A type containing d 10 Transition metal phosphorus mixed anionic compound crystals, their preparation methods and applications

Abstract

This application discloses a method containing d 10 Phosphorus-containing mixed anionic compound crystals of transition metals, their preparation methods, and applications belong to the field of infrared second-order nonlinear optical crystal materials technology. The d-containing... 10 The unique chemical formula of the transition metal phosphorus mixed anionic compound crystal is AM4PnX6; where A is selected from Cs, Rb, K, Na, and Li; M is selected from Hg, Cd, and Zn; Pn is selected from P, As, and Sb; and X is selected from Cl, Br, and I. This crystal exhibits a nonlinear optical property (NLO) 29.6–52.3 times that of commercial AgGaS2, satisfies Class I phase matching, has a laser damage threshold 8.6–15.3 times that of commercial AgGaS2, a band gap of 2.4–3.3 eV, and a powder infrared transmission range of 0.4–25.0 μm, demonstrating excellent infrared nonlinear optical properties. It is a novel infrared nonlinear optical material.

Description

Technical Field

[0001] This application relates to a substance containing d 10 Phosphorus-based mixed anionic compound crystals of transition metals, their preparation methods, and applications belong to the field of infrared second-order nonlinear optical crystal materials technology. Background Technology

[0002] In recent years, infrared nonlinear optical crystals (NLOs) have attracted widespread attention due to their application in generating mid- and far-infrared tunable lasers through second harmonic generation and cascaded frequency conversion. Simultaneously, with continuous technological advancements, the demand for self-frequency doubling crystals and frequency-doubling crystals, as well as their wavelength application range and frequency doubling effects, is increasing. Currently, lasers in specific wavelength bands used in practical applications are obtained by frequency conversion of the fundamental frequency laser using a frequency-doubling crystal. Although significant progress has been made in crystal growth, processing, and applications of frequency-doubling crystal materials such as LiB3O5 (LBO), β-BaB2O4 (β-BBO), KH2PO4 (KDP), KTiOPO4 (KTP), AgGaS2 (AGS), and ZnGeP2 (ZGP), these crystals still cannot meet the demands of technological development. To date, commercially available infrared NLO crystals AgGaS2, AgGaSe2, and ZnGeP2 exhibit a significant second harmonic generation (SHG) effect due to their chalcopyrite structure, which is beneficial for NLOs. Therefore, the design and synthesis of novel IR-NLO materials that balance large SHG effect (>1×AGS) and moderate bandgap (preferably >2.33eV to avoid two-photon absorption of 1064nm laser) is of great importance in the field of nonlinear optics. Summary of the Invention

[0003] To provide a novel mid-to-far-infrared nonlinear optical crystal that balances a medium bandgap and a large SHG effect, this application provides a series of d-containing... 10 Phosphorus-containing mixed anionic compound crystals of transition metals can greatly improve the narrow band gap of phosphorus compounds by introducing halogens into them, while retaining the inherent advantage of strong SHG signals.

[0004] The technical solution adopted in this application is as follows:

[0005] According to the first aspect of this application, a method containing d is provided. 10 Transition metal phosphorus mixed anionic compound crystals, wherein the d-containing 10 The unique chemical formula of phosphorus-containing mixed anionic compounds of transition metals is AM4PnX6.

[0006] A is selected from one of Cs, Rb, K, Na, and Li;

[0007] M is selected from one of the elements Hg, Cd, and Zn;

[0008] Pn is selected from one of P, As, and Sb;

[0009] X is selected from one of Cl, Br, and I.

[0010] Optionally, the one containing d 10 Phosphorus-containing mixed anionic compounds of transition metals belong to the monoclinic crystal system, with space group Pm.

[0011] Optionally, the one containing d 10 The unit cell parameters of phosphorus mixed anionic compounds of transition metals are: α=90°, β=90°, γ=90-91°, Z = 1.

[0012] Optionally, the one containing d 10 Phosphorus-containing mixed anionic compound crystals of transition metals are host-guest compounds and have a non-centrosymmetric structure.

[0013] The main body of the host-guest entity is centered on the M atom. Each M atom is coordinated with 3 X atoms and 1 Pn atom to form a [MPnX3] tetrahedral unit. Every 3 [MPnX3] units are connected by sharing a vertices through Pn atoms to form a planar triangular trimer. The top of the trimer is connected to 1 [MPnX3] unit by sharing an X atom. The above 4 [MPnX3] tetrahedra together form a T2 super tetrahedron. Several T2 super tetrahedra are connected end to end to form a three-dimensional channel-like 3D Cd-P / I main body framework. The cross-sectional shape of the channel is approximately equilateral triangle and is composed of 6 [MPnX3] tetrahedra.

[0014] A + As an object, it fills the structure of the three-dimensional channel.

[0015] Optionally, the one containing d 10 Transition metal phosphorus mixed anionic compound crystals possess at least one of the following properties:

[0016] (1) The harmonics are 29.6-52.3 times that of AGS, and all are phase matched;

[0017] (2) The laser damage threshold is 8.6-15.3 times that of AgGaS2;

[0018] (3) The band gap value is 2.4-3.3 eV;

[0019] (4) The infrared transmission range of the powder is 0.4-25.0μm.

[0020] According to the first aspect of this application, a method containing the above-mentioned d is provided. 10 A method for preparing phosphorus-containing mixed anionic compounds of transition metals includes the following steps:

[0021] A mixture comprising source A, source M, source Pn, and source X is placed under vacuum, heated, and then cooled to obtain the substance containing d. 10 Phosphorus-containing mixed anionic compound crystals of transition metals.

[0022] Optionally, the molar ratio of A, M, Pn and X in the mixture is (1-4):(1-4):(1-2):(2-9).

[0023] Preferably, source A is selected from AX;

[0024] The source M is selected from at least one of elemental M, M3Pn2, and MX2;

[0025] The Pn source is selected from at least one of elemental Pn and M3Pn2;

[0026] X source is selected from at least one of MX2 and AX.

[0027] Optionally, the heating reaction conditions include: heating to 300-900°C at a rate of 30-50°C / h, and then holding at that temperature for 24-72h.

[0028] Optionally, the vacuum conditions include a vacuum degree of 10. -1 -10 -2 Pa.

[0029] Optionally, the cooling conditions include: cooling to 300°C at a rate of 1-10°C / h and then naturally cooling to room temperature.

[0030] According to a third aspect of this application, a method is provided that contains the above-mentioned d 10 Transition metal phosphorus mixed anionic compound crystals or d-containing compounds obtained according to any of the above preparation methods 10 Application of transition metal phosphorus-based mixed anionic compound crystals as infrared nonlinear optical materials in the field of optics.

[0031] The beneficial effects that this application can produce include:

[0032] This application provides d 10Phosphorus-based mixed anionic compounds of transition metals exhibit a nonlinear optical locus (NLO) 29.6–52.3 times that of commercial AgGaS2, satisfying Class I phase matching; their laser damage threshold is 8.6–15.3 times that of commercial AgGaS2; their band gap is 2.4–3.3 eV; and their powder infrared transmission range is 0.4–25.0 μm. This series of compounds possesses excellent infrared nonlinear optical properties, representing a novel type of infrared nonlinear optical material. This application significantly improves the narrow band gap of phosphorus compounds by introducing halogens, with CsCd4PI6 achieving a band gap of 3.0 eV, the highest reported among cadmium-based phosphorus compounds to date. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the inorganic compound crystal CsCd4PI6.

[0034] Figure 2 This is a schematic diagram of the structure of the inorganic compound crystal CsCd4AsI6.

[0035] Figure 3 This is a schematic diagram of the structure of the inorganic compound crystal RbCd4PI6.

[0036] Figure 4 To compare the simulated X-ray diffraction pattern obtained from the X-ray diffraction analysis of CsCd4PI6 single crystal with the experimental X-ray diffraction pattern obtained after grinding CsCd4PI6 into powder, the crystal structure was analyzed by X-ray diffraction analysis.

[0037] Figure 5 To compare the simulated X-ray diffraction pattern obtained by fitting the crystal structure determined by X-ray diffraction of CsCd4AsI6 single crystal with the experimental X-ray diffraction pattern obtained by grinding CsCd4AsI6 into powder.

[0038] Figure 6 To compare the simulated X-ray diffraction pattern obtained from the X-ray diffraction analysis of RbCd4PI6 single crystal with the experimental X-ray diffraction pattern obtained after RbCd4PI6 sample was ground into powder, the crystal structure was analyzed by X-ray diffraction analysis.

[0039] Figure 7 The results of frequency doubling tests of samples CsCd4PI6, CsCd4AsI6, and RbCd4PI6 against commercial AgGaS2 are shown.

[0040] Figure 8 The results are the infrared spectra of the CsCd4PI6 powder sample.

[0041] Figure 9The results are infrared spectra of CsCd4AsI6 powder samples.

[0042] Figure 10 The results are the infrared spectra of the RbCd4PI6 powder sample.

[0043] Figure 11 The diffuse reflectance spectra of CsCd4PI6 powder samples are shown.

[0044] Figure 12 The diffuse reflectance spectra of CsCd4AsI6 powder samples are as follows.

[0045] Figure 13 The diffuse reflectance spectra of the RbCd4PI6 powder sample are shown. Detailed Implementation

[0046] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0047] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0048] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0049] The following instruments, equipment, and methods were used in the testing in this application:

[0050] Single-crystal X-ray diffraction: equipped with monochromatic Mo-Kα radiation Single-crystal X-ray diffraction (SC-XRD) data were collected on a Rigaku FR-X microfocus diffractometer at a test temperature of 293 K. Data integration and reconstruction were performed using CrysAlisPro software. Intensity datasets were collected using the ω-scan technique, reconstructed using the Siemens SHELXTL crystallography software package, and the correctness of the structures was checked using the PLATON program.

[0051] Powder X-ray diffraction: Cu-Kα radiation in reflection mode on a Rigaku MiniFlex 600 diffractometer analyzer. Powder X-ray diffraction (PXRD) was measured. Measurements were performed in the range of 5 to 65° with a step size of 0.02° and a scan rate of 0.125° / min. -1 The test temperature was 293K.

[0052] Frequency doubling and laser damage threshold testing: AM4PnX6 and AGS crystals were sieved into several different particle size ranges (30-50, 50-75, 75-100, 100-150, and 150-200 μm) and then pressed into containers with a thickness of 1 mm and a diameter of 8 mm. Their NLO effects were then measured using a modified Kurtz-Perry NLO system under incident laser radiation at 1064, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1910, and 2000 nm. A positive correlation between nonlinear intensity and particle size indicates phase matching. Laser damage thresholds were measured on AM4PnX6 and AGS crystal surfaces of the same size (~3 mm) using a 1.06 μm laser beam (pulse width 10 ns, frequency 1 Hz) as the damage source.

[0053] Infrared transmission test: Infrared transmission spectroscopy was recorded on a Nicolet Magna 750FT-IR spectrometer, ranging from 4000 to 400 cm⁻¹. -1 The polycrystalline powder of AM4PnX6 was placed directly on the test platform to obtain the vibrational peaks in the infrared spectrum.

[0054] Bandgap testing: Optical diffuse reflectance spectra were performed at room temperature using a PerkinElmer Lamda-950UV / Vis / NIR spectrophotometer in the wavelength range of 200–2000 nm. BaSO4 plates were used as a 100% reflectance comparison standard. The reflectance values ​​were converted to absorbance using the Kubelka-Munk function, and the bandgap was estimated based on the absorption spectra.

[0055] According to one embodiment of this application, a novel infrared nonlinear optical material is a material containing d 10 A transition metal phosphorus-containing mixed anionic compound crystal with the chemical formula AM4PnX6, wherein A is selected from Cs, Rb, K, Na, and Li; M is selected from Hg, Cd, and Zn; Pn is selected from P, As, and Sb; and X is selected from a halogen. The d-containing element... 10 Phosphorus-containing mixed anionic compounds of transition metals have a non-centrosymmetric structure, space group Pm, and belong to the monoclinic crystal system. Their unit cell parameters are: α=90°, β=90°, γ=90-91°, Z = 1.

[0056] According to one embodiment of this application, including d 10 The preparation method of phosphorus-containing mixed anionic compound crystals of transition metals includes the following steps:

[0057] Elemental cadmium, elemental mercury, elemental zinc, phosphorus group elements, and d10 Transition metal phosphides, d 10 After the raw materials of transition metal halides and alkali metal halides are mixed evenly, they are placed in a quartz tube and evacuated to 10°C. -1 -10 -2 The Pa tube is sealed and placed in a muffle furnace, heated to 300-900℃ at a rate of 30-50℃ / h, held at this temperature for 24-72h, then cooled to 300℃ at a rate of 1-10℃ / h. The muffle furnace is then turned off and allowed to cool naturally to room temperature, yielding a compound with the chemical formula AM4PnX6. The raw material for M can be elemental M, a compound M3Pn2, or a compound MX2.

[0058] Example 1

[0059] Weigh out 300 mg of CsI, Cd, P, and CdI2 in a molar ratio of 1:3:2:1, mix thoroughly, and then place the mixture into a quartz tube and evacuate to 10°C. -2 The tube was sealed with Pa and placed in a muffle furnace. It was heated to 750°C over 20 hours and held at that temperature for 60 hours. After cooling to 300°C at a rate of 3°C / h, the muffle furnace was turned off and allowed to cool naturally to room temperature, yielding crystals with the chemical formula CsCd4PI6. The crystals were colorless and transparent.

[0060] Example 2

[0061] Weigh out 300 mg of CsI, Cd, As, and CdI2 in a molar ratio of 1:1:1:2, mix thoroughly, place in a quartz tube, and evacuate to 10°C. -2 The tube was sealed with Pa and placed in a muffle furnace. It was heated to 750°C over 20 hours and held at that temperature for 60 hours. After cooling to 300°C at a rate of 3°C / h, the muffle furnace was turned off and allowed to cool naturally to room temperature, yielding crystals with the chemical formula CsCd4AsI6. The crystals were yellow in color.

[0062] Example 3

[0063] Weigh out 300 mg of RbI, Cd, P, and CdI2 in a molar ratio of 1:1:2:2, mix thoroughly, and then place the mixture into a quartz tube and evacuate to 10°C. -2 The tube was sealed with Pa and placed in a muffle furnace. It was heated to 750°C over 20 hours and held at that temperature for 60 hours. After cooling to 300°C at a rate of 3°C / h, the muffle furnace was turned off and allowed to cool naturally to room temperature, yielding crystals with the chemical formula RbCd4PI6. The crystals were yellow in color.

[0064] Example 4

[0065] Weigh out 300 mg of CsI, Zn, P, and ZnI2 in a molar ratio of 2:1:2:1, mix thoroughly, and then place the mixture into a quartz tube and evacuate to 10°C. -2The tube was sealed with Pa and placed in a muffle furnace. It was heated to 750°C over 20 hours and held at that temperature for 60 hours. After cooling to 300°C at a rate of 3°C / hour, the muffle furnace was turned off and allowed to cool naturally to room temperature, yielding crystals with the chemical formula CsZn4PI6. The crystals were colorless and transparent.

[0066] Example 5

[0067] Weigh out 300 mg of CsBr, Cd, P, and CdBr2 in a molar ratio of 1:1:2:3, mix thoroughly, and then place the mixture into a quartz tube and evacuate to 10°C. -2 The tube was sealed with Pa and placed in a muffle furnace. It was heated to 750°C over 20 hours and held at that temperature for 60 hours. After cooling to 300°C at a rate of 3°C / h, the muffle furnace was turned off and allowed to cool naturally to room temperature, yielding crystals with the chemical formula CsCd4PBr6. The crystals were colorless and transparent.

[0068] Example 6

[0069] Weigh out 300 mg of CsI, P, and HgI2 in a molar ratio of 1:2:4, mix thoroughly, and then place the mixture into a quartz tube and evacuate to 10°C. -2 The tube was sealed with Pa and placed in a muffle furnace. It was heated to 500°C over 20 hours and held at that temperature for 60 hours. After cooling to 200°C at a rate of 3°C / h, the muffle furnace was turned off and allowed to cool naturally to room temperature, yielding crystals with the chemical formula CsHg4PI6. The crystals were yellowish-green in color.

[0070] Example 7

[0071] Weigh out 300 mg of KI, Cd3As2, and CdI2 in a molar ratio of 2:1:3, mix thoroughly, and then place the mixture into a quartz tube and evacuate to 10°C. -2 The tube was sealed with Pa and placed in a muffle furnace. It was heated to 750°C over 20 hours and held at that temperature for 60 hours. After cooling to 300°C at a rate of 3°C / h, the muffle furnace was turned off and allowed to cool naturally to room temperature, yielding crystals with the chemical formula KCd4AsI6. The crystals were yellow in color.

[0072] Test Example 1

[0073] Single-crystal X-ray diffraction and powder X-ray diffraction tests were performed on the crystals prepared in Examples 1 to 7, and the results are as follows:

[0074] The CsCd4PI6 crystal, space group Pm, belongs to the monoclinic crystal system, and its unit cell parameters are: α=90°, β=90.019°, γ=90°, Z = 1.

[0075] The CsCd4AsI6 crystal has space group Pm and belongs to the monoclinic crystal system. Its unit cell parameters are: α=90°, β=90.013°, γ=90°, Z = 1.

[0076] The crystal of RbCd4PI6 has space group Pm and belongs to the monoclinic crystal system. Its unit cell parameters are: α=90°, β=90.201°, γ=90°, Z = 1.

[0077] The CsZn4PI6 crystal has space group Pm and belongs to the monoclinic crystal system. Its unit cell parameters are: α=90°, β=90.012°, γ=90°, Z = 1.

[0078] The crystal of CsCd4PBr6 has space group Pm and belongs to the monoclinic crystal system. Its unit cell parameters are: α=90°, β=90.104°, γ=90°, Z = 1.

[0079] The crystal of CsHg4PI6 has space group Pm and belongs to the monoclinic crystal system. Its unit cell parameters are: α=90°, β=90.026°, γ=90°, Z = 1.

[0080] The crystal of KCd4AsI6 has space group Pm and belongs to the monoclinic crystal system. Its unit cell parameters are: α=90°, β=90.208°, γ=90°, Z = 1.

[0081] The structures of CsCd4PI6, CsCd4AsI6, and RbCd4PI6 are as follows: Figures 1-3 As shown, based on the crystal structure resolved by single-crystal X-ray diffraction, the fitted X-ray diffraction pattern (simulated value) is compared with the X-ray diffraction pattern (experimental value) obtained after grinding CsCd4PI6, CsCd4AsI6 and RbCd4PI6 into powder. Figure 4-6 As shown in the figure, the position and intensity of the peaks are consistent, indicating that the obtained sample has high purity.

[0082] The crystalline compounds prepared in Examples 1 to 7 are host-guest compounds with a non-centrosymmetric structure. Taking the crystal with the chemical formula CsCd4PI6 prepared in Example 1 as an example, the main body can be considered as a Cd atom at the center, with each Cd atom coordinated with 3 I atoms and 1 P atom to form a [CdPI3] tetrahedral unit. Every 3 [CdPI3] units are connected by sharing a P atom at their vertices to form a planar triangular trimer. At the top of these trimers, another [CdPI3] unit is connected by sharing an I atom. These 4 [CdPI3] tetrahedra together form a T2 supertetrahedron. These T2 supertetrahedra are connected end-to-end, forming a porous 3D Cd-P / I main framework in three-dimensional space. It can be clearly seen from the a-axis direction that the planar shape of each main cavity is approximately an equilateral triangle, composed of 6 [CdPI3] tetrahedra. + As an object, it fills the three-dimensional porous structure.

[0083] Test Example 2

[0084] Using the crystal powders prepared in Examples 1 to 3 as typical examples, frequency doubling tests, infrared spectroscopy tests, band gap tests, and laser damage threshold tests were performed on the crystal powders prepared in Examples 1 to 3 and the AGS polycrystalline powder. The results are as follows:

[0085] Figure 7 The results show the frequency doubling test results for samples CsCd4PI6, CsCd4AsI6, and RbCd4PI6. The results indicate that under 1064nm laser irradiation, when the particle size is 150-200μm, the powder frequency doubling coefficient is 29.6-52.3 times that of AGS, and all are phase-matched.

[0086] Figure 8-10 Infrared spectral analysis results for CsCd4PI6, CsCd4AsI6, and RbCd4PI6 powder samples are shown. The results indicate that the infrared transmission range of the series of compounds is 0.5–25.0 μm.

[0087] Figure 11-13 The diffuse reflectance spectra of CsCd4PI6, CsCd4AsI6, and RbCd4PI6 powder samples are shown. The results indicate that the band gaps of compounds CsCd4PI6, CsCd4AsI6, and RbCd4PI6 are 3.00 eV, 2.69 eV, and 2.76 eV, respectively.

[0088] Table 1 shows the comparison of the laser damage resistance thresholds of AM4PnX6 and AGS polycrystalline powder. It can be seen that the laser damage resistance threshold of AM4PnX6 is 8.6-15.3 times that of AgGaS2.

[0089] Table 1

[0090]

[0091] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A substance containing d 10 Transition metal phosphorus mixed anionic compound crystals, characterized by, The d- 10 The unique chemical formula of phosphorus-containing mixed anionic compounds of transition metals is AM4PnX6. A is selected from one of Cs, Rb, K, Na, and Li; M is selected from one of the elements Hg, Cd, and Zn; Pn is selected from one of P, As, and Sb; X is selected from one of Cl, Br, and I; The d- 10 Phosphorus-containing mixed anionic compounds of transition metals belong to the monoclinic crystal system, space group 1. Pm .

2. The d-containing [material] according to claim 1 10 Transition metal phosphorus mixed anionic compound crystals, characterized by, The d- 10 Phosphorus-containing mixed anionic compound crystals of transition metals are host-guest compounds and have a non-centrosymmetric structure. The main body of the host-guest entity is centered on the M atom. Each M atom is coordinated with 3 X atoms and 1 Pn atom to form a [MPnX3] tetrahedral unit. Every 3 [MPnX3] units are connected by sharing a vertices through Pn atoms to form a planar triangular trimer. The top of the trimer is connected to 1 [MPnX3] unit by sharing an X atom. The above 4 [MPnX3] tetrahedra together form a T2 super tetrahedron. Several T2 super tetrahedra are connected end to end to form a three-dimensional channel-like 3D Cd-P / I main body framework. The shape of the channel cross section is approximately equilateral triangle and is composed of 6 [MPnX3] tetrahedra. A + As an object, it fills the structure of the three-dimensional channel.

3. The d-containing [material] according to claim 1 10 Transition metal phosphorus mixed anionic compound crystals, characterized by, The d- 10 Transition metal phosphorus-containing mixed anionic compound crystals possess at least one of the following properties: (1) The harmonics are 29.6–52.3 times that of AGS, and all are phase matched; (2) The laser damage threshold is 8.6–15.3 times that of AgGaS2; (3) The band gap value is 2.4–3.3 eV; (4) The infrared transmission range of the powder is 0.4–25.0 μm.

4. The d-containing compound as described in any one of claims 1 to 3 10 A method for preparing phosphorus-containing mixed anionic compound crystals of transition metals, characterized in that, Includes the following steps: A mixture comprising source A, source M, source Pn, and source X is placed under vacuum, heated, and then cooled to obtain the substance containing d. 10 Phosphorus-containing mixed anionic compound crystals of transition metals.

5. The preparation method according to claim 4, characterized in that, In the mixture, the molar ratio of A, M, Pn and X is (1~4):(1~4):(1~2):(2~9).

6. The preparation method according to claim 4, characterized in that, The source A is selected from AX; The source M is selected from at least one of elemental M, M3Pn2, and MX2; The Pn source is selected from at least one of elemental Pn and M3Pn2; X source is selected from at least one of MX2 and AX.

7. The preparation method according to claim 4, characterized in that, The conditions for the heating reaction include: heating to 300-900℃ at a rate of 30-50℃ / h, and then holding at that temperature for 24-72h.

8. The preparation method according to claim 4, characterized in that, The vacuum conditions include a vacuum degree of 10. -1 -10 - 2 Pa.

9. The preparation method according to claim 4, characterized in that, The cooling conditions include: cooling to 300°C at a rate of 1-10°C / h, followed by natural cooling to room temperature.

10. The d-containing compound as described in any one of claims 1 to 3 10 Transition metal phosphorus mixed anionic compound crystals or d-containing compounds obtained by the preparation method according to any one of claims 4 to 9 10 Application of transition metal phosphorus-based mixed anionic compound crystals as infrared nonlinear optical materials in the field of optics.

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