Holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and preparation method thereof

Abstract

The invention relates to a holmium and praseodymium doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof, the chemical formula of the crystal is Ho, Pr: Me1Me2CaSrBaF12, the doping concentration of holmium is 0.5-1.5 at.%, the doping concentration of praseodymium is 0.05-0.15 at.%, and Me1 and Me2 are respectively selected from one of lanthanum, yttrium, gadolinium, scandium, lutetium, aluminum and gallium. Compared with the prior art, the invention has the advantages of wide absorption range, high transmittance and mid-infrared laser output capability with high fluorescence intensity.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser materials and preparation thereof, and relates to a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof. Background Art

[0002] High-entropy materials (HEMs) are single-phase solid solution materials composed of multiple main elements (usually ≥5) in equimolar or nearly equimolar proportions. Their core feature is high mixing entropy (ΔS mix >1.5R, where R is the gas constant), and a stable structure formed by the uniform distribution of multiple elements, rather than a single main element or simple compound phase in traditional materials. The core properties of high-entropy materials stem from the thermodynamic stability, lattice distortion, hysteresis diffusion, and "cocktail effect" brought about by high mixing entropy. It can be applied in the following aspects:

[0003] 1. In the energy sector, high-entropy materials have significantly improved battery performance by optimizing element combinations. For example, when used as negative electrodes in lithium-ion batteries, high-entropy oxides (HEOs) can increase discharge capacity to over 1500 mAh / g and enhance cycling stability by suppressing volume expansion and intercrystalline fracture. High-entropy catalysts, due to the synergistic effect of multiple elements, exhibit efficient catalytic activity in reactions such as hydrogen evolution and oxygen reduction.

[0004] 2. In electronic applications, the lattice distortion and chemical disorder of high-entropy materials reduce thermal conductivity, while improving electrical conductivity by manipulating the electronic structure, making them potential in thermoelectric materials and radiation-resistant devices;

[0005] 3. In addition, high entropy ceramics (HECs) have become key candidate materials for aviation engines and nuclear energy equipment due to their high temperature resistance (melting point over 1650°C) and corrosion resistance.

[0006] Although high-entropy materials have significant advantages in composition flexibility and performance adjustability, their large-scale application still faces challenges such as complex preparation processes, difficulty in optimizing element ratios, and insufficient verification of long-term stability. It is necessary to promote breakthroughs in high-entropy materials in fields such as energy storage, electronic devices, and extreme environment engineering.

[0007] Mid-infrared lasers (2-25 μm) have a wide range of applications in the fields of medicine (non-invasive ophthalmic surgery, dental ablation), communications (laser communications), environmental monitoring (real-time pollutant detection), material processing (micro-nano processing), and basic science (ultrafast molecular dynamics research). Their core depends on the energy level characteristics of specific activated ions. Typical activated ions include Er 3+ (Erbium ions, 2.7-3 μm, suitable for laser surgery and methane detection), Ho 3+(holmium ions, 2.7-3.2 μm, used for lidar and aerosol detection), Cr 2+ (chromium ions, 2-3 μm, suitable for spectral analysis and high-power pumping), Fe 2+ (iron ions, 3-5 μm, used for infrared countermeasures) and Dy 3+ (Dysprosium ions, 2.9-4.3 μm, used for carbon dioxide detection).

[0008] Patent CN116145254A discloses a rare earth ion doped disordered high entropy fluoride ultrafast laser crystal and its preparation method and application. The disordered high entropy laser crystal is composed of Pr:CaSrBaF6, Pr:M1M2CaSrBaF 12 is represented by, wherein the doping range of Pr ions is 0.003~0.05 (M1, M2 are one of trivalent non-luminescent ions such as Y, La, Lu, Gd, Sc); the doped rare earth luminescent ions are not limited to Pr ions, but can also include other luminescent ions such as Yb, Nd, Er, Ho, Tm, Dy, Tb, etc.; wherein, the preparation method includes the following steps: using PrF3, YF3, LaF3, CaF2, SrF2 and BaF2 single crystal particles or powders as raw materials, according to the doping concentration of praseodymium ions of 0.003~0.05, the required mass of each raw material is calculated according to the chemical formula and accurately weighed; the weighed raw materials are fully ground to make them mixed evenly, and then loaded into a graphite crucible and covered with a crucible lid; the loaded graphite crucible is placed in a hot field for vacuuming, inert gas is filled into the furnace, the temperature is increased to ensure complete chemical reaction and impurity removal, and then the temperature is slowly reduced to grow the crystal, and after the growth is completed, the temperature is lowered to room temperature, and then the crystal is taken out. However, the main laser application band of the praseodymium ion in this patent is in the visible light range, and it lacks the ability to emit light in the infrared band.

[0009] Patent CN103194796A discloses a holmium-praseodymium co-doped lithium lutetium fluoride mid-infrared laser crystal and its preparation method. The holmium-praseodymium co-doped lithium lutetium fluoride laser crystal is grown using the Czochralski method, employing lithium lutetium fluoride as the matrix material, holmium ions as activating ions, and praseodymium ions as deactivating ions. However, the patent's crystal growth method, using the Czochralski method, results in only one crystal being grown per batch. Furthermore, the crystal size is limited by the crucible and coil sizes, making high-throughput crystal growth impossible. Furthermore, the lithium lutetium fluoride laser crystal has a low melting point and poor thermal conductivity, making it prone to heat accumulation during high-power laser operation, affecting laser efficiency and causing crystal cracking. Summary of the Invention

[0010] The purpose of the present invention is to overcome at least one of the defects of the above-mentioned prior art and to provide a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof. The present invention has a wide absorption range and high transmittance, as well as a mid-infrared laser output capability with high fluorescence intensity.

[0011] The purpose of the present invention can be achieved by the following technical solutions:

[0012] One of the technical solutions of the present invention is to provide a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal, the chemical formula of which is Ho,Pr:Me1Me2CaSrBaF 12 , among which Ho 3+ As the active ion for luminescence in the mid-infrared band, the doping concentration of holmium (Ho) is 0.5-1.5 at.%, Pr 3+ As Ho 3+ The deactivation ion, the doping concentration of praseodymium (Pr) is 0.05~0.15at.%, ​​and the Me1 3+ and Me2 3+ As the non-luminescent ions, Me1 and Me2 are each selected from one of lanthanum (La), yttrium (Y), gadolinium (Gd), scandium (Sc), lutetium (Lu), aluminum (Al), and gallium (Ga).

[0013] As a preferred technical solution, the structure of the crystal belongs to the cubic system, the space group is Fm-3m (225), and the unit cell parameters are

[0014] One of the technical solutions of the present invention is to provide a method for preparing the holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal, which comprises the following steps:

[0015] S1. Grind and mix the metal raw materials of the crystal according to the stoichiometric ratio;

[0016] S2. Evacuate the chamber and maintain the vacuum during the entire crystal growth process. The vacuum environment helps to remove moisture and oxygen in the raw materials and the crystal growth furnace, which are unfavorable factors for crystal growth. It also helps to remove volatile impurities in the melt after the raw materials are melted. Heat the raw materials to melt and remove impurities.

[0017] S3. Slowly cool the crystal growth to ensure sufficient crystal growth and eliminate thermal stress, and quickly cool the crystal to avoid the low melting point impurities affecting the crystal quality due to too long time in the high temperature zone after the crystal growth is completed, thereby obtaining a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal.

[0018] Furthermore, in step S1, the holmium raw material of the crystal is holmium fluoride (HoF3), the praseodymium raw material is praseodymium fluoride (PrF3), the strontium raw material is strontium fluoride (SrF3), the calcium raw material is calcium fluoride (CaF2), the barium raw material is barium fluoride (BaF2), and the raw materials of Me1 and Me2 are the fluoride salts of Me1 and Me2 (Me1F3 and Me2F3), respectively.

[0019] Furthermore, a water and oxygen remover is added before grinding in step S1. The water and oxygen remover can prevent the raw materials from reacting with the crucible due to the presence of water and oxygen at high temperatures, thereby preventing the quality of the crystal from being affected.

[0020] Furthermore, in step S1, the water-oxygen remover is lead fluoride (PbF2), and the mass fraction of the water-oxygen remover relative to the total mass of the metal raw materials of the crystal is 0.5-1.5 wt.%.

[0021] As a preferred technical solution, the state of the raw material in step S1 is selected from single crystal particles or powder, and the purity level is 99.99% (4N) or 99.999% (5N).

[0022] As a preferred technical solution, the particle size of the grinding in step S1 is 500-700 mesh.

[0023] The mixing time is 20 to 40 minutes.

[0024] As a preferred technical solution, in step S1, the reaction container of the raw materials is provided with vent holes, the diameter of the vent holes being 0.5 to 1.5 mm, and the vent holes are used to remove impurities during the crystal growth process.

[0025] Furthermore, the vacuum degree of the vacuum pumping in step S2 is 1×10 -2 Below Pa.

[0026] Furthermore, in step S2, the vacuum is firstly drawn to a low vacuum of 5-15 Pa using a mechanical pump, and then the vacuum is drawn to 1×10 -5 ~1×10 -3 Pa of high vacuum.

[0027] Furthermore, the heating rate of the temperature in step S2 is 400-500° C. / h, the target temperature is 1400-1500° C., and the constant temperature time is 10-20 h.

[0028] Furthermore, the cooling rate of the slow cooling in step S3 is 0.5-2°C / h, and the target temperature is 1000-1100°C.

[0029] Furthermore, the cooling rate of the rapid cooling in step S3 is 20-40°C / h, and the target temperature is 20-60°C.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention has a wide absorption capacity in the range of 400 to 2200 nm, a high transmittance, and a strong fluorescence intensity in the range of 1800 to 3200 nm;

[0032] (2) The unique properties of the high entropy material (multi-principal element disordered crystal) in the present invention can further amplify Ho 3+ The advantages of structural disorder enhance the emission bandwidth. The high configurational entropy of high entropy materials leads to lattice disorder, such as the addition of Gd into YGGAG crystals. 3+ and Ga 3+ etc., which results in non-uniform broadening of the fluorescence emission band (Er:YGGAG broadens in the 2786-2819 nm band). A similar mechanism can be applied to Ho 3+ Doped high entropy system to achieve a wider tunable range;

[0033] (3) The thermal management performance of the present invention is optimized. High entropy materials often have high thermal conductivity and resistance to thermal distortion. For example, by thermal bonding technology, undoped YSGG crystal is compounded with Er:YSGG, which can increase the continuous laser output power to 28.02W. 3+ The system is combined with a high-entropy matrix to alleviate thermal effects at high power and improve laser stability;

[0034] (4) In the present invention, the doping concentration and ions are coordinated and regulated. The compositional diversity of high entropy materials allows for a more flexible multi-ion co-doping strategy. For example, in Ho, Pr: YAP, by adjusting the Pr 3+ concentration (0.1 at.%), which can not only suppress the self-termination effect but also avoid excessive quenching of the upper energy level particles; the complex chemical environment of the high entropy system can also explore other cooperative ions (such as Gd 3+ Sc 3+ Co-doping effect of

[0035] (5) The present invention has mechanical and chemical stability. The strong lattice distortion of high entropy materials can improve mechanical strength. For example, YScO3 crystals have low phonon energy (about 400cm -1 ) and chemical stability, suitable as Ho 3+ This characteristic can extend the service life of laser devices and is especially suitable for high-demand scenarios such as biomedicine.

[0036] (6) Due to the presence of various lattices, the present invention makes Ho 3+ and Pr 3+The average ionic distance is reduced, which increases the energy transfer efficiency between ions. At the same time, the multi-component high entropy composition makes the entire system present a glass-like state, such as disordered structures such as ZBLAN and ZBYA. This result further reduces the overall phonon energy, thus achieving strong luminescence in the 3μm band.

[0037] (7) The present invention adopts a temperature gradient method for crystal growth, which can achieve high-throughput production of high-quality and large-sized holmium-praseodymium-doped disordered high-entropy fluoride laser crystals;

[0038] (8) The present invention can achieve efficient laser output in the mid-infrared band of 2 to 3 μm. The grown crystals have the characteristics of high chemical stability and high transmittance. At the same time, they have the advantages of high gain bandwidth, high gain cross section, high power and high slope efficiency in the mid-infrared band. They have significant advantages in the fields of space exploration, atmospheric detection, pollution monitoring, biomedicine, industrial processing, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a transmission spectrum of the holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal in Example 1 of the present invention;

[0040] Figure 2 This is an absorption spectrum of the holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal in Example 1 of the present invention;

[0041] Figure 3 This is a fluorescence spectrum of the holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal in Example 1 of the present invention. DETAILED DESCRIPTION

[0042] The present invention is described in detail below with reference to specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0043] Unless otherwise specified, the equipment used in the following examples are all conventional equipment in the art; the reagents used are all commercially available products or prepared by conventional methods in the art unless otherwise specified. Anything not described in detail in the following examples can be achieved by conventional experimental means in the art.

[0044] Example 1:

[0045] A holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof, the specific steps are as follows:

[0046] S1. Metal raw materials, using single crystal particles of 99.999% (5N) purity of holmium fluoride (HoF3), praseodymium fluoride (PrF3), strontium fluoride (SrF3), calcium fluoride (CaF2), barium fluoride (BaF2), lanthanum fluoride (LaF3) and gadolinium fluoride (GdF3) as crystals, according to the chemical formula 1at.% Ho, 0.1at.% Pr:LaGdCaSrBaF 12 Accurately weigh 150 g of raw materials with a total weight of the corresponding stoichiometric ratio, and weigh 1.5 g of lead fluoride (PbF2) with a total weight of 1 wt.% as a water-oxygen remover. The water-oxygen remover can prevent the raw materials from reacting with the crucible due to the presence of water and oxygen at high temperatures, thereby affecting the quality of the crystal. The various metal raw materials of the crystal and the water-oxygen remover are placed in an agate mortar with a particle size of 600 mesh and stirred for 30 minutes until the mixture is uniform. The mixture is transferred into a porous graphite crucible and covered with a crucible lid with a vent hole with a diameter of 1 mm in the center. The vent hole is used to remove impurities during the crystal growth process.

[0047] S2. Place the porous graphite crucible into the hot field. First, use a mechanical pump to pump the vacuum degree in the furnace chamber to a low vacuum of 10Pa. Then use a molecular pump to pump the vacuum degree in the furnace chamber to 1×10 -4 Pa high vacuum, and maintain high vacuum throughout the crystal growth process. The vacuum environment helps to eliminate factors that are unfavorable to crystal growth, such as moisture and oxygen in the raw materials and crystal growth furnace, and also helps to eliminate volatile impurities in the melt after the raw materials are melted. Start the power and increase the temperature to 1450℃ at a rate of 450℃ / h, and keep the temperature constant for 12h until the raw materials are fully melted and impurities are removed;

[0048] S3. Start the slow cooling process at a rate of 1.5°C / h to grow the crystal to ensure sufficient growth of the crystal and eliminate thermal stress. After cooling to 1050°C, start the fast cooling process at a rate of 30°C / h to avoid the low melting point impurities affecting the crystal quality due to too long time in the high temperature zone after the crystal growth is completed. After cooling to room temperature of 25°C, take out the crystal to obtain a holmium-praseodymium-doped disordered high entropy fluoride mid-infrared laser crystal.

[0049] like Figure 1 As shown, it can be seen that the crystal in Example 1 is free of Ho 3+ and Pr 3+ In addition to the characteristic absorption peak, the effective transmittance in the visible and infrared bands is above 90%, which proves that the crystal has extremely high crystal quality. At the same time, the ultraviolet cutoff edge of the crystal is <200nm, so the crystal in the embodiment is expected to be suitable for application in the deep ultraviolet and extreme ultraviolet ranges.

[0050] like Figure 2As shown, it can be seen that the crystal in Example 1 has a wide absorption capacity in the range of 400 to 2200 nm, for example, it has multiple strong absorption peaks in the range of 400 to 900 nm, and multiple broad absorption peaks in the ranges of 1300 to 1700 nm and 1800 to 2100 nm.

[0051] like Figure 3 As shown, it can be seen that the crystal in Example 1 has a strong fluorescence intensity in the range of 1800-3200 nm, for example, a strong fluorescence intensity in the range of 1800-2400 nm and 2700-3200 nm, and particularly a very strong fluorescence intensity in the range of 2700-3200 nm.

[0052] Example 2:

[0053] A holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof are basically the same as those in Example 1, except that the chemical formula of the crystal is 1 at.% Ho, 0.1 at.% Pr: LaYCaSrBaF 12 , lanthanum fluoride and gadolinium fluoride single crystal particles are replaced by lanthanum fluoride and yttrium fluoride (YF3) single crystal particles, and the crystals in Example 2 have similar absorption capacity and fluorescence intensity to those in Example 1.

[0054] Example 3:

[0055] A holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof are basically the same as those in Example 1, except that the chemical formula of the crystal is 1 at.% Ho, 0.1 at.% Pr: LaLuCaSrBaF 12 , the lanthanum fluoride and gadolinium fluoride single crystal particles are replaced by lanthanum fluoride and lutetium fluoride (LuF3) single crystal particles, and the crystals in Example 3 have similar absorption capacity and fluorescence intensity as those in Example 1.

[0056] Example 4:

[0057] A holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof are basically the same as those in Example 1, except that the chemical formula of the crystal is 1 at.% Ho, 0.1 at.% Pr: YLuCaSrBaF 12 , the lanthanum fluoride and gadolinium fluoride single crystal particles are replaced by yttrium fluoride and lutetium fluoride single crystal particles, and the crystals in Example 4 have similar absorption capacity and fluorescence intensity as those in Example 1.

[0058] Example 5:

[0059] A holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof are basically the same as those in Example 1, except that the chemical formula of the crystal is 1 at.% Ho, 0.1 at.% Pr: YGdCaSrBaF 12 , the lanthanum fluoride and gadolinium fluoride single crystal particles are replaced by yttrium fluoride and gadolinium fluoride single crystal particles, and the crystals in Example 5 have similar absorption capacity and fluorescence intensity as those in Example 1.

[0060] Example 6:

[0061] A holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof are basically the same as those in Example 1, except that the chemical formula of the crystal is 1 at.% Ho, 0.1 at.% Pr: LaScCaSrBaF 12 , the lanthanum fluoride and gadolinium fluoride single crystal particles are replaced by lanthanum fluoride and scandium fluoride (ScF3) single crystal particles, and the crystals in Example 6 have similar absorption capacity and fluorescence intensity to those in Example 1.

[0062] Example 7:

[0063] A holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof are basically the same as those in Example 1, except that the chemical formula of the crystal is 1 at.% Ho, 0.1 at.% Pr: YScCaSrBaF 12 , the lanthanum fluoride and gadolinium fluoride single crystal particles are replaced by yttrium fluoride and scandium fluoride single crystal particles, and the crystals in Example 7 have similar absorption capacity and fluorescence intensity to those in Example 1.

[0064] Example 8:

[0065] A holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof are basically the same as those in Example 1, except that the chemical formula of the crystal is 1 at.% Ho, 0.1 at.% Pr:GaScCaSrBaF 12 , the lanthanum fluoride and gadolinium fluoride single crystal particles are replaced by gallium fluoride (GaF3) and scandium fluoride single crystal particles, and the crystals in Example 8 have similar absorption capacity and fluorescence intensity to those in Example 1.

[0066] Example 9:

[0067] A holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof are basically the same as those in Example 1, except that the chemical formula of the crystal is 1 at.% Ho, 0.1 at.% Pr: LaAlCaSrBaF 12 , the lanthanum fluoride and gadolinium fluoride single crystal particles are replaced by lanthanum fluoride and aluminum fluoride (AlF3) single crystal particles, and the crystals in Example 9 have similar absorption capacity and fluorescence intensity to those in Example 1.

[0068] Comparative Example:

[0069] A praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal and a preparation method thereof are substantially the same as those in Example 1, except that the chemical formula of the crystal is 1 at.% Pr:LaGdCaSrBaF 12 The metal raw material of the crystal does not include the holmium fluoride single crystal particles. The Pr 3+ The main application band of is in the visible light range, and it lacks the ability to realize luminescence and laser operation in the infrared band as an activated ion alone. In the embodiment, the crystal is 3+ Activating ions and relative Ho 3+ Low concentration Pr 3+ Co-doping of deactivation ions can effectively make up for this shortcoming.

[0070] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal, characterized in that: The chemical formula of the crystal is Ho,Pr:Me1Me2CaSrBaF 12 , wherein the doping concentration of holmium is 0.5-1.5at.%, the doping concentration of praseodymium is 0.05-0.15at.%, and Me1 and Me2 are respectively selected from one of lanthanum, yttrium, gadolinium, scandium, lutetium, aluminum, and gallium.

2. A method for preparing the holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal according to claim 1, characterized in that: The method comprises the following steps: S1. Grind and mix the various metal raw materials of the crystal; S2, vacuuming, heating and melting the raw materials; S3. Slowly cool the crystal to grow, then quickly cool it to obtain a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal.

3. The method for preparing a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal according to claim 2, characterized in that: In step S1, the holmium raw material of the crystal is holmium fluoride, the praseodymium raw material is praseodymium fluoride, the strontium raw material is strontium fluoride, the calcium raw material is calcium fluoride, the barium raw material is barium fluoride, and the raw materials of Me1 and Me2 are fluoride salts of Me1 and Me2 respectively.

4. The method for preparing a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal according to claim 2, characterized in that: In step S1, a water oxygen remover is added before grinding.

5. The method for preparing a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal according to claim 4, characterized in that: In step S1, the water-oxygen remover is lead fluoride, and the mass fraction of the water-oxygen remover relative to the total mass of the metal raw materials of the crystal is 0.5-1.5 wt.%.

6. The method for preparing a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal according to claim 2, characterized in that: The vacuum degree of the vacuum pump in step S2 is 1×10 -2 Below Pa.

7. The method for preparing a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal according to claim 6, characterized in that: In step S2, the vacuum is firstly drawn to a low vacuum of 5-15 Pa using a mechanical pump, and then the vacuum is drawn to 1×10 -5 ~1×10 -3 Pa of high vacuum.

8. The method for preparing a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal according to claim 2, characterized in that: The heating rate of the temperature in step S2 is 400-500° C. / h, the target temperature is 1400-1500° C., and the constant temperature time is 10-20 h.

9. The method for preparing a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal according to claim 2, characterized in that: The cooling rate of the slow cooling in step S3 is 0.5-2°C / h, and the target temperature is 1000-1100°C.

10. The method for preparing a holmium-praseodymium-doped disordered high-entropy fluoride mid-infrared laser crystal according to claim 2, characterized in that: The cooling rate of the fast cooling in step S3 is 20-40°C / h, and the target temperature is 20-60°C.

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