Alkali metal composite molybdate compound, alkali metal composite molybdate nonlinear optical crystal and preparation method and application of alkali metal composite molybdate nonlinear optical crystal

Abstract

The invention relates to an alkali metal composite molybdate compound, an alkali metal composite molybdate nonlinear optical crystal and a preparation method and application of the alkali metal composite molybdate compound and the alkali metal composite molybdate nonlinear optical crystal, the chemical general formulas of the compound and the crystal are KAMo2O7, A is Rb or Cs, the crystal belongs to an orthorhombic system, the space group is Ama2, and the cell parameter # imgabs0 # # imgabs1 # Z is 4. The alkali metal composite molybdate compound is synthesized by adopting a solid-phase reaction method, the nonlinear optical crystal grows by adopting a high-temperature melt method or an aqueous solution method, and the nonlinear optical crystal can be used for manufacturing a second harmonic generator, an upper frequency converter, a lower frequency converter, an optical parametric oscillator and the like.

Description

Technical Field

[0001] The present invention relates to an alkali metal composite molybdate compound and an alkali metal composite molybdate nonlinear optical crystal and a preparation method and application thereof, and in particular to an application of the nonlinear optical crystal in a nonlinear optical device. Background Art

[0002] Exploring new nonlinear optical crystals with large frequency doubling effect, wide transmission band, large optical damage threshold and stable physical and chemical properties has always been a hot topic in the field of laser frequency conversion. The main nonlinear optical materials currently include: β-BaB2O4 (BBO) crystal, LiB3O5 (LBO) crystal, CsB3O5 (CBO) crystal, CsLiB6O 10 (CLBO) crystals and KBe2BO3F2 (KBBF) crystals. Although the crystal growth technology for these materials has matured, significant shortcomings remain, such as easy deliquesce, long growth cycles, severe layered growth habits, and high costs. Therefore, the search for new nonlinear optical crystal materials remains a crucial and arduous task. To address these shortcomings in nonlinear optical crystals, scientists around the world are actively exploring and researching various new types of nonlinear optical crystals, focusing not only on the optical and mechanical properties of the crystals but also, increasingly, on the crystal preparation characteristics.

[0003] Molybdates have very interesting structural chemistry and applications in optical materials, such as laser crystal materials, luminescent matrix materials, laser frequency doubling materials, birefringence materials, and ultraviolet-transmitting materials. Therefore, the synthesis of new molybdate structures is of great research significance for the structural chemistry of molybdate compounds and the development of molybdate optical materials. The introduction of alkali metal complexes (K, Cs) or alkaline earth metals can effectively increase the band gap of the compound. 0 Transition metals (Mo 6+ ) exhibits a second-order Jahn-Teller (SOJT) effect, playing an important role in the design and synthesis of NLO compounds and possessing significant application value. Therefore, the synthesis of molybdates will be an effective means of designing excellent nonlinear optical materials. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes an alkali metal composite molybdate compound and an alkali metal composite molybdate nonlinear optical crystal, as well as a preparation method and use thereof.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] One of the objects of the present invention is to provide an alkali metal complex molybdate compound.

[0007] A second object of the present invention is to provide a method for preparing the alkali metal composite molybdate compound.

[0008] A third object of the present invention is to provide an alkali metal composite molybdate nonlinear optical crystal.

[0009] A fourth object of the present invention is to provide a method for preparing the alkali metal composite molybdate nonlinear optical crystal.

[0010] A fifth object of the present invention is to provide an application of the alkali metal composite molybdate nonlinear optical crystal.

[0011] One of the purposes of the present invention is achieved in that:

[0012] The present invention aims to provide an alkali metal composite molybdate compound, the chemical formula of which is KAMo2O7 (A=Rb, Cs), the molecular formulas of which are KRbMo2O7 and KCsMo2O7, and the molecular weights of which are 428.47 and 475.89, respectively.

[0013] The second object of the present invention is achieved in this way:

[0014] The alkali metal composite molybdate compound is prepared by a solid phase reaction method according to the following chemical reaction formula:

[0015] 1)K2CO3+A2CO3(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+2CO2↑

[0016] 2)2KNO3+A2CO3(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+2NO2↑+CO2↑+0.5O2↑

[0017] 3)2KOH+A2CO3(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+H2O↑+CO2↑

[0018] 5)K2CO3+2AOH(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+H2O↑+CO2↑

[0019] 6)2KNO3+2AOH(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+H2O↑+2NO2↑+0.5O2↑

[0020] 7)KOH+AOH(A=Rb,Cs)+2MoO3→KAMo2O7(A=Rb,Cs)+H2O↑

[0021] 8)K2CO3+2ANO3(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+2NO2↑+CO2↑+0.5O2↑

[0022] 9)2KNO3+2ANO3(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+4NO2↑+O2↑

[0023] 10)2KOH+2ANO3(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+2NO2↑+H2O↑+0.5O2↑

[0024] 11)K2C2O4+A2CO3(A=Rb,Cs)+4MoO3+0.5O2→2KAMo2O7(A=Rb,Cs)+3CO2↑

[0025] 12)K2C2O4+2AOH(A=Rb,Cs)+4MoO3+0.5O2→2KAMo2O7(A=Rb,Cs)+H2O↑+2CO2↑

[0026] 13)K2C2O4+2ANO3(A=Rb,Cs)+4MoO3+O2→2KAMo2O7(A=Rb,Cs)+2CO2↑+2NO2↑

[0027] 14)K2MoO4+A2CO3(A=Rb,Cs)+3MoO3→2KAMo2O7(A=Rb,Cs)+CO2↑

[0028] 15)K2MoO4+2AOH(A=Rb,Cs)+3MoO3→2KAMo2O7(A=Rb,Cs)+H2O↑

[0029] 16)K2MoO4+2ANO3(A=Rb,Cs)+3MoO3→2KAMo2O7(A=Rb,Cs)+2NO2↑+0.5O2↑

[0030] 17)K2MoO4+A2MoO4(A=Rb,Cs)+2MoO3→2KAMo2O7(A=Rb,Cs)

[0031] 18)2KCl+A2CO3(A=Rb,Cs)+4MoO3+0.5O2→2KAMo2O7(A=Rb,Cs)+CO2↑+Cl2↑

[0032] 19)K2CO3+A2CO3(A=Rb,Cs)+4H2MoO4→2KAMo2O7(A=Rb,Cs)+2CO2↑+4H2O↑

[0033] The third object of the present invention is achieved in this way:

[0034] The present invention aims to provide an alkali metal composite molybdate nonlinear optical crystal, wherein the chemical formula of the alkali metal composite molybdate nonlinear optical crystal is KAMo2O7 (A = Rb, Cs), wherein A = Rb, Cs has no symmetry center, belongs to the orthorhombic crystal system, has a space group Ama2, and has a unit cell parameter of Z=4.

[0035] The fourth object of the present invention is achieved in this way:

[0036] The alkali metal composite molybdate nonlinear optical crystal is prepared by a high-temperature melt method or an aqueous solution method.

[0037] The high-temperature melt method for growing nonlinear optical crystal KAMo2O7, wherein A=Rb, Cs, and the molecular formulas are KRbMo2O7 and KCsMo2O7, respectively, is specifically performed in the following steps:

[0038] a. Evenly mix two single-phase polycrystalline powders of alkali metal composite molybdate compounds with a flux, heat the mixture to a temperature of 350-800° C., maintain the temperature for a period of time to obtain a mixed melt, and then cool the mixture to a temperature of 300-750° C., wherein the molar ratio of the two single-phase polycrystalline powders of alkali metal composite molybdate compounds to the flux is 1:0-20;

[0039] Alternatively, a mixture of a potassium-containing compound, an A=Rb, Cs-containing compound, and a molybdenum-containing compound, or a mixture of a potassium-containing compound, an A=Rb, Cs-containing compound, and a molybdenum-containing compound and a flux is directly heated to a temperature of 350-800° C., kept constant for a period of time to obtain a mixed melt, and then cooled to a temperature of 300-750° C., wherein the molar ratio of the potassium-containing compound, the A=Rb, Cs-containing compound, the molybdenum-containing compound, and the flux is 0.5-1.5:0.5-1.5:1.5-2.5:0-20;

[0040] The flux mainly includes alkali metal salts, namely alkali metal carbonates, alkali metal nitrates, alkali metal sulfates, alkali metal oxalates, alkali metal borates, alkali metal phosphates, alkali metal halides, alkali metal oxides, alkali metal hydroxides, and at least one or more of monohydrogen molybdate, dihydrogen molybdate, boron oxide, boric acid, molybdic acid, lead oxide, lead fluoride, molybdenum oxide, and bismuth oxide.

[0041] The single-phase polycrystalline powder of the alkali metal composite molybdate compound is prepared by a solid-phase synthesis method, comprising the following steps: mixing a potassium-containing compound, a compound containing A=Rb, Cs, and a molybdenum-containing compound, and adopting a solid-phase reaction method to prepare two examples of the alkali metal composite molybdate of the compound, wherein the molar ratio of the element potassium in the potassium-containing compound, the element A (A=Rb, Cs) in the compound containing A=Rb, Cs, and the element molybdenum in the molybdenum-containing compound is 0.5-1.5:0.5-1.5:1.5-2.5; the raw materials of the potassium-containing compound, the compound containing A=Rb, Cs, and the molybdenum-containing compound are uniformly mixed, ground, and placed in a muffle furnace, pre-calcined to remove moisture and gas in the raw materials, cooled to room temperature, taken out, ground, and placed in a muffle furnace for calcination, heated to 350-800° C., kept constant at this temperature for a period of time, cooled to room temperature, and taken out to obtain the single-phase polycrystalline powder of the alkali metal composite molybdate of the compound obtained by grinding.

[0042] b. Preparation of two alkali metal composite molybdate seed crystals: slowly cooling the mixed melt obtained in step a to room temperature, and spontaneously crystallizing to obtain two alkali metal composite molybdate seed crystals;

[0043] c. Place the crucible containing the mixed melt obtained in step a into a crystal growth furnace, fix the seed crystal obtained in step b on the seed crystal rod, lower the seed crystal from the top of the crystal growth furnace, preheat the seed crystal rod, lower the seed crystal until it contacts the surface of the mixed melt or melts back in the mixed melt, maintain the temperature for a period of time, and then slowly reduce the temperature to the saturation temperature;

[0044] d. Continue to slowly cool down and rotate the seed crystal rod to grow the crystal. After the single crystal grows to the desired size, lift the crystal from the surface of the mixed melt and slowly cool it to room temperature. Then, take the crystal out of the furnace to obtain two alkali metal composite molybdate nonlinear optical crystals.

[0045] The aqueous solution method for growing nonlinear optical crystal KAMo2O7, wherein A=Rb, Cs, is specifically performed in the following steps:

[0046] A potassium compound, an A=Rb, Cs compound, and a molybdenum compound were added to a beaker, followed by 0.1-400mL of deionized water. The solution was stirred until clear. The beaker was then placed on a heating plate and heated to 25-400°C. After a period of time, two alkali metal complex molybdate nonlinear optical crystals were obtained. To further grow the crystals, seed crystals of this series were suspended in the solution using a fine platinum wire. To minimize water evaporation, the beaker was covered with a polyethylene sheet punctured with several dozen millimeter-sized holes. After a period of time, two centimeter-sized alkali metal complex molybdate nonlinear optical crystals were removed from the solution.

[0047] The fifth purpose of the present invention is achieved in this way:

[0048] The alkali metal composite molybdate nonlinear optical crystal product has high purity, is easy to grow, transparent and unwrapped, and has advantages such as rapid growth, low cost, and easy production of large crystals. The resulting crystal has a relatively wide light transmission band, high hardness, good mechanical properties, is resistant to breakage and deliquesce, and is easy to process and store. The alkali metal composite molybdate nonlinear optical crystal obtained using the method of the present invention can be used as a nonlinear optical device, depending on the device application requirements. The device comprises a device that generates at least one beam of incident electromagnetic radiation through at least one nonlinear optical device to generate at least one beam of output radiation having a frequency different from the incident electromagnetic radiation. The nonlinear optical crystal is a KAMo2O7 (A=Rb, Cs) crystal, with molecular formulas of KRbMo2O7 and KCsMo2O7, respectively.

[0049] Compared with the prior art, the present invention has the following advantages and technical effects: The alkali metal composite molybdate compound of the present invention has a powder frequency-doubled effect approximately six times that of KDP (KH2PO4). The alkali metal composite molybdate nonlinear optical crystal obtained by the method of the present invention has a laser intensity six times that of KDP (KH2PO4) at room temperature using a Q-switched Nd:YAG laser as the light source, with an incident infrared wavelength of 1064 nm and an output green laser wavelength of 532 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0051] Figure 1 The XRD spectrum of the compound KRbMo2O7 powder prepared in Example 1 of the present invention is shown in FIG.

[0052] Figure 2 The XRD spectrum of the compound KCsMo2O7 powder prepared in Example 1 of the present invention is shown in FIG.

[0053] Figure 3 1 is a structural diagram of the KCsMo2O7 crystal grown in Example 1 of the present invention;

[0054] Figure 4 This is a working principle diagram of the nonlinear optical device made in the present invention, where 1 is the laser, 2 is the emitted light beam, 3 is the nonlinear optical crystal of alkali metal composite molybdate, 4 is the output light beam, and 5 is the filter. DETAILED DESCRIPTION

[0055] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0056] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0057] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0058] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0059] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0060] The technical solution of the present invention is further illustrated by the following examples.

[0061] Example 1

[0062] According to the reaction formula: K2CO3+A2CO3(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+2CO2↑, KAMo2O7(A=Rb,Cs) compound is synthesized:

[0063] K2CO3, A2CO3 (A=Rb, Cs), and MoO3 were weighed in a molar ratio of 1:1:4 and placed in a mortar, mixed and ground carefully, then placed in a Φ100mm×100mm open corundum crucible, placed in a muffle furnace, slowly heated to 350°C, kept constant temperature for 24 hours, cooled to room temperature, taken out and ground for a second time, placed in a muffle furnace, then heated to 350°C, kept constant temperature for 24 hours, cooled to room temperature, taken out and ground for a third time, placed in a muffle furnace, and kept constant temperature at 350°C for 48 hours. The ground alkali metal composite molybdate compound single-phase polycrystalline powder was taken out and obtained, and the product was subjected to X-ray analysis. Figure 1 is the XRD spectrum of compound KRbMo2O7 powder, Figure 2 The XRD spectrum of the compound KCsMo2O7 powder is shown in Figure 2. It can be seen that the obtained X-ray spectrum is consistent with the X-ray spectrum obtained from the single crystal structure of the alkali metal complex molybdate KAMo2O7 (A=Rb, Cs); Figure 3 1 is a structural diagram of the KCsMo2O7 crystal grown in Example 1 of the present invention;

[0064] The obtained alkali metal composite molybdate compound KAMo2O7 (A = Rb, Cs) single-phase polycrystalline powder was placed in an open platinum crucible of Φ80mm×80mm, heated to 550°C at a heating rate of 30°C / h, kept at this temperature for 3 hours to obtain a mixed melt, and then cooled to 410°C;

[0065] The temperature was slowly lowered to room temperature at a rate of 0.5°C / h to obtain alkali metal composite molybdate seed crystals by spontaneous crystallization;

[0066] Growing crystals in compound melts: The obtained KAMo2O7 (A=Rb, Cs) seed crystals were fixed on a seed crystal rod and lowered from the top of the crystal growth furnace. The seed crystals were preheated on the surface of the mixed melt for 10 minutes, immersed in the liquid surface, and melted back in the mixed melt. The temperature was kept constant for 30 minutes, and then the temperature was rapidly lowered to the saturation temperature of 405℃.

[0067] Then the temperature is lowered at a rate of 0.1°C / day, and the seed crystal rod is rotated at a speed of 10 rpm. After the crystal growth is completed, the crystal is separated from the liquid surface and the temperature is lowered to room temperature at a rate of 10°C / h to obtain a KAMo2O7 (A=Rb, Cs) crystal with a size of 48mm×35mm×30mm.

[0068] Example 2

[0069] According to the reaction formula: 2KNO3+A2CO3(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+2NO2↑+CO2↑+0.5O2↑, KAMo2O7(A=Rb,Cs) compound is synthesized:

[0070] KNO3, A2CO3 (A=Rb, Cs), and MoO3 are directly weighed in a molar ratio of 2:1:4, and the weighed raw materials are mixed with a flux A2CO3 (A=Rb, Cs)-MoO3 in a molar ratio of 1:4, wherein the molar ratio of A2CO3 to MoO3 is 3:5, and the mixture is placed in an open platinum crucible of Φ80mm×80mm, and the temperature is raised to 490°C, kept at this temperature for 60 hours to obtain a mixed melt, and then cooled to 410°C;

[0071] The temperature was slowly lowered to room temperature at a rate of 1.5°C / h to obtain alkali metal composite molybdate seed crystals by spontaneous crystallization;

[0072] The obtained KAMo2O7 (A=Rb, Cs) seed crystals were fixed on a seed crystal rod and unloaded from the top of the crystal growth furnace. The seed crystals were preheated on the surface of the mixed melt for 10 minutes, then immersed below the liquid surface to melt back in the mixed melt. The temperature was kept constant for 30 minutes and then rapidly cooled to the saturation temperature of 390℃.

[0073] Then slowly cool down the temperature at a rate of 1°C / day without rotating the seed crystal rod. After the crystal grows to the required size, lift the crystal from the melt surface and cool the temperature to room temperature at a rate of 20°C / h. Then take the crystal out of the furnace to obtain a KAMo2O7 (A=Rb, Cs) crystal with a size of 36mm×22mm×15mm.

[0074] Example 3

[0075] According to the reaction formula: 2KOH+A2CO3(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+H2O↑+CO2↑, KAMo2O7(A=Rb,Cs) compound is synthesized:

[0076] KOH, A2CO3 (A=Rb, Cs), and MoO3 are directly weighed in a molar ratio of 2:1:4, and the weighed raw materials are mixed with a flux KOH-MoO3 in a molar ratio of 1:3, wherein the molar ratio of KOH to MoO3 is 3:1, and the mixture is placed in an open platinum crucible of Φ80mm×80mm, and the temperature is raised to 400℃, kept at this temperature for 60 hours to obtain a mixed melt, and then the temperature is lowered to 380℃;

[0077] The temperature was slowly lowered to room temperature at a rate of 3.5°C / h to obtain alkali metal composite molybdate seed crystals by spontaneous crystallization;

[0078] The obtained KAMo2O7 (A=Rb, Cs) seed crystals were fixed on a seed crystal rod and unloaded from the top of the crystal growth furnace. The seed crystals were preheated on the surface of the mixed melt for 15 minutes, then immersed below the liquid surface to melt back in the mixed melt. The temperature was kept constant for 30 minutes and then rapidly cooled to the saturation temperature of 355℃.

[0079] Then slowly cool down at a rate of 3°C / day, rotate the seed crystal crucible at a speed of 5 rpm, and after the crystal grows to the required size, lift the crystal from the melt surface, cool the temperature to room temperature at a rate of 1°C / h, and then take the crystal out of the furnace to obtain a KAMo2O7 (A=Rb, Cs) crystal with a size of 25mm×24mm×10mm.

[0080] Example 4

[0081] According to the reaction formula: K2CO3+2AOH(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+H2O↑+CO2↑, KAMo2O7(A=Rb,Cs) compound is synthesized:

[0082] Weigh K2CO3, AOH (A = Rb, Cs), and MoO3 in a molar ratio of 1:2:4, mix the weighed raw materials with flux NaF in a molar ratio of 1:3, put them into an open platinum crucible of Φ80mm×80mm, heat to 470℃, keep the temperature constant for 72 hours to obtain a mixed melt, and then cool to 450℃;

[0083] The temperature was slowly lowered to room temperature at a rate of 5°C / h to obtain alkali metal composite molybdate seed crystals by spontaneous crystallization;

[0084] The obtained KAMo2O7 (A=Rb, Cs) seed crystals were fixed on a seed crystal rod and unloaded from the top of the crystal growth furnace. The seed crystals were preheated on the surface of the mixed melt for 25 minutes, partially immersed below the liquid surface, and melted back in the mixed melt. The temperature was kept constant for 25 minutes, and then the temperature was rapidly cooled to the saturation temperature of 445℃.

[0085] Then cool down at a rate of 0.5℃ / day, rotate the seed crystal rod at a speed of 30rpm, and after the crystal grows to the required size, lift the crystal from the melt surface, cool the temperature to room temperature at a rate of 35℃ / h, and then take the crystal out of the furnace to obtain KAMo2O7 (A=Rb, Cs) crystals with a size of 22mm×32mm×20mm.

[0086] Example 5

[0087] According to the reaction formula: KOH + AOH (A = Rb, Cs) + 2MoO3 → KAMo2O7 (A = Rb, Cs) + H2O↑, KAMo2O7 (A = Rb, Cs) compound is synthesized:

[0088] Weigh KOH, AOH (A = Rb, Cs), and MoO3 in a molar ratio of 1:1:2, mix the weighed raw materials with flux H2MoO4 in a molar ratio of 2:5, and put them into an open platinum crucible of Φ80mm×80mm. Heat to 450℃, keep constant temperature for 72 hours to obtain a mixed melt, and then cool to 430℃.

[0089] The temperature was slowly lowered to room temperature at a rate of 3°C / h to obtain alkali metal composite molybdate seed crystals by spontaneous crystallization;

[0090] The obtained KAMo2O7 (A=Rb, Cs) seed crystals were fixed on a seed crystal rod and unloaded from the top of the crystal growth furnace. The seed crystals were preheated on the surface of the mixed melt for 10 minutes, then immersed below the liquid surface to melt back in the mixed melt. The temperature was kept constant for 30 minutes and then rapidly cooled to the saturation temperature of 410℃.

[0091] Then slowly cool down at a rate of 2°C / day, rotate the seed crystal rod at a speed of 5 rpm, and after the crystal grows to the required size, lift the crystal from the melt surface, cool the temperature to room temperature at a rate of 1°C / h, and then take the crystal out of the furnace to obtain a KAMo2O7 (A=Rb, Cs) crystal with a size of 25mm×24mm×10mm.

[0092] Example 6

[0093] According to the reaction formula: K2MoO4+A2CO3(A=Rb,Cs)+3MoO3→2KAMo2O7(A=Rb,Cs)+CO2↑, KAMo2O7(A=Rb,Cs) compound is synthesized:

[0094] K2MoO4, A2CO3 (A=Rb, Cs), and MoO3 were weighed directly into a 10mL beaker in a molar ratio of 1:1:3. 0.1mL of deionized water was then added and stirred until the solution was clear. The beaker was then placed on a heating plate at a constant temperature of 25°C. After two days, the alkali metal complex molybdate nonlinear optical crystal was obtained. To further grow the crystal, a seed crystal was suspended in the solution using a fine platinum wire. To minimize water evaporation, the beaker was covered with a polyethylene sheet punctured with several dozen millimeter-sized holes. After three weeks, a centimeter-sized alkali metal complex molybdate nonlinear optical crystal was removed from the solution.

[0095] Example 7

[0096] According to the reaction formula: 2KNO3+A2CO3(A=Rb,Cs)+4MoO3→2KAMo2O7(A=Rb,Cs)+2NO2↑+CO2↑+0.5O2↑, KAMo2O7(A=Rb,Cs) compound is synthesized:

[0097] KNO₃, A₂CO₃ (A=Rb, Cs), and MoO₃ were weighed directly into a 1000mL beaker in a molar ratio of 2:1:4. 400mL of deionized water was then added and stirred until the solution was clear. The beaker was then placed on a heating plate and heated to 400°C. After seven days, the alkali metal complex molybdate nonlinear optical crystal was obtained. To further grow the crystal, a seed crystal was suspended in the solution using a fine platinum wire. To minimize water evaporation, the beaker was covered with a polyethylene sheet punctured with several dozen millimeter-sized holes. After five weeks, a centimeter-sized alkali metal complex molybdate nonlinear optical crystal was removed from the solution.

[0098] Example 8

[0099] According to the reaction formula: K2MoO4+A2MoO4(A=Rb,Cs)+2MoO3→2KAMo2O7(A=Rb,Cs), KAMo2O7(A=Rb,Cs) compound is synthesized:

[0100] K2MoO4, A2MoO4 (A=Rb, Cs), and MoO3 are directly weighed in a molar ratio of 1:1:2, and the weighed raw materials are mixed with flux AOH (A=K, Rb, Cs)-PbO in a molar ratio of 4:7, wherein the molar ratio of AOH (A=K, Rb, Cs) to PbO is 1:6, and the mixture is placed in an open platinum crucible of Φ80mm×80mm, and the temperature is raised to 350°C, kept constant for 60 hours to obtain a mixed melt, and then the temperature is lowered to 330°C;

[0101] The temperature was slowly lowered to room temperature at a rate of 3.5°C / h to obtain alkali metal composite molybdate seed crystals by spontaneous crystallization;

[0102] The obtained KAMo2O7 (A=Rb, Cs) seed crystals were fixed on a seed crystal rod and unloaded from the top of the crystal growth furnace. The seed crystals were preheated on the surface of the mixed melt for 15 minutes, then immersed below the liquid surface to melt back in the mixed melt. The temperature was kept constant for 30 minutes and then rapidly cooled to the saturation temperature of 315℃.

[0103] Then slowly cool down at a rate of 3°C / day, rotate the seed crystal rod at a speed of 5 rpm, and after the crystal grows to the required size, lift the crystal from the melt surface, cool the temperature to room temperature at a rate of 1°C / h, and then take the crystal out of the furnace to obtain a KAMo2O7 (A=Rb, Cs) crystal with a size of 25mm×24mm×10mm.

[0104] Example 9

[0105] According to the reaction formula: 2KCl+A2CO3(A=Rb,Cs)+4MoO3+0.5O2→2KAMo2O7(A=Rb,Cs)+

[0106] CO2↑+Cl2↑, synthesize KAMo2O7 (A=Rb, Cs) compound:

[0107] KCl, A2CO3 (A=Rb, Cs), and MoO3 are directly weighed as raw materials in a molar ratio of 2:1:4, and the weighed raw materials are mixed with a flux A2CO3 (A=K, Rb, Cs)-MoO3-PbO in a molar ratio of 5:2, wherein the molar ratio of A2CO3 (A=K, Rb, Cs), MoO3, and PbO is 5:16:16. The raw materials are placed in an open platinum crucible of Φ80mm×80mm, and the temperature is raised to 550°C, kept at this temperature for 60 hours to obtain a mixed melt, and then the temperature is lowered to 530°C;

[0108] The temperature was slowly lowered to room temperature at a rate of 3.5°C / h to obtain alkali metal composite molybdate seed crystals by spontaneous crystallization;

[0109] The obtained KAMo2O7 (A=Rb, Cs) seed crystals were fixed on the seed crystal rod and unloaded from the top of the crystal growth furnace. The seed crystals were preheated on the surface of the mixed melt for 15 minutes, immersed below the liquid surface, and melted back in the mixed melt. The temperature was kept constant for 30 minutes, and then the temperature was rapidly cooled to the saturation temperature of 515℃.

[0110] Then slowly cool down at a rate of 3°C / day, rotate the seed crystal rod at a speed of 5 rpm, and after the crystal grows to the required size, lift the crystal from the melt surface, cool the temperature to room temperature at a rate of 1°C / h, and then take the crystal out of the furnace to obtain a KAMo2O7 (A=Rb, Cs) crystal with a size of 25mm×24mm×10mm.

[0111] Example 10

[0112] According to the reaction formula: K2CO3+A2CO3(A=Rb,Cs)+4H2MoO4→2KAMo2O7(A=Rb,Cs)+2CO2↑+4H2O↑, KAMo2O7(A=Rb,Cs) compound is synthesized:

[0113] K2CO3, A2CO3 (A = Rb, Cs), and H2MoO4 were weighed directly into a 10mL beaker in a molar ratio of 1:1:4. 0.1mL of deionized water was then added and stirred until the solution was clear. The beaker was then placed on a heating plate and heated to 400°C. After seven days, the alkali metal complex molybdate nonlinear optical crystal was obtained. To further grow the crystal, a seed crystal was suspended in the solution using a fine platinum wire. To minimize water evaporation, the beaker was covered with a polyethylene sheet punctured with several dozen millimeter-sized holes. After five weeks, a centimeter-sized alkali metal complex molybdate nonlinear optical crystal was removed from the solution.

[0114] Example 11

[0115] A single crystal device is made by processing any KRbMo2O7 or KCsMo2O7 crystal obtained in Examples 1-10 in the phase matching direction. The working principle diagram of the nonlinear optical device is shown in FIG. Figure 4 , where 1 is the laser, 2 is the emitted light beam, 3 is the nonlinear optical crystal of alkali metal complex molybdate, 4 is the output light beam, 5 is the filter, according to the attached Figure 4 As shown, the crystal is installed at position 3. At room temperature, a Nd:YAG Q-switched laser light source with a wavelength of 1064nm is used as a pump source to inject into the KRbMo2O7, KCsMo2O7 nonlinear optical crystal 3, generating a frequency-doubled light with a wavelength of 532nm. The output beam 4 contains infrared light with a wavelength of 1064nm and frequency-doubled light of 532nm, which is filtered out by the filter 5 to obtain a laser with a wavelength of 532nm.

[0116] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An alkali metal complex molybdate compound, characterized in that The molecular formula of the alkali metal composite molybdate compound is KAMo2O7, wherein A=Rb or Cs.

2. A method for preparing the alkali metal composite molybdate compound according to claim 1, characterized in that: Prepared by solid phase reaction method.

3. The method for preparing the alkali metal composite molybdate compound according to claim 2, wherein: The following steps are involved: The specific operation of preparing the alkali metal complex molybdate compound by the solid phase reaction method is as follows: uniformly mixing a potassium-containing compound, a compound containing A=Rb, Cs, and a molybdenum-containing compound, grinding the mixture, calcining the mixture in a muffle furnace, and grinding the mixture to obtain a single-phase polycrystalline powder of the alkali metal complex molybdate compound, wherein the molar ratio of the element potassium in the potassium-containing compound, the element A in the compound containing A=Rb, Cs, and the element molybdenum in the molybdenum-containing compound is 0.5-1.5:0.5-1.5:1.5-2.5; The potassium-containing compound includes at least one of KOH, K2O and an alkali metal salt, and the alkali metal salt includes at least one of KF, KCl, KBr, KNO3, K2C2O4, K2CO3, KHCO3, K2SO4, and K2MoO4; The compound containing A=Rb, Cs includes at least one of AOH, A2O, and an alkali metal salt, and the alkali metal salt includes at least one of AF, ACl, ABr, ANO3, A2C2O4, A2CO3, AHCO3, A2SO4, and A2MoO4; The molybdenum-containing compound includes at least one of MoO3, H2MoO4 and molybdate; the molybdate includes X2MoO4, XHMoO4, X6Mo7O 24 At least one of wherein X is K, Rb, Cs or NH4.

4. An alkali metal composite molybdate nonlinear optical crystal, characterized in that: The crystal chemical formula is KAMo2O7, wherein A is Rb or Cs, and the crystal belongs to the orthorhombic system, space group Ama2, and the unit cell parameters are Z=4.

5. The method for preparing the alkali metal composite molybdate nonlinear optical crystal according to claim 4, characterized in that: The alkali metal composite molybdate nonlinear optical crystal is grown by adopting a high-temperature melt method and an aqueous solution method.

6. The method for preparing the alkali metal composite molybdate nonlinear optical crystal according to claim 5, characterized in that: The following steps are involved: The specific operation of growing nonlinear optical crystals by the high-temperature melt method is as follows: heating a mixture of single-phase polycrystalline powder of an alkali metal composite molybdate compound or the single-phase polycrystalline powder of an alkali metal composite molybdate compound obtained according to claim 3 and a flux, or directly heating a mixture of a potassium-containing compound, an A=Rb, Cs-containing compound and a molybdenum-containing compound, or a mixture of a potassium-containing compound, an A=Rb, Cs-containing compound and a molybdenum-containing compound and a flux until it melts to obtain a mixed melt; then placing a crucible containing the mixed melt in a crystal growth furnace, heating it, and cooling it to a saturation temperature point, at which time extending a seed crystal rod below the liquid surface, and then lifting the seed crystal rod out of the liquid surface before the melt solidifies, thereby preparing the alkali metal composite molybdate nonlinear optical crystal; The specific operation of growing a nonlinear optical crystal using the aqueous solution method is as follows: adding a single-phase polycrystalline powder of an alkali metal complex molybdate compound, or a mixture of the single-phase polycrystalline powder of an alkali metal complex molybdate compound obtained in claim 3, and a solvent, or directly adding a mixture of a potassium-containing compound, an A=Rb, Cs-containing compound, and a molybdenum-containing compound, or a mixture of a potassium-containing compound, an A=Rb, Cs-containing compound, and a molybdenum-containing compound and a solvent to a beaker; then adding deionized water to dissolve the mixture, and stirring the solution until it becomes clear. The beaker is then exposed to air to evaporate the solution, thereby growing the alkali metal complex molybdate nonlinear optical crystal.

7. The method for preparing the alkali metal composite molybdate nonlinear optical crystal according to claim 6, characterized in that: In the high-temperature melt method for growing nonlinear optical crystals, the molar ratio of the alkali metal composite molybdate compound single-phase polycrystalline powder to the flux is 1:0-20; or the molar ratio of the potassium-containing compound, the A=Rb, Cs-containing compound, and the molybdenum-containing compound to the flux is 0.5-1.5:0.5-1.5:1.5-2.5:0-20; the flux comprises alkali metal salts, namely, alkali metal carbonates, alkali metal nitrates, alkali metal sulfates, alkali metal oxalates, alkali metal borates, alkali metal phosphates, alkali metal halides, alkali metal oxides, alkali metal hydroxides, and at least one or more of monohydrogen molybdate, dihydrogen molybdate, boron oxide, boric acid, molybdic acid, lead oxide, lead fluoride, molybdenum oxide, and bismuth oxide; The molar ratio of the alkali metal composite molybdate compound single-phase polycrystalline powder to the cosolvent is 1:0-30; or the molar ratio of the potassium-containing compound, the A=Rb,Cs-containing compound and the molybdenum-containing compound to the cosolvent is 0.8-1.2:0.8-1.2:1.8-2.2:0-30, and the cosolvent is a self-solvent.

8. A nonlinear optical device comprising means for passing at least one incident electromagnetic radiation through at least one nonlinear optical crystal to generate at least one output radiation having a frequency different from that of the incident electromagnetic radiation, wherein: The nonlinear optical crystal in the nonlinear optical device is the alkali metal composite molybdate nonlinear optical crystal KAMo2O7 as claimed in claim 4, wherein A=Rb, Cs.

9. Use of the alkali metal composite molybdate nonlinear optical crystal according to claim 4 in the preparation of a multi-band frequency doubling device or optical element.

10. The application according to claim 9, characterized in that: The alkali metal composite molybdate nonlinear optical crystal is used for preparing a second harmonic generator, an upper frequency converter, a lower frequency converter, an optical parametric oscillator, a laser frequency conversion device and a laser communication nonlinear optical device.

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