and the unit cell parameters are β=127.581(2)°,Z=4,the unit cell volume is

[0013] The molecular weight of the lutetium phosphate nonlinear optical crystal is 411.88, and the unit cell parameters are β=127.3590(10)°,Z=12,the unit cell volume is

[0014]

[0015] The present invention provides a method for preparing the phosphate nonlinear optical crystal described in the above technical solution, comprising the following steps:

[0016] A mixed melt is prepared by using an A-containing compound, a P-containing compound and a flux;

[0017] first cooling the mixed melt to room temperature to obtain phosphate seed crystals;

[0018] The phosphate seed crystal is fixed on a seed crystal rod, and then the preheated seed crystal is lowered into the mixed melt for single crystal growth, so as to obtain an initial phosphate single crystal on the seed crystal rod;

[0019] The initial phosphate single crystal is cooled to room temperature for a second time to obtain a phosphate nonlinear optical crystal with a chemical formula as shown in Formula 1.

[0020] Preferably, the A-containing compound is a Y-containing compound or a Lu-containing compound; the purity of the Y-containing compound is ≥99.9%, and the Y-containing compound includes one or more of Y2O3, YF3, YCl3, YBr3, YI3 and Y2(CO3)3·3H2O; the purity of the Lu-containing compound is ≥99.9%, and the Lu-containing compound includes one or more of Lu2O3, LuF3, LuCl3, LuBr3 and Lu2(CO3)3·xH2O; the purity of the P-containing compound is ≥99.9%, and the P-containing compound includes one or more of NH4H2PO4, H3PO4 and P2O5; the purity of the flux is ≥99.9%, and the flux includes one or more of PbO, PbCl2, PbO-P2O5, PbCl2-P2O5 and PbO-PbCl2.

[0021] Preferably, the preparation method of the mixed melt comprises the following steps: mixing the A-containing compound and the P-containing compound according to the molar ratio of the A element and the P element in the chemical formula shown in Formula 1, and then calcining to obtain a phosphate polycrystalline product; the calcining temperature is 600 to 800° C., and the holding time is 36 to 48 hours;

[0022] The phosphate polycrystalline product and the flux are mixed and then smelted to obtain a mixed melt; the molar ratio of the phosphate polycrystalline product to the flux is 1:1-5; the smelting temperature is 650-920°C, the insulation time is 20-48h, and the heating rate from room temperature to the smelting temperature is 1-50°C / h.

[0023] Preferably, the preparation method of the mixed melt comprises the following steps: mixing an A-containing compound, a P-containing compound and a flux and then smelting them to obtain a mixed melt; the molar ratio of the A compound, the P-containing compound and the flux is 1:3-6:1-5; the smelting temperature is 650-920°C, the insulation time is 20-48h, and the heating rate from room temperature to the smelting temperature is 1-50°C / h.

[0024] Preferably, the first cooling temperature reduction rate is 0.5-10°C / h;

[0025] The conditions for the single crystal growth include: the mixed melt is kept warm and then cooled, and the seed crystal rod is rotated; the holding temperature of the mixed melt is 650-920° C., and the holding time is 15-80 min; the cooling rate is 0.1-3° C. / day; the rotation speed of the seed crystal rod is 1-60 rpm / min;

[0026] After the phosphate seed crystal is fixed on the seed crystal rod, before the preheated seed crystal is lowered into the mixed melt, the method further includes: preheating the phosphate seed crystal fixed on the seed crystal rod, wherein the preheating environment temperature is 650-920° C. and the time is 15-80 minutes;

[0027] The temperature reduction rate of the second cooling is 1 to 100° C. / h.

[0028] The present invention provides the use of the phosphate nonlinear optical crystal described in the above technical solution or the phosphate nonlinear optical crystal prepared by the preparation method described in the above technical solution as a nonlinear optical crystal.

[0029] Preferably, the phosphate nonlinear optical crystal is used as a deep ultraviolet nonlinear optical crystal.

[0030] Preferably, the phosphate nonlinear optical crystal is used in an all-solid-state laser.

[0031] The present invention provides the use of the phosphate nonlinear optical crystal described in the above technical scheme or the phosphate nonlinear optical crystal prepared by the preparation method described in the above technical scheme in nonlinear optical devices, and the nonlinear optical devices include frequency doubling generators, up or down frequency converters, optical parametric oscillators or laser frequency conversion devices.

[0032] The present invention provides a phosphate nonlinear optical crystal, the chemical formula of which is shown in Formula 1. The chemical formulas of the two crystals provided by the present invention are Y(PO3)3 and Lu(PO3)3, respectively, and the molecular weights are 325.82 and 411.88, respectively. Both crystals are crystallized in the Cc space group of the monoclinic system. The unit cell parameters are β=127.581(2)°,Z=4; β=127.3590(10)°,Z=12,the unit cell volumes are and The cutoff edges of both crystals are less than 200 nm, and the birefringence is between 0.018 (3000 nm) and 0.023 (1064 nm).

[0033] The present invention provides a method for preparing the phosphate nonlinear optical crystal described in the above technical solution. The present invention adopts a high-temperature melt method (self-melt spontaneous crystallization method, melt pulling method and melt top seed crystal method) and a flux method to grow crystals; it has the advantages of fast growth rate, low cost, and easy to obtain large-sized crystals. The crystal obtained by the preparation method of the present invention is easy to grow, easy to cut, easy to grind, easy to polish and easy to store, stable in the air, not easy to deliquesce, and insoluble in water; it can be used as a UV-visible nonlinear optical crystal in an all-solid-state laser.

[0034] The results of the examples show that the single crystal size of the two phosphate nonlinear optical crystals provided by the present invention is centimeter-level, transparent and without wrapping. According to the crystallographic data of the crystal, the crystal blank is oriented, the crystal is cut according to the required angle, thickness and cross-sectional size, and the light-transmitting surface of the crystal is polished, and it can be used as a nonlinear optical device. Both Y(PO3)3 and Lu(PO3)3 nonlinear optical crystals have the advantages of light transmission band reaching the ultraviolet region, stable physical and chemical properties, not easy to deliquesce, and easy to process and store. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The X-ray diffraction pattern of the single-phase polycrystalline powder prepared in the embodiment of the present invention is shown in FIG. Figure 1 (a) is the XRD spectrum of the single-phase polycrystalline powder of the Y(PO3)3 compound prepared in Example 1, and (b) is the XRD spectrum of the single-phase polycrystalline powder of the Lu(PO3)3 compound prepared in Example 16;

[0036] Figure 2 A working principle diagram of the nonlinear optical device provided by the present invention;

[0037] Figure 2In the middle: 1 is a laser, 2 is a fully focusing lens, 3 is a Y(PO3)3 or Lu(PO3)3 nonlinear optical crystal, 4 is a beam splitter, and 5 is a filter;

[0038] Figure 3 The crystal structures of Y(PO3)3 and Lu(PO3)3 crystals prepared in the embodiments of the present invention are shown in FIG. Figure 3 (a) is the crystal diagram of Y(PO3)3. Figure 3 (b) is the crystal diagram of Lu(PO3)3;

[0039] Figure 4 The thermogravimetric-differential thermal curve of the single-phase polycrystalline powder prepared in the embodiment of the present invention is shown in FIG. Figure 4 (a) is the thermogravimetric-differential thermal curve of the single-phase polycrystalline powder of Y(PO3)3 compound prepared in Example 1, Figure 4 (b) is the thermogravimetric-differential thermal curve of the single-phase polycrystalline powder of Lu(PO3)3 compound prepared in Example 16;

[0040] Figure 5 This is the infrared spectrum of the single-phase polycrystalline powder prepared in the embodiment of the present invention. Figure 5 (a) is the infrared spectrum of the single-phase polycrystalline powder of Y(PO3)3 compound prepared in Example 1, Figure 5 (b) is the infrared spectrum of the single-phase polycrystalline powder of Lu(PO3)3 compound prepared in Example 16;

[0041] Figure 6 This is the UV-visible diffuse reflectance spectrum of the single-phase polycrystalline powder prepared in the embodiment of the present invention. Figure 6 (a) is the UV-visible diffuse reflectance spectrum of the single-phase polycrystalline powder of the Y(PO3)3 compound prepared in Example 1, Figure 6 (b) is the UV-visible diffuse reflectance spectrum of the single-phase polycrystalline powder of Lu(PO3)3 compound prepared in Example 16. DETAILED DESCRIPTION

[0042] The present invention provides a phosphate nonlinear optical crystal, the chemical formula of the phosphate nonlinear optical crystal is shown in Formula 1:

[0043] A(PO3)3 formula 1;

[0044] In formula 1: A is Y or Lu;

[0045] The phosphate nonlinear optical crystal belongs to the monoclinic system and has a space group of Cc;

[0046] The molecular weight of yttrium phosphate nonlinear optical crystal is 325.82, and the unit cell parameters are β=127.581(2)°,Z=4,the unit cell volume is

[0047] The molecular weight of the lutetium phosphate nonlinear optical crystal is 411.88, and the unit cell parameters are β=127.3590(10)°,Z=12,the unit cell volume is

[0048]

[0049] The present invention provides a method for preparing the phosphate nonlinear optical crystal described in the above technical solution, comprising the following steps:

[0050] A mixed melt is prepared by using an A-containing compound, a P-containing compound and a flux;

[0051] first cooling the mixed melt to room temperature to obtain phosphate seed crystals;

[0052] The phosphate seed crystal is fixed on a seed crystal rod, and then the preheated seed crystal is lowered into the mixed melt for single crystal growth, so as to obtain an initial phosphate single crystal on the seed crystal rod;

[0053] The initial phosphate single crystal is cooled to room temperature for a second time to obtain a phosphate nonlinear optical crystal with a chemical formula as shown in Formula 1.

[0054] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0055] The present invention adopts A-containing compounds, P-containing compounds and flux to prepare a mixed melt. In the present invention, the A-containing compound is a Y-containing compound or a Lu-containing compound. The purity of the Y-containing compound is preferably ≥99.9%, and the Y-containing compound preferably includes one or more of Y2O3, YF3, YCl3, YBr3, YI3 and Y2(CO3)3·3H2O. The purity of the Lu-containing compound is preferably ≥99.9%, and the Lu-containing compound preferably includes one or more of Lu2O3, LuF3, LuCl3, LuBr3 and Lu2(CO3)3·xH2O. The purity of the P-containing compound is preferably ≥99.9%, and the P-containing compound preferably includes one or more of NH4H2PO4, H3PO4 and P2O5. The purity of the flux is preferably ≥99.9%, and the flux preferably includes one or more of PbO, PbCl2, PbO-P2O5 system, PbCl2-P2O5 system and PbO-PbCl2 system. The PbO-P2O5 system includes PbO and P2O5. The molar ratio of PbO to P2O5 in the PbO-P2O5 system is preferably 1 to 5:1. The PbCl2-P2O5 system includes PbCl2 and P2O5. The molar ratio of PbCl2 to P2O5 in the PbCl2-P2O5 system is preferably 1 to 5:1. The PbO-PbCl2 system includes PbO and PbCl2. The molar ratio of PbO to PbCl2 in the PbO-PbCl2 system is preferably 1 to 5:1.

[0056] In the present invention, the preparation method of the mixed melt preferably includes the following steps: mixing the A-containing compound and the P-containing compound according to the molar ratio of the A element and the P element in the chemical formula shown in Formula 1 and then roasting to obtain a phosphate polycrystalline product. In the present invention, the Y-containing compound and the P-containing compound are preferably mixed according to the molar ratio of the Y element and the P element of 1:3. The Lu-containing compound and the P-containing compound are preferably mixed according to the molar ratio of the Lu element and the P element of 1:3. In the present invention, the mixing obtains a mixed raw material, and before the roasting of the present invention, it is preferably further included: performing a first grinding of the mixed raw material to obtain a first grinding powder; pre-roasting the first grinding powder to obtain a pre-roasted material; and cooling the pre-roasted material to room temperature and then performing a second grinding to obtain a second grinding powder. The present invention preferably roasts the obtained second grinding powder. The present invention has no special requirements for the specific implementation of the first grinding and the second grinding. The temperature of the pre-roasting is preferably 300-350°C, and the holding time of the pre-roasting is preferably 24-36h. The present invention preferably loads the mixed raw material or the second ground powder into a crucible and places it in a muffle furnace for the roasting. The crucible is preferably an open corundum crucible or an open platinum crucible. The size of the crucible is preferably Φ60mm×60mm. The roasting temperature is preferably 600-800°C, and the holding time is preferably 36-48h. In a specific embodiment of the present invention, when the A-containing compound is a Y-containing compound, the roasting temperature is specifically 750°C. When the A-containing compound is a Lu-containing compound, the roasting temperature is specifically 650°C. The present invention preferably slowly cools the product obtained by the roasting to room temperature to obtain a phosphate polycrystalline product. The phosphate polycrystalline product is a Y(PO3)3 polycrystalline product or a Lu(PO3)3 polycrystalline product.

[0057] After obtaining the phosphate polycrystalline product, the present invention mixes the phosphate polycrystalline product and a flux and then smelts them to obtain a mixed melt. In the present invention, the molar ratio of the phosphate polycrystalline product to the flux is preferably 1:1 to 5, and specifically 1:5 or 1:1 in the embodiment. The present invention preferably puts the mixture obtained by mixing the phosphate polycrystalline product and the flux into a platinum crucible, and then places it in a single crystal growth furnace for smelting. The smelting temperature is preferably 650 to 920°C, and specifically 650°C, 920°C, 750°C, 870°C, 770°C, 800°C, 780°C, 700°C, 790°C, 680°C, 830°C, 840°C, 880°C, 850°C or 900°C in the embodiment. The holding time of the smelting is preferably 20 to 48 hours, and in the embodiments, it is specifically 20 hours, 24 hours, 30 hours, 48 ​​hours, 22 hours, 46 hours, 34 hours, 36 hours, 48 ​​hours, 25 hours, 29 hours, 44 hours, 26 hours, 43 hours, 42 hours, 32 hours or 28 hours. The heating rate from room temperature to the smelting temperature is preferably 1 to 50°C / h, and in the embodiments, it is specifically 2°C / h, 50°C / h, 3°C / h, 10°C / h, 8°C / h, 25°C / h, 0.5°C / h, 5°C / h, 20°C / h, 1°C / h, 15°C / h, 33°C / h, 28°C / h, 34°C / h, 43°C / h, 45°C / h, 23°C / h, 38°C / h, 44°C / h, 17°C / h, 29°C / h or 12°C / h.

[0058] Alternatively, the preparation method of the mixed melt preferably comprises the following steps: mixing the A-containing compound, the P-containing compound and the flux and then smelting them to obtain a mixed melt. In the present invention, the molar ratio of the A compound, the P-containing compound and the flux is preferably 1:3 to 6:1 to 5, and in the embodiment, it is specifically 1:5:1, 1:1:1, 1:2:1, 1:3:1 or 1:4:1. In the present invention, the mixture obtained by mixing the A-containing compound, the P-containing compound and the flux is preferably charged into a platinum crucible, and then placed in a single crystal growth furnace for smelting. The smelting temperature is preferably 650 to 920°C, and in the embodiment, it is specifically 650°C, 920°C, 750°C, 870°C, 770°C, 800°C, 780°C, 700°C, 790°C, 680°C, 830°C, 840°C, 880°C, 850°C or 900°C. The holding time of the smelting is preferably 20 to 48 hours, and in the embodiments, it is specifically 20 hours, 24 hours, 30 hours, 48 ​​hours, 22 hours, 46 hours, 34 hours, 36 hours, 48 ​​hours, 25 hours, 29 hours, 44 hours, 26 hours, 43 hours, 42 hours, 32 hours or 28 hours. The heating rate from room temperature to the smelting temperature is preferably 1 to 50°C / h, and in the embodiments, it is specifically 2°C / h, 50°C / h, 3°C / h, 10°C / h, 8°C / h, 25°C / h, 0.5°C / h, 5°C / h, 20°C / h, 1°C / h, 15°C / h, 33°C / h, 28°C / h, 34°C / h, 43°C / h, 45°C / h, 23°C / h, 38°C / h, 44°C / h, 17°C / h, 29°C / h or 12°C / h.

[0059] After obtaining the mixed melt, the present invention first cools the mixed melt to room temperature to obtain phosphate seed crystals. In the present invention, the temperature of the mixed melt during the first cooling is preferably 650-920°C, specifically 650°C, 920°C, 750°C, 870°C, 770°C, 800°C, 780°C, 700°C, 790°C, 680°C, 830°C, 840°C, 880°C, 850°C or 900°C. The cooling rate of the first cooling is preferably 0.5-10°C / h, and in the embodiments, it is specifically 1°C / h, 0.5°C / h, 2°C / h, 5°C / h, 1.8°C / h, 10°C / h, 7°C / h, 6°C / h, 1.6°C / h, 7.8°C / h, 6.8°C / h, 7.5°C / h, 0.8°C / h, 0.5°C / h, 3.5°C / h, 3.2°C / h, 9°C / h, 4.7°C / h, 1.5°C / h, 2.8°C / h, 4.5°C / h or 6.5°C / h. The phosphate seed crystals are obtained by spontaneous crystallization of the mixed melt.

[0060] After obtaining the phosphate seed crystal, the present invention fixes the phosphate seed crystal on a seed crystal rod, and then lowers the preheated seed crystal into the mixed melt for single crystal growth, and obtains an initial phosphate single crystal on the seed crystal rod. In the present invention, the phosphate seed crystal is fixed on the seed crystal rod in any direction. In the present invention, the mixed melt is located in a platinum crucible in the single crystal growth furnace, and the present invention preferably lowers the phosphate seed crystal fixed on the seed crystal rod from the top of the single crystal growth furnace. After the phosphate seed crystal is fixed on the seed crystal rod and before the preheated seed crystal is lowered into the mixed melt, the present invention preferably also includes: preheating the phosphate seed crystal fixed on the seed crystal rod. The preheating is carried out in a single crystal growth furnace, the preheating environment temperature is preferably 650-920°C, the time is preferably 15-80 min, and specifically 60 min, 55 min, 48 min, 80 min, 30 min, 15 min, 34 min, 25 min, 75 min, 24 min, 20 min, 42 min, 54 min, 36 min or 72 min in the embodiment. After the preheating is completed, a preheated seed crystal is obtained. The present invention preferably places the preheated seed crystal into the mixed melt for single crystal growth. The conditions for single crystal growth preferably include: the mixed melt is kept warm and then cooled, and the seed crystal rod rotates. The holding temperature of the mixed melt is preferably 650-920°C, and the holding time is preferably 15-80 min, specifically 60 min, 80 min, 30 min, 50 min, 30 min, 18 min, 15 min, 76 min, 55 min, 19 min, 21 min, 45 min, 25 min, 50 min, 65 min, 75 min, 60 min, 48 min or 72 min in the embodiments; during the holding process, the phosphate seed crystals are melted back in the mixed melt.The cooling rate is preferably 0.1-3°C / day, and in the embodiments, it is specifically 0.1°C / day, 1°C / day, 0.2°C / day, 0.8°C / day, 3°C / day, 0.7°C / day, 2.2°C / day, 1.8°C / day, 1.9°C / day, 2.3°C / day, 0.3°C / day, 0.9°C / day, 0.5°C / day, 2.5°C / day, 2.2°C / day, 2.8°C / day or 1.2°C / day; the rotation speed of the seed rod is preferably 1-60rpm / min, and in the embodiments, it is specifically 1rpm / min, 12rpm / min. n, 25rpm / min, 54rpm / min, 55rpm / min, 47rpm / min, 37rpm / min, 57rpm / min, 18rpm / min, 12rpm / min, 37rpm / min, 22r pm / min, 34rpm / min, 60rpm / min, 32rpm / min, 17rpm / min, 15rpm / min, 8rpm / min, 45rpm / min, 55rpm / min or 48rpm / min.

[0061] In the present invention, after the initial phosphate single crystal grows to a desired size, the present invention lifts the initial phosphate single crystal off the surface of the mixed melt.

[0062] After obtaining the initial phosphate single crystal, the present invention performs a second cooling of the initial phosphate single crystal to room temperature to obtain a phosphate nonlinear optical crystal having a chemical formula as shown in Formula 1. In the present invention, the cooling rate of the second cooling is preferably 1 to 100°C / h, and in the embodiment, it is specifically 1°C / h, 20°C / h, 30°C / h, 10°C / h, 50°C / h, 70°C / h, 100°C / h, 87°C / h, 67°C / h, 4°C / h, 44°C / h, 15°C / h, 40°C / h, 60°C / h, 100°C / h or 75°C / h. The second cooling is preferably performed in a single crystal growth furnace. After obtaining the phosphate nonlinear optical crystal having a chemical formula as shown in Formula 1, the present invention takes out the obtained phosphate nonlinear optical crystal having a chemical formula as shown in Formula 1 from the furnace of the single crystal growth furnace, that is, an yttrium phosphate nonlinear optical crystal or a lutetium phosphate nonlinear optical crystal is obtained.

[0063] The present invention provides the use of the phosphate nonlinear optical crystal described in the above technical solution or the phosphate nonlinear optical crystal prepared by the preparation method described in the above technical solution as a nonlinear optical crystal.

[0064] In the present invention, the phosphate nonlinear optical crystal is used as a deep ultraviolet nonlinear optical crystal.

[0065] In the present invention, the phosphate nonlinear optical crystal is used in an all-solid-state laser.

[0066] The present invention provides the use of the phosphate nonlinear optical crystal described in the above technical solution or the phosphate nonlinear optical crystal prepared by the preparation method described in the above technical solution in a nonlinear optical device. In the present invention, the nonlinear optical device includes a frequency doubling generator, an up or down frequency converter, an optical parametric oscillator or a laser frequency conversion device.

[0067] In a specific embodiment of the present invention, the yttrium phosphate nonlinear optical crystal has a molecular formula of Y(PO3)3, and is prepared by a solid phase reaction method according to the following chemical reaction formula:

[0068] (1)Y2O3+6NH4H2PO4→2Y(PO3)3+6NH3↑+9H2O↑

[0069] (2)Y2(CO3)3·3H2O+6NH4H2PO4→2Y(PO3)3+3CO2↑+6NH3↑+12H2O↑

[0070] (3)YF3+3NH4H2PO4→Y(PO3)3+3NH3↑+3H2O↑+3HF↑

[0071] (4)YCl3+3NH4H2PO4→Y(PO3)3+3NH3↑+3H2O↑+3HCl↑

[0072] (5)YBr3+3NH4H2PO4→Y(PO3)3+3NH3↑+3H2O↑+3HBr↑

[0073] (6)YI3+3NH4H2PO4→Y(PO3)3+3NH3↑+3H2O↑+3HI↑

[0074] (7)Y2O3+3P2O5→2Y(PO3)3

[0075] (8)Y2(CO3)3·3H2O+3P2O5→2Y(PO3)3+3CO2↑+3H2O↑

[0076] (9)Y2O3+6H3PO4→2Y(PO3)3+9H2O↑

[0077] (10)Y2(CO3)3·3H2O+6H3PO4→2Y(PO3)3+3CO2↑+12H2O↑

[0078] (11)YF3+3H3PO4→Y(PO3)3+3HF↑+3H2O↑

[0079] (12)YCl3+3H3PO4→Y(PO3)3+3H2O↑+3HCl↑

[0080] (13)YBr3+3H3PO4→Y(PO3)3+3H2O↑+3HBr↑

[0081] (14)YI3+3H3PO4→Y(PO3)3+3H2O↑+3HI↑

[0082] In a specific embodiment of the present invention, the lutetium phosphate nonlinear optical crystal has a molecular formula of Lu(PO3)3, and is prepared by a solid phase reaction method according to the following chemical reaction formula:

[0083] (1)Lu2O3+6NH4H2PO4→2Lu(PO3)3+6NH3↑+9H2O↑

[0084] (2)Lu2(CO3)3·xH2O+6NH4H2PO4→2Lu(PO3)3+3CO2↑+6NH3↑+(9+x)H2O↑

[0085] (3)LuF3+3NH4H2PO4→Lu(PO3)3+3NH3↑+3H2O↑+3HF↑

[0086] (4)LuCl3+3NH4H2PO4→Lu(PO3)3+3NH3↑+3H2O↑+3HCl↑

[0087] (5)LuBr3+3NH4H2PO4→Lu(PO3)3+3NH3↑+3H2O↑+3HBr↑

[0088] (6)Lu2O3+3P2O5→2Lu(PO3)3

[0089] (7)Lu2(CO3)3·xH2O+3P2O5→2Lu(PO3)3+3CO2↑+(3+x)H2O↑

[0090] (8)Lu2O3+6H3PO4→2Lu(PO3)3+9H2O↑

[0091] (9)Lu2(CO3)3·xH2O+6H3PO4→2Lu(PO3)3+3CO2↑+(9+x)H2O↑

[0092] (10)LuF3+3H3PO4→Lu(PO3)3+3HF↑+3H2O↑

[0093] (11)LuCl3+3H3PO4→Lu(PO3)3+3H2O↑+3HCl↑

[0094] (12)LuBr3+3H3PO4→Lu(PO3)3+3H2O↑+3HBr↑

[0095] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0096] The following Examples 1 to 14 use a solid phase reaction method to prepare yttrium phosphate single crystals with a chemical formula of Y(PO3)3.

[0097] The following Examples 16 to 27 use a solid phase reaction method to prepare lutetium phosphate single crystals with a chemical formula of Lu(PO3)3.

[0098] Example 1

[0099] According to the chemical reaction formula Y2O3+6NH4H2PO4→2Y(PO3)3+6NH3↑+9H2O↑, Y(PO3)3 nonlinear optical crystal was prepared:

[0100] a. Mix Y2O3 and NH4H2PO4 in a molar ratio of 1:6 in an agate mortar and grind them carefully to make them fully mixed. Then put them into a Φ60mm×60mm open corundum crucible, put them into a muffle furnace, slowly heat them to 350℃, keep the temperature constant for 24h, cool them to room temperature, take them out and grind them for the second time, transfer them to an open corundum crucible, put them into a muffle furnace, heat them to 750℃, keep the temperature constant for 48h, slowly cool them to room temperature, take them out and grind them to obtain a single-phase polycrystalline powder of yttrium phosphate compound, and then perform X-ray analysis on the product. Figure 1 As shown in (a) in the figure, the obtained X-ray spectrum is consistent with the X-ray spectrum obtained from the yttrium phosphate single crystal structure.

[0101] b. The polycrystalline powder obtained in step a is mixed evenly with flux PbO at a molar ratio of 1:5, and heated to 920° C. at a heating rate of 50° C. / h, and kept at the constant temperature for 20 hours to obtain a mixed melt;

[0102] c. Preparation of seed crystals: After cooling the mixed melt obtained in step b, transfer it to a single crystal growth furnace, raise the temperature to 920°C until the melt is uniform and transparent, and slowly cool it to room temperature at a rate of 1°C / h to obtain Y(PO3)3 seed crystals by spontaneous crystallization;

[0103] d. Growing crystals: Fix the seed crystals obtained in step c on the seed crystal rod. The seed crystals can be fixed on the seed crystal rod in any direction. Lower the seed crystals from the top of the crystal growth furnace. Preheat the seed crystals for 60 minutes. Lower the seed crystals into a mixed melt of Y(PO3)3 and flux heated to 920°C for remelting. Keep the temperature constant for 60 minutes. Slowly cool the temperature at a rate of 0.1°C / day. Rotate the seed crystal rod at a speed of 1 rpm / min to grow the crystal. After the single crystal grows to the desired size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 1°C / h. Then take the crystal out of the furnace to obtain a Y(PO3)3 nonlinear optical crystal.

[0104] Example 2

[0105] According to the chemical reaction formula Y2(CO3)3·3H2O+6NH4H2PO4→2Y(PO3)3+3CO2↑+6NH3↑+12H2O↑, Y(PO3)3 nonlinear optical crystal was prepared:

[0106] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0107] The Y(PO3)3 polycrystalline powder and flux PbO were mixed uniformly in a molar ratio of 1:1 and loaded into a platinum crucible, and heated to 750°C at a heating rate of 2°C / h and kept at this temperature for 24h to obtain a mixed melt;

[0108] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 750°C until the melt is uniform and transparent, then cool it to room temperature at a rate of 0.5°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0109] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 55 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux heated to 750℃ for remelting. Keep the temperature constant for 80 minutes. Slowly cool at a rate of 1℃ / day. Rotate the seed crystal rod at 12rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 20℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0110] Example 3

[0111] According to the chemical reaction formula YF3+3NH4H2PO4→Y(PO3)3+3NH3↑+3H2O↑+3HF↑, Y(PO3)3 nonlinear optical crystal is prepared:

[0112] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0113] The Y(PO3)3 polycrystalline powder and flux PbCl2 were mixed uniformly in a molar ratio of 1:1 and loaded into a platinum crucible, and heated to 870°C in a muffle furnace at a heating rate of 3°C / h and kept at a constant temperature for 30h to obtain a mixed melt;

[0114] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 870°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 1°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0115] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 60 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux heated to 870℃ for remelting. Keep the temperature constant for 30 minutes. Slowly cool at a rate of 0.2℃ / day. Rotate the seed crystal rod at 25rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 30℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0116] Example 4

[0117] According to the chemical reaction formula YCl3+3NH4H2PO4→Y(PO3)3+3NH3↑+3H2O↑+3HCl↑, Y(PO3)3 nonlinear optical crystal was prepared:

[0118] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0119] The Y(PO3)3 polycrystalline powder and flux PbO-PbCl2 were mixed uniformly in a molar ratio of 1:5:1 and loaded into a platinum crucible, and heated to 650°C in a muffle furnace at a heating rate of 5°C / h and kept at a constant temperature for 36 hours to obtain a mixed melt;

[0120] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 650°C until the melt is uniform and transparent, then cool it to room temperature at a rate of 2°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0121] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 48 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux heated to 650℃ for remelting. Keep the temperature constant for 50 minutes. Slowly cool at a rate of 0.8℃ / day. Rotate the seed crystal rod at 25rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 10℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0122] Example 5

[0123] According to the chemical reaction formula YBr3+3NH4H2PO4→Y(PO3)3+3NH3↑+3H2O↑+3HBr↑, prepare Y(PO3)3 nonlinear optical crystal:

[0124] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0125] The Y(PO3)3 polycrystalline powder and flux PbCl2 were mixed uniformly in a molar ratio of 1:5 and loaded into a platinum crucible, and heated to 770°C in a muffle furnace at a heating rate of 10°C / h and kept at a constant temperature for 48h to obtain a mixed melt;

[0126] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 770°C until the melt is uniform and transparent, then cool it to room temperature at a rate of 5°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0127] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 80 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux heated to 770℃ for remelting. Keep the temperature constant for 30 minutes. Slowly cool at a rate of 3℃ / day. Rotate the seed crystal rod at 54rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 50℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0128] Example 6

[0129] According to the chemical reaction formula YI3+3NH4H2PO4→Y(PO3)3+3NH3↑+3H2O↑+3HI↑, Y(PO3)3 nonlinear optical crystal was prepared:

[0130] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0131] The Y(PO3)3 polycrystalline powder and flux PbO-PbCl2 were mixed uniformly in a molar ratio of 1:1:1 and loaded into a platinum crucible. The mixture was heated to 880°C in a muffle furnace at a rate of 20°C / h and kept at the constant temperature for 48h to obtain a mixed melt.

[0132] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 880°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 1.8°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0133] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 30 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux at 880℃ for remelting. Keep the temperature constant for 30 minutes. Slowly cool at a rate of 0.7℃ / day. Rotate the seed crystal rod at 55rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 70℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0134] Example 7

[0135] According to the chemical reaction formula Y2O3+3P2O5→2Y(PO3)3, Y(PO3)3 nonlinear optical crystal is prepared:

[0136] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0137] The Y(PO3)3 polycrystalline powder and flux PbO-P2O5 were mixed uniformly in a molar ratio of 1:5:1 and loaded into a platinum crucible, and heated to 880°C in a muffle furnace at a heating rate of 30°C / h and kept at the constant temperature for 30h to obtain a mixed melt;

[0138] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 770°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 10°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0139] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace, preheat the seed crystal for 80 minutes, lower the seed crystal into the mixed melt of Y(PO3)3 and flux at 880℃ for remelting, keep the temperature constant for 50 minutes, slowly cool at a rate of 2.2℃ / day, rotate the seed crystal rod at 47rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface, cool it to room temperature at a rate of 100℃ / h, and then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0140] Example 8

[0141] According to the chemical reaction formula Y2(CO3)3·3H2O+3P2O5→2Y(PO3)3+3CO2↑+3H2O↑, Y(PO3)3 nonlinear optical crystal is prepared:

[0142] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0143] The Y(PO3)3 polycrystalline powder and flux PbCl2-P2O5 were mixed uniformly in a molar ratio of 1:1:1 and loaded into a platinum crucible, and heated to 780°C in a muffle furnace at a heating rate of 1°C / h and kept at this temperature for 25h to obtain a mixed melt;

[0144] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 780°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 7°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0145] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 15 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux heated to 780℃ for remelting. Keep the temperature constant for 18 minutes. Slowly cool at a rate of 1.8℃ / day. Rotate the seed crystal rod at 37rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 100℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0146] Example 9

[0147] According to the chemical reaction formula Y2O3+6H3PO4→2Y(PO3)3+9H2O↑, Y(PO3)3 nonlinear optical crystal is prepared:

[0148] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0149] The Y(PO3)3 polycrystalline powder and flux PbCl2-P2O5 were mixed uniformly in a molar ratio of 1:5:1 and loaded into a platinum crucible, and heated to 800°C in a muffle furnace at a heating rate of 15°C / h and kept at the constant temperature for 29h to obtain a mixed melt;

[0150] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 800°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 6°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0151] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 15 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux heated to 800℃ for remelting. Keep the temperature constant for 15 minutes. Slowly cool at a rate of 1.8℃ / day. Rotate the seed crystal rod at 57rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 87℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0152] Example 10

[0153] According to the chemical reaction formula Y2(CO3)3·3H2O+6H3PO4→2Y(PO3)3+3CO2↑+12H2O↑, the Y(PO3)3 nonlinear optical crystal was prepared:

[0154] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0155] The Y(PO3)3 polycrystalline powder and flux PbO-P2O5 were mixed uniformly in a molar ratio of 1:1:1 and loaded into a platinum crucible, and heated to 700°C in a muffle furnace at a heating rate of 33°C / h and kept at a constant temperature for 44h to obtain a mixed melt;

[0156] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 700°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 1.6°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0157] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 34 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux heated to 700℃ for remelting. Keep the temperature constant for 15 minutes. Slowly cool at a rate of 1.9℃ / day. Rotate the seed crystal rod at 54rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 1℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0158] Embodiment 11

[0159] According to the chemical reaction formula YF3+3H3PO4→Y(PO3)3+3HF↑+3H2O↑, Y(PO3)3 nonlinear optical crystal is prepared:

[0160] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0161] The Y(PO3)3 polycrystalline powder and flux PbO-PbCl2 were mixed uniformly in a molar ratio of 1:2:1 and loaded into a platinum crucible, and heated to 790°C in a muffle furnace at a heating rate of 28°C / h and kept at the constant temperature for 26h to obtain a mixed melt;

[0162] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 790°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 7.8°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0163] Growing crystal: fix the seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 25 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux heated to 790℃ for remelting. Keep the temperature constant for 76 minutes. Slowly cool at a rate of 2.3℃ / day. Rotate the seed crystal rod at 18rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 67℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0164] Example 12

[0165] According to the chemical reaction formula YCl3+3H3PO4→Y(PO3)3+3H2O↑+3HCl↑, Y(PO3)3 nonlinear optical crystal is prepared:

[0166] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0167] The Y(PO3)3 polycrystalline powder and flux PbO-P2O5 were mixed uniformly in a molar ratio of 1:3:1 and loaded into a platinum crucible, and heated to 680°C in a muffle furnace at a heating rate of 34°C / h and kept at the constant temperature for 43h to obtain a mixed melt;

[0168] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 680°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 6.8°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0169] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 75 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux heated to 680℃ for remelting. Keep the temperature constant for 55 minutes. Slowly cool at a rate of 3℃ / day. Rotate the seed crystal rod at 12rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 4℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0170] Embodiment 13

[0171] According to the chemical reaction formula YBr3+3H3PO4→Y(PO3)3+3H2O↑+3HBr↑, Y(PO3)3 nonlinear optical crystal is prepared:

[0172] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0173] The Y(PO3)3 polycrystalline powder and flux PbCl2-P2O5 were mixed uniformly in a molar ratio of 1:4:1 and loaded into a platinum crucible, and heated to 830°C in a muffle furnace at a heating rate of 43°C / h and kept at the constant temperature for 36h to obtain a mixed melt;

[0174] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 830°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 7.5°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0175] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 24 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux heated to 830℃ for remelting. Keep the temperature constant for 19 minutes. Slowly cool at a rate of 0.9℃ / day. Rotate the seed crystal rod at 37rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 44℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0176] Embodiment 14

[0177] According to the chemical reaction formula YI3+3H3PO4→Y(PO3)3+3H2O↑+3HI↑, Y(PO3)3 nonlinear optical crystal is prepared:

[0178] The single-phase polycrystalline powder of Y(PO3)3 compound was prepared according to step a in Example 1:

[0179] The Y(PO3)3 polycrystalline powder and flux PbO-PbCl2 were mixed uniformly in a molar ratio of 1:4:1 and loaded into a platinum crucible, and heated to 840°C in a muffle furnace at a heating rate of 45°C / h and kept at a constant temperature for 42h to obtain a mixed melt;

[0180] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 840°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 0.8°C / h, and spontaneously crystallize to obtain Y(PO3)3 seed crystals;

[0181] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 34 minutes. Lower the seed crystal into the mixed melt of Y(PO3)3 and flux heated to 840℃ for remelting. Keep the temperature constant for 21 minutes. Slowly cool at a rate of 2.3℃ / day. Rotate the seed crystal rod at 1rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 1℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0182] Embodiment 15

[0183] Any Y(PO3)3 crystal obtained in Examples 1 to 14 is processed in a matching direction, and the attached Figure 2 As shown in the figure, it is placed at position 3, at room temperature, using the 1064nm output of a Q-switched Nd:YAG laser as the light source, and a weaker 532nm doubled frequency green light output is observed.

[0184] Example 16

[0185] According to the chemical reaction formula Lu2O3+6NH4H2PO4→2Lu(PO3)3+6NH3↑+9H2O↑, Lu(PO3)3 nonlinear optical crystal was prepared:

[0186] a. Mix Lu2O3 and NH4H2PO4 in a molar ratio of 1:6 in an agate mortar and grind them carefully to make them fully mixed. Then put them into a Φ60mm×60mm open corundum crucible, put them into a muffle furnace, slowly heat them to 350℃, keep the temperature constant for 24h, cool them to room temperature, take them out and grind them for the second time, transfer them to an open corundum crucible, put them into a muffle furnace, heat them to 650℃, keep the temperature constant for 48h, slowly cool them to room temperature, take them out and grind them to obtain a single-phase polycrystalline powder of lutetium phosphate compound, and then perform X-ray analysis on the product. Figure 1 As shown in (b), the obtained X-ray spectrum is consistent with the X-ray spectrum obtained from the lutetium phosphate single crystal structure.

[0187] b. The polycrystalline powder obtained in step a was mixed evenly with flux PbO at a molar ratio of 1:5, and heated to 920° C. at a heating rate of 23° C. / h, and kept at the constant temperature for 32 hours to obtain a mixed melt;

[0188] c. Preparation of seed crystals: After cooling the mixed melt obtained in step b, transfer it to a single crystal growth furnace, raise the temperature to 920°C until the melt is uniform and transparent, and slowly cool it to room temperature at a rate of 0.5°C / h to obtain Lu(PO3)3 seed crystals by spontaneous crystallization;

[0189] d. Growing crystals: Fix the seed crystals obtained in step c on the seed crystal rod. The seed crystals can be fixed on the seed crystal rod in any direction. Lower the seed crystals from the top of the crystal growth furnace. Preheat the seed crystals for 20 minutes. Lower the seed crystals into a mixed melt of Lu(PO3)3 and flux heated to 920°C for remelting. Keep the temperature constant for 15 minutes. Slowly cool the temperature at a rate of 0.5°C / day. Rotate the seed crystal rod at a speed of 12 rpm / min to grow the crystal. After the single crystal grows to the desired size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 15°C / h. Then take the crystal out of the furnace to obtain the Lu(PO3)3 nonlinear optical crystal.

[0190] Embodiment 17

[0191] According to the chemical reaction formula Lu2(CO3)3·xH2O+6NH4H2PO4→2Lu(PO3)3+3CO2↑+6NH3↑+(9+x)H2O↑, Lu(PO3)3 nonlinear optical crystal was prepared:

[0192] The single-phase polycrystalline powder of Lu(PO3)3 compound was prepared according to step a in Example 16:

[0193] The Lu(PO3)3 polycrystalline powder and flux PbCl2 were mixed uniformly in a molar ratio of 1:1 and loaded into a platinum crucible, and heated to 800°C at a heating rate of 50°C / h and kept at this temperature for 22h to obtain a mixed melt;

[0194] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 800°C until the melt is uniform and transparent, then cool it to room temperature at a rate of 3.5°C / h, and spontaneously crystallize to obtain Lu(PO3)3 seed crystals;

[0195] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 60 minutes. Lower the seed crystal into the mixed melt of Lu(PO3)3 and flux heated to 800℃ for remelting. Keep the temperature constant for 45 minutes. Slowly cool at a rate of 0.1℃ / day. Rotate the seed crystal rod at 22rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 20℃ / h. Then take the crystal out of the furnace to obtain Lu(PO3)3 nonlinear optical crystal.

[0196] Embodiment 18

[0197] According to the chemical reaction formula LuF3+3NH4H2PO4→Lu(PO3)3+3NH3↑+3H2O↑+3HF↑, Lu(PO3)3 nonlinear optical crystal was prepared:

[0198] The single-phase polycrystalline powder of Lu(PO3)3 compound was prepared according to step a in Example 16:

[0199] The Lu(PO3)3 polycrystalline powder and flux PbO-P2O5 were mixed uniformly in a molar ratio of 1:5:1 and loaded into a platinum crucible, and heated to 880°C in a muffle furnace at a heating rate of 45°C / h and kept at a constant temperature for 48h to obtain a mixed melt;

[0200] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 880°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 3.2°C / h, and spontaneously crystallize to obtain Lu(PO3)3 seed crystals;

[0201] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 80 minutes. Lower the seed crystal into the mixed melt of Lu(PO3)3 and flux heated to 880℃ for remelting. Keep the temperature constant for 80 minutes. Slowly cool at a rate of 3℃ / day. Rotate the seed crystal rod at 34rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 1℃ / h. Then take the crystal out of the furnace to obtain Lu(PO3)3 nonlinear optical crystal.

[0202] Embodiment 19

[0203] According to the chemical reaction formula LuCl3+3NH4H2PO4→Lu(PO3)3+3NH3↑+3H2O↑+3HCl↑, Lu(PO3)3 nonlinear optical crystal was prepared:

[0204] The single-phase polycrystalline powder of Lu(PO3)3 compound was prepared according to step a in Example 16:

[0205] The Lu(PO3)3 polycrystalline powder and flux PbO-PbCl2 were mixed uniformly in a molar ratio of 1:5:1 and loaded into a platinum crucible, and heated to 650°C in a muffle furnace at a heating rate of 1°C / h and kept at a constant temperature for 20h to obtain a mixed melt;

[0206] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 650°C until the melt is uniform and transparent, then cool it to room temperature at a rate of 10°C / h, and spontaneously crystallize to obtain Lu(PO3)3 seed crystals;

[0207] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 42 minutes. Lower the seed crystal into the mixed melt of Lu(PO3)3 and flux heated to 650℃ for remelting. Keep the temperature constant for 30 minutes. Slowly cool at a rate of 2.5℃ / day. Rotate the seed crystal rod at 60rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 40℃ / h. Then take the crystal out of the furnace to obtain Lu(PO3)3 nonlinear optical crystal.

[0208] Embodiment 20

[0209] According to the chemical reaction formula LuBr3+3NH4H2PO4→Lu(PO3)3+3NH3↑+3H2O↑+3HBr↑, Lu(PO3)3 nonlinear optical crystal is prepared:

[0210] The single-phase polycrystalline powder of Lu(PO3)3 compound was prepared according to step a in Example 16:

[0211] The Lu(PO3)3 polycrystalline powder and flux PbO were mixed uniformly in a molar ratio of 1:1 and loaded into a platinum crucible, and heated to 780°C in a muffle furnace at a heating rate of 8°C / h and kept at a constant temperature for 46 hours to obtain a mixed melt;

[0212] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 780°C until the melt is uniform and transparent, then cool it to room temperature at a rate of 0.8°C / h, and spontaneously crystallize to obtain Lu(PO3)3 seed crystals;

[0213] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 15 minutes. Lower the seed crystal into the mixed melt of Lu(PO3)3 and flux heated to 780℃ for remelting. Keep the temperature constant for 25 minutes. Slowly cool at a rate of 3℃ / day. Rotate the seed crystal rod at 32rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 60℃ / h. Then take the crystal out of the furnace to obtain Y(PO3)3 nonlinear optical crystal.

[0214] Embodiment 21

[0215] According to the chemical reaction formula Lu2O3+3P2O5→2Lu(PO3)3, Lu(PO3)3 nonlinear optical crystal is prepared:

[0216] The single-phase polycrystalline powder of Lu(PO3)3 compound was prepared according to step a in Example 16:

[0217] The Lu(PO3)3 polycrystalline powder and flux PbO-P2O5 were mixed uniformly in a molar ratio of 1:1:1 and loaded into a platinum crucible. The mixture was heated to 900°C at a rate of 38°C / h in a muffle furnace and kept at a constant temperature for 36h to obtain a mixed melt.

[0218] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 900°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 9°C / h, and spontaneously crystallize to obtain Lu(PO3)3 seed crystals;

[0219] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 34 minutes. Lower the seed crystal into the mixed melt of Lu(PO3)3 and flux heated to 900℃ for remelting. Keep the temperature constant for 50 minutes. Slowly cool at a rate of 1℃ / day. Rotate the seed crystal rod at 17rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 100℃ / h. Then take the crystal out of the furnace to obtain Lu(PO3)3 nonlinear optical crystal.

[0220] Embodiment 22

[0221] According to the chemical reaction formula Lu2(CO3)3·xH2O+3P2O5→2Lu(PO3)3+3CO2↑+(3+x)H2O↑, Lu(PO3)3 nonlinear optical crystal is prepared:

[0222] The single-phase polycrystalline powder of Lu(PO3)3 compound was prepared according to step a in Example 16:

[0223] The Lu(PO3)3 polycrystalline powder and flux PbO-PbCl2 were mixed uniformly in a molar ratio of 1:1:1 and loaded into a platinum crucible, and heated to 750°C in a muffle furnace at a heating rate of 44°C / h and kept at a constant temperature for 28h to obtain a mixed melt;

[0224] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 750°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 4.7°C / h, and spontaneously crystallize to obtain Lu(PO3)3 seed crystals;

[0225] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 48 minutes. Lower the seed crystal into the mixed melt of Lu(PO3)3 and flux heated to 750℃ for remelting. Keep the temperature constant for 65 minutes. Slowly cool at a rate of 0.3℃ / day. Rotate the seed crystal rod at 17rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 80℃ / h. Then take the crystal out of the furnace to obtain Lu(PO3)3 nonlinear optical crystal.

[0226] Embodiment 23

[0227] According to the chemical reaction formula Lu2O3+6H3PO4→2Lu(PO3)3+9H2O↑, Lu(PO3)3 nonlinear optical crystal was prepared:

[0228] The single-phase polycrystalline powder of Lu(PO3)3 compound was prepared according to step a in Example 16:

[0229] The Lu(PO3)3 polycrystalline powder and flux PbCl2-P2O5 were mixed uniformly in a molar ratio of 1:5:1 and loaded into a platinum crucible, and heated to 850°C in a muffle furnace at a heating rate of 17°C / h and kept at a constant temperature for 30 hours to obtain a mixed melt;

[0230] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, heat it to 850°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 1.5°C / h to spontaneously crystallize and obtain Lu(PO3)3 seed crystals;

[0231] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 54 minutes. Lower the seed crystal into the mixed melt of Lu(PO3)3 and flux heated to 850℃ for remelting. Keep the temperature constant for 75 minutes. Slowly cool at a rate of 0.8℃ / day. Rotate the seed crystal rod at 15rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 25℃ / h. Then take the crystal out of the furnace to obtain Lu(PO3)3 nonlinear optical crystal.

[0232] Embodiment 24

[0233] (13) According to the chemical reaction formula Lu2(CO3)3·xH2O+6H3PO4→2Lu(PO3)3+3CO2↑+(9+x)H2O↑, Lu(PO3)3 nonlinear optical crystal is prepared:

[0234] The single-phase polycrystalline powder of Lu(PO3)3 compound was prepared according to step a in Example 16:

[0235] The Lu(PO3)3 polycrystalline powder and flux PbCl2 were mixed uniformly in a molar ratio of 1:5 and loaded into a platinum crucible, and heated to 700°C in a muffle furnace at a heating rate of 25°C / h and kept at the constant temperature for 24h to obtain a mixed melt;

[0236] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, heat it to 700°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 2.8°C / h to spontaneously crystallize and obtain Lu(PO3)3 seed crystals;

[0237] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 36 minutes. Lower the seed crystal into the mixed melt of Lu(PO3)3 and flux heated to 700℃ for remelting. Keep the temperature constant for 60 minutes. Slowly cool at a rate of 1.8℃ / day. Rotate the seed crystal rod at 8rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 8℃ / h. Then take the crystal out of the furnace to obtain Lu(PO3)3 nonlinear optical crystal.

[0238] Embodiment 25

[0239] According to the chemical reaction formula LuF3+3H3PO4→Lu(PO3)3+3HF↑+3H2O↑, Lu(PO3)3 nonlinear optical crystal was prepared:

[0240] The single-phase polycrystalline powder of Lu(PO3)3 compound was prepared according to step a in Example 16:

[0241] The Lu(PO3)3 polycrystalline powder and flux PbCl2-P2O5 were mixed uniformly in a molar ratio of 1:1:1 and loaded into a platinum crucible, and heated to 780°C in a muffle furnace at a heating rate of 29°C / h and kept at the constant temperature for 44h to obtain a mixed melt;

[0242] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 780°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 4.5°C / h, and spontaneously crystallize to obtain Lu(PO3)3 seed crystals;

[0243] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 55 minutes. Lower the seed crystal into the mixed melt of Lu(PO3)3 and flux heated to 780℃ for remelting. Keep the temperature constant for 48 minutes. Slowly cool at a rate of 2.2℃ / day. Rotate the seed crystal rod at 45rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 10℃ / h. Then take the crystal out of the furnace to obtain Lu(PO3)3 nonlinear optical crystal.

[0244] Embodiment 26

[0245] According to the chemical reaction formula LuCl3+3H3PO4→Lu(PO3)3+3H2O↑+3HCl↑, Lu(PO3)3 nonlinear optical crystal was prepared:

[0246] The single-phase polycrystalline powder of Lu(PO3)3 compound was prepared according to step a in Example 16:

[0247] The Lu(PO3)3 polycrystalline powder and flux PbO-PbCl2 were mixed uniformly in a molar ratio of 1:3:1 and loaded into a platinum crucible, and heated to 680°C in a muffle furnace at a heating rate of 12°C / h and kept at a constant temperature for 32h to obtain a mixed melt;

[0248] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, raise the temperature to 680°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 6.5°C / h, and spontaneously crystallize to obtain Lu(PO3)3 seed crystals;

[0249] Growing crystal: fix the seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 72 minutes. Lower the seed crystal into the mixed melt of Lu(PO3)3 and flux heated to 680℃ for remelting. Keep the temperature constant for 72 minutes. Slowly cool at a rate of 2.8℃ / day. Rotate the seed crystal rod at 55rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 70℃ / h. Then take the crystal out of the furnace to obtain Lu(PO3)3 nonlinear optical crystal.

[0250] Embodiment 27

[0251] According to the chemical reaction formula LuBr3+3H3PO4→Lu(PO3)3+3H2O↑+3HBr↑, Lu(PO3)3 nonlinear optical crystal was prepared:

[0252] The single-phase polycrystalline powder of Lu(PO3)3 compound was prepared according to step a in Example 16:

[0253] The Lu(PO3)3 polycrystalline powder and flux PbCl2 were mixed uniformly in a molar ratio of 1:2 and loaded into a platinum crucible, and heated to 800°C in a muffle furnace at a heating rate of 5°C / h and kept at a constant temperature for 34h to obtain a mixed melt;

[0254] Preparation of seed crystals: After cooling the obtained mixed melt, transfer it to a single crystal growth furnace, heat it to 800°C until the melt is uniform and transparent, then slowly cool it to room temperature at a rate of 0.8°C / h, and spontaneously crystallize to obtain Lu(PO3)3 seed crystals;

[0255] Growing crystal: fix the obtained seed crystal on the seed crystal rod. The seed crystal can be fixed on the seed crystal rod in any direction. Lower the seed crystal from the top of the crystal growth furnace. Preheat the seed crystal for 45 minutes. Lower the seed crystal into the mixed melt of Lu(PO3)3 and flux heated to 800℃ for remelting. Keep the temperature constant for 18 minutes. Slowly cool at a rate of 1.2℃ / day. Rotate the seed crystal rod at 48rpm / min to grow the crystal. After the single crystal grows to the required size, lift the crystal from the liquid surface and cool it to room temperature at a rate of 75℃ / h. Then take the crystal out of the furnace to obtain Lu(PO3)3 nonlinear optical crystal.

[0256] Embodiment 28

[0257] Any Lu(PO3)3 crystal obtained in Examples 16 to 27 is processed in a matching direction, and the attached Figure 2 As shown in the figure, it is placed at position 3, at room temperature, using the 1064nm output of a Q-switched Nd:YAG laser as the light source, and a weaker 532nm doubled frequency green light output is observed.

[0258] It can be seen from the above embodiments that the preparation method provided by the present invention can obtain Y(PO3)3 and Lu(PO3)3 nonlinear optical crystals with a size of centimeter level. By using a large-sized crucible and extending the growth period of the crystal, correspondingly large-sized nonlinear optical crystals Y(PO3)3 and Lu(PO3)3 can be obtained. Y(PO3)3 and Lu(PO3)3 nonlinear optical crystals are easy to grow, transparent and without wrapping, and have the advantages of fast growth rate, low cost, and easy to obtain large-sized crystals.

[0259] Figure 4 The thermogravimetric-differential thermal curve of the single-phase polycrystalline powder prepared in the embodiment of the present invention is shown in FIG. Figure 4 (a) is the thermogravimetric-differential thermal curve of the single-phase polycrystalline powder of Y(PO3)3 compound prepared in Example 1, Figure 4 (b) is the thermogravimetric-differential thermal curve of the single-phase polycrystalline powder of Lu(PO3)3 compound prepared in Example 16. Figure 4 It can be concluded that the single-phase polycrystalline powder of Y(PO3)3 compound and the single-phase polycrystalline powder of Lu(PO3)3 compound prepared in the embodiment of the present invention have no obvious weight loss phenomenon in the process of slowly rising from room temperature to 1000°C, and no obvious endothermic peak or exothermic peak appears on the DTA curve. It is preliminarily confirmed that these two nonlinear optical crystals have good thermal stability.

[0260] Figure 5 This is the infrared spectrum of the single-phase polycrystalline powder prepared in the embodiment of the present invention. Figure 5 (a) is the infrared spectrum of the single-phase polycrystalline powder of Y(PO3)3 compound prepared in Example 1, Figure 5(b) is the infrared spectrum of the single-phase polycrystalline powder of Lu(PO3)3 compound prepared in Example 16. Figure 5 It is used to confirm the characteristic vibration mode of the anionic group of the P atom. The conclusion information is as follows: in the range of 3500 to 1600 cm -1 No OH was found in the range - Vibration bands related to H2O. A(PO3)3 (A=Y or Lu) at 1257 and 1255 cm -1 and 1097, 1106 and 1030cm -1 The absorption peaks of 772, 749, 711 and 709 cm are the characteristic peaks of PO stretching vibration. -1 The absorption peaks at 512 cm are the characteristic peaks of symmetric and asymmetric stretching vibrations of POP, while the absorption peaks at 512 cm -1 and 484-546cm -1 The absorption peak is mainly the fundamental vibration characteristic peak of the PO4 group. Infrared spectroscopy further confirmed that [PO3] ∞ The presence of groups.

[0261] Figure 6 This is the UV-visible diffuse reflectance spectrum of the single-phase polycrystalline powder prepared in the embodiment of the present invention. Figure 6 (a) is the UV-visible diffuse reflectance spectrum of the single-phase polycrystalline powder of the Y(PO3)3 compound prepared in Example 1, Figure 6 (b) is the UV-visible diffuse reflectance spectrum of the single-phase polycrystalline powder of Lu(PO3)3 compound prepared in Example 16. Figure 6 Used to confirm the characteristic vibration mode of the anionic group of the P atom, the conclusion information is as follows:

[0262] The UV absorption cutoff edge of these two materials is less than 200nm, and the reflectivity is 50%-60%. According to the Kubelka-Munk function (R represents reflectivity), the band gap values ​​of Y(PO3)3 and Lu(PO3)3 are both greater than 6.2eV. The results show that the above two crystals are deep ultraviolet optical crystals.

[0263] By adopting the preparation method and use of yttrium phosphate and lutetium phosphate nonlinear optical crystals described in the present invention, large-sized Y(PO3)3 and Lu(PO3)3 nonlinear optical crystals are obtained. According to the crystallographic data of the crystal, the crystal blank is oriented, the crystal is cut according to the required angle, thickness and cross-sectional size, and the light-transmitting surface of the crystal is polished, and then it can be used as a nonlinear optical device. Both Y(PO3)3 and Lu(PO3)3 nonlinear optical crystals have the advantages of a light transmission band reaching the ultraviolet region, stable physical and chemical properties, not easy to deliquesce, easy to process and preserve, etc.

[0264] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A phosphate nonlinear optical crystal, characterized in that: The chemical formula of the phosphate nonlinear optical crystal is shown in Formula 1: A(PO3)3 formula 1; In formula 1: A is Y or Lu; The phosphate nonlinear optical crystal belongs to the monoclinic system and has a space group of Cc; The molecular weight of yttrium phosphate nonlinear optical crystal is 325.82, and the unit cell parameters are β=127.581(2)°,Z=4,the unit cell volume is The molecular weight of the lutetium phosphate nonlinear optical crystal is 411.88, and the unit cell parameters are β=127.3590(10)°,Z=12,the unit cell volume is 2. The method for preparing the phosphate nonlinear optical crystal according to claim 1, characterized in that: The following steps are involved: A mixed melt is prepared by using an A-containing compound, a P-containing compound and a flux; first cooling the mixed melt to room temperature to obtain phosphate seed crystals; The phosphate seed crystal is fixed on a seed crystal rod, and then the preheated seed crystal is lowered into the mixed melt for single crystal growth, so as to obtain an initial phosphate single crystal on the seed crystal rod; The initial phosphate single crystal is cooled to room temperature for a second time to obtain a phosphate nonlinear optical crystal with a chemical formula as shown in Formula 1.

3. The preparation method according to claim 2, characterized in that: The A-containing compound is a Y-containing compound or a Lu-containing compound; the purity of the Y-containing compound is ≥99.9%, and the Y-containing compound includes one or more of Y2O3, YF3, YCl3, YBr3, YI3 and Y2(CO3)3·3H2O; the purity of the Lu-containing compound is ≥99.9%, and the Lu-containing compound includes one or more of Lu2O3, LuF3, LuCl3, LuBr3 and Lu2(CO3)3·xH2O; the purity of the P-containing compound is ≥99.9%, and the P-containing compound includes one or more of NH4H2PO4, H3PO4 and P2O5; the purity of the flux is ≥99.9%, and the flux includes one or more of PbO, PbCl2, PbO-P2O5, PbCl2-P2O5 and PbO-PbCl2.

4. The preparation method according to claim 2 or 3, characterized in that: The preparation method of the mixed melt comprises the following steps: mixing an A-containing compound and a P-containing compound according to the molar ratio of the A element and the P element in the chemical formula shown in Formula 1, and then calcining to obtain a phosphate polycrystalline product; the calcining temperature is 600-800° C., and the heat preservation time is 36-48 hours; The phosphate polycrystalline product and the flux are mixed and then smelted to obtain a mixed melt; the molar ratio of the phosphate polycrystalline product to the flux is 1:1-5; the smelting temperature is 650-920°C, the insulation time is 20-48h, and the heating rate from room temperature to the smelting temperature is 1-50°C / h.

5. The preparation method according to claim 2 or 3, characterized in that: The preparation method of the mixed melt comprises the following steps: mixing an A-containing compound, a P-containing compound and a flux and then smelting them to obtain a mixed melt; the molar ratio of the A compound, the P-containing compound and the flux is 1:3-6:1-5; the smelting temperature is 650-920°C, the insulation time is 20-48h, and the heating rate from room temperature to the smelting temperature is 1-50°C / h.

6. The preparation method according to claim 2, characterized in that: The first cooling temperature reduction rate is 0.5-10°C / h; The conditions for the single crystal growth include: the mixed melt is kept warm and then cooled, and the seed crystal rod is rotated; the holding temperature of the mixed melt is 650-920° C., and the holding time is 15-80 min; the cooling rate is 0.1-3° C. / day; the rotation speed of the seed crystal rod is 1-60 rpm / min; After the phosphate seed crystal is fixed on the seed crystal rod, before the preheated seed crystal is lowered into the mixed melt, the method further includes: preheating the phosphate seed crystal fixed on the seed crystal rod, wherein the preheating environment temperature is 650-920° C. and the time is 15-80 minutes; The temperature reduction rate of the second cooling is 1 to 100° C. / h.

7. Use of the phosphate nonlinear optical crystal according to claim 1 or the phosphate nonlinear optical crystal prepared by the preparation method according to any one of claims 2 to 6 as a nonlinear optical crystal.

8. The use according to claim 7, characterized in that: The phosphate nonlinear optical crystal is used as a deep ultraviolet nonlinear optical crystal.

9. The use according to claim 8, characterized in that: Application of the phosphate nonlinear optical crystal in all-solid-state laser.

10. Use of the phosphate nonlinear optical crystal according to claim 1 or the phosphate nonlinear optical crystal prepared by the preparation method according to any one of claims 2 to 6 in a nonlinear optical device, characterized in that: The nonlinear optical device includes a frequency doubling generator, an up or down frequency converter, an optical parametric oscillator or a laser frequency conversion device.

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