A method for preparing cobalt-doped anhydrous zinc spinel single crystals under high temperature and high pressure

Abstract

The application discloses a preparation method of a cobalt-doped anhydrous zinc spinel monocrystal under high temperature and high pressure, and comprises the following steps: preparing a zinc spinel powder sample mixture by taking solid basic zinc carbonate powder, solid aluminum isopropyl alcohol powder, solid oxalic acid powder, solid cobalt acetylacetone crystal and liquid dilute nitric acid as starting raw materials; cold-pressing the zinc spinel powder sample mixture into sample round sheets, stacking the sample round sheets vertically together, and placing the sample round sheets in a graphite crucible to be calcined by a high-temperature oxygen atmosphere furnace; obtaining a glassy zinc spinel sample powder after quenching; cold-pressing the glassy zinc spinel sample powder into a cylindrical sample; sealing the cylindrical sample by graphite and then placing the cylindrical sample into a high-temperature high-pressure equipment to perform a high-temperature high-pressure reaction; and finally obtaining the cobalt-doped anhydrous zinc spinel monocrystal. The application breaks through the technical bottleneck of the existing zinc spinel monocrystal synthesis.

Description

Technical Field

[0001] This invention belongs to the technical field of mineral single crystal sample synthesis, and particularly relates to a method for preparing cobalt-doped anhydrous zinc spinel single crystals under high temperature and high pressure. Background Technology

[0002] Zinc spinel, an important end-member component of the spinel subgroup of spinel group minerals, has the chemical formula ZnAl2O4 and is an important oxide mineral rich in both zinc and aluminum. The mineralogical oxide chemical composition percentage of zinc spinel can be expressed as: ZnO / (ZnO+Al2O3) = 44.4% and Al2O3 / (ZnO+Al2O3) = 55.6%. Typically, zinc spinel is a relatively typical normal spinel-type oxide mineral in nature. In the corresponding unit cell, the cubic close-packed proportion of zinc spinel with an anti-spinel structure is only ~0.03, exhibiting obvious normal spinel-type physical characteristics. In nature, zinc spinel crystals have been found to be pale to dark blue and green, or deep blue-green to grayish-green in color. The fracture is conchoidal, without obvious cleavage, and has a gray streak, but possesses a certain vitreous luster, often exhibiting octahedral or rhombic dodecahedral crystal forms. In the field of materials science research, zinc spinel crystals are also an important cathode-emitting semiconductor material with a wide band gap energy reaching 3.9 electron volts; its absorption wavelength range in the ultraviolet region is also long, reaching up to 320 nanometers. Therefore, it has extremely broad application prospects in the research and development of ultraviolet light devices and new semiconductor materials. Geological data from identified fields have confirmed the presence of zinc spinel mineral crystals with a color similar to sapphire in Brazil, Portugal, Nigeria, Sri Lanka, and other locations. Moreover, these zinc spinel crystals are mostly found in skarn deposits at the contact zone between intermediate-acidic to intermediate-basic intrusive rocks and carbonate rocks.

[0003] In the zinc spinel crystal structure, the transition metal cobalt readily occupies tetrahedral positions, leading to isomorphic substitution of A-site divalent cations. Since the substituted zinc and the doped cobalt in zinc spinel have the same +2 valence, this isomorphic substitution is considered equivalent isomorphic substitution. Cobalt (Co) is located in period 4 and group VIII of the periodic table, with atomic number 27 and a 3d electron configuration. 7 4s 2Cobalt is a silvery-white ferromagnetic metal, with common compound valence states including -1, 0, +1, +2 (primarily), +3 (primarily), +4, and +5. In the Earth's crust, the average mass percentage of cobalt is only 0.001%; ​​while in the ocean, the total amount of cobalt is approximately 2.3 billion tons. There are hundreds of cobalt-containing minerals in nature, but to date, geologists have not discovered any cobalt minerals that can form minerals on their own. Typically, in cobalt-containing metal sulfide deposits, cobalt is associated with numerous other metals such as zinc, copper, nickel, lead, iron, silver, and manganese. Due to its widespread application in many high-tech industries worldwide, including lithium-ion batteries for new energy vehicles, aero engines, high-temperature hard alloys, ceramic metallurgy, pigment catalysis, quenching materials, and cobalt-based magnetic materials, cobalt minerals are recognized globally as an important and critical mineral resource. In addition, cobalt is also one of the trace elements required by the human body. Researchers have recently isolated a red crystal from liver concentrate containing approximately 4.5% cobalt, also known as cobalamin, or vitamin B12. Generally, geologists classify key cobalt mineral resources into isolated cobalt deposits and dispersed cobalt deposits based on factors such as the industrial grade of the ore, the thickness of the ore body, and the enrichment state of the element. Isolated cobalt deposits are further divided into three categories: cobalt arsenide deposits, cobalt sulfide deposits, and cobalt ore deposits. Dispersed cobalt deposits refer to ores in which a large amount of cobalt is dispersed in skarn-type iron ore, hydrothermal polymetallic ore, vanadium-titanium magnetite, sedimentary cobalt-manganese ore, copper-nickel sulfide ore, and nickel silicate ore. Although the industrial grade of the transition metal cobalt in these dispersed cobalt deposits is not high, the ore bodies containing cobalt resources are usually large in scale, making them an important source of strategic key minerals for industrial extraction of cobalt.

[0004] As a typical nominally anhydrous mineral, zinc spinel does not contain water molecules or hydroxyl groups in its molecular structure. It is a relatively common oxide-group high-pressure mineral found in the deep lower crust and upper mantle regions of the Earth. Existing laboratory high-temperature and high-pressure experimental simulations and theoretical calculations of mineral physics simulations show that the anomalous electrical properties and elastic wave propagation velocities widely present in the mantle transition zone at depths from 410 km to 660 km, corresponding to pressures and temperatures of 16.0-23.0 GPa and 1450-1800℃, are caused by the mineral phase transformation between spinel and post-spinel. Looking at the methods used in the artificial synthesis of zinc spinel in laboratory materials science both domestically and internationally, the main methods include: microemulsion method, high-temperature solid-state sintering method, high-pressure hydrothermal synthesis method, inorganic salt sol-gel method, and ammonia chemical co-precipitation method. Since most of these existing synthesis techniques involve simple solution chemical reactions or direct particle physical grinding of sample powder followed by high-temperature sintering, they are more suitable for preparing nano-sized zinc spinel crystals. In high-temperature and high-pressure experimental geoscience research, single-crystal mineral samples with micron-sized or larger particles are typically required. Clearly, nanoscale zinc spinel samples synthesized in previous studies have failed to meet the minimum particle size requirements, and no effective synthesis method has yet been found. Previously, many geoscientists have used natural zinc spinel samples instead of artificially synthesized samples to meet the needs of high-temperature and high-pressure experimental geoscience research. However, these natural samples suffer from significant drawbacks due to the uneven distribution of the trace element cobalt. Therefore, effectively synthesizing a large-particle cobalt-doped anhydrous zinc spinel single crystal that meets the needs of various high-temperature and high-pressure laboratory simulations in geoscience research, especially for studying the optimal lattice orientation and crystal axis anisotropy of zinc spinel single crystals under high pressure, has become particularly urgent. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing cobalt-doped anhydrous zinc spinel single crystals under high temperature and high pressure, so as to fill the technical gap in the preparation of large-particle cobalt-doped anhydrous zinc spinel single crystals under high temperature and high pressure conditions, and to obtain experimental samples of large-particle cobalt-doped anhydrous zinc spinel single crystals.

[0006] The technical solution of this invention is:

[0007] A method for preparing cobalt-doped anhydrous zinc spinel single crystals under high temperature and high pressure, the method comprising: preparing a zinc spinel powder sample mixture using solid basic zinc carbonate powder, solid aluminum isopropoxide powder, solid oxalic acid powder, solid cobalt acetylacetone crystals, and liquid dilute nitric acid as starting materials; cold pressing the zinc spinel powder sample mixture into sample discs, stacking the sample discs vertically together and placing them in a graphite crucible for calcination in a high-temperature oxygen atmosphere furnace, and quenching to obtain glassy zinc spinel sample powder; cold pressing the glassy zinc spinel sample powder into cylindrical samples, sealing the cylindrical samples with graphite and placing them in a high-temperature and high-pressure device for high-temperature and high-pressure reaction, finally obtaining cobalt-doped anhydrous zinc spinel single crystals.

[0008] Solid basic zinc carbonate powder with a purity >99.99%, solid aluminum isopropoxide powder with a purity >99.99%, solid oxalic acid powder with a purity >99.99%, solid cobalt acetylacetone crystals with a purity >99.99%, and liquid dilute nitric acid with a concentration of 10%.

[0009] The preparation method of zinc spinel powder sample mixture includes:

[0010] Step 1: Weigh out 60 ml of 10% dilute nitric acid and place it in a 500 ml notched beaker;

[0011] Step 2: Weigh out 5.0 grams of basic zinc carbonate powder and add it to a notched beaker. Place a magnetic stirring rotor into the notched beaker.

[0012] Step 3: Cover the notched beaker with a glass watch glass.

[0013] Step 4: Weigh out 17.9079 g of solid aluminum isopropoxide powder and 80 mg of solid cobalt acetylacetone crystals according to the stoichiometric ratio of zinc spinel (Zn,Co)Al2O4, and add them separately to a dilute nitric acid solution containing basic zinc carbonate.

[0014] Step 5: Cover the notched beaker with a glass watch glass.

[0015] Step 6: Place the notched beaker on a high-temperature magnetic stirring plate in a fume hood and stir at 800 rpm for 48 hours at room temperature.

[0016] Step 7: Weigh out 2 grams of solid oxalic acid powder and place it into a notched beaker;

[0017] Step 8: After covering with a glass petri dish, stir for 36 hours at 80°C and 1000 rpm on a high-temperature magnetic stirring hot plate.

[0018] Step 9: Remove the glass watch glass from the beaker, and increase the temperature of the high-temperature magnetic stirring plate to 110°C until the mixed solution in the entire notched beaker is completely evaporated.

[0019] Step 10: Remove all the mixed powder from the notched beaker and place it in a graphite crucible;

[0020] Step 11: Place the graphite crucible containing the mixed powder into a muffle furnace, raise the temperature to 1100℃ at a heating rate of 300℃ / hour, and hold the temperature for 5 hours.

[0021] Step 12: After cooling the mixture powder in the muffle furnace to room temperature at a cooling rate of 200℃ / hour, remove the mixture sample powder;

[0022] Step 13: Place the sample powder in a corundum mortar and grind for 1 hour to obtain a zinc spinel powder sample mixture.

[0023] Methods for cold-pressing zinc spinel powder sample mixtures into sample discs include:

[0024] Step 14: The zinc spinel powder sample mixture is cold-pressed into a Φ10.0mm×3.0mm sample disc using a tungsten carbide mold of a stainless steel tablet press.

[0025] Methods for obtaining glassy zinc spinel sample powder by vertically stacking sample discs together, placing them in a graphite crucible, calcining them in a high-temperature oxygen atmosphere furnace, and then quenching them include:

[0026] Step 15: Place the three sample discs vertically stacked inside the graphite crucible wall and suspend the graphite crucible in the center of the high-temperature oxygen atmosphere furnace; fix the two ends of the platinum-rhodium metal wire connecting the graphite crucible to the vertical four-hole alumina tube, and fix the upper end of the four-hole alumina tube to the center of the round cover that can be put into or pulled out of the furnace body at any time.

[0027] Step 16: Place a stainless steel container filled with deionized pure cold water on the side of the high-temperature oxygen atmosphere furnace.

[0028] Step 17: Connect the top of the high-temperature oxygen atmosphere furnace to an argon inert gas cylinder and a carbon monoxide and carbon dioxide cylinder with adjustable ratios.

[0029] Step 18: Open the argon inert gas valve and continue to purge for 30 minutes; under the protection of argon inert gas, heat the high-temperature oxygen atmosphere furnace to 800℃ at a heating rate of 400℃ / hour.

[0030] Step 19: After the temperature inside the furnace reaches 800℃, switch the carbon monoxide and carbon dioxide gas control valves to make the volume ratio of carbon monoxide and carbon dioxide passing through the sample oxygen atmosphere furnace reach 4:1.

[0031] Step 20: Increase the temperature of the sample chamber inside the furnace to 1400℃ at a heating rate of 200℃ / hour, and bake at a constant temperature for 15 minutes.

[0032] Step 21: Pull the graphite crucible containing the sample, the four-hole alumina tube, and the round cover on the furnace body out of the furnace body together, and immerse them directly in secondary deionized pure water for quenching into glassy zinc spinel.

[0033] Step 22: Take the quenched glassy zinc spinel out of the graphite crucible, put it into a corundum mortar and grind it into powder. Place the glassy zinc spinel powder in a vacuum drying oven at 200°C and dry it for 12 hours to obtain glassy zinc spinel sample powder.

[0034] The method for obtaining cobalt-doped anhydrous zinc spinel single crystals by cold-pressing glassy zinc spinel sample powder into cylindrical samples, sealing the cylindrical samples with graphite, and then placing them in a high-temperature and high-pressure equipment for a high-temperature and high-pressure reaction includes:

[0035] Step 23: The glassy zinc spinel powder is cold-pressed on a cold isostatic press using a tungsten carbide mold with a diameter of 4.0 mm and a diameter of 10.0 mm to obtain a cylindrical sample with a diameter of 4.0 mm and a diameter of 4.0 mm.

[0036] Step 24: Seal the cylindrical sample inside a graphite tube with an inner diameter of 4.0 mm × 4.4 mm and a wall thickness of 0.2 mm. Seal the upper and lower ends of the graphite tube with graphite sheets.

[0037] Step 25: Place the sealed graphite tube on a typical 6-8 type multi-faceted top large cavity high temperature and high pressure equipment of Kawai-1000t in the laboratory. Set the pressure increase rate and the temperature increase rate to 0.5 GPa / hour and 10℃ / minute, respectively. Under the conditions of raising the pressure and temperature to 3.0 GPa and 1050℃, respectively, hot pressing sintering is carried out. The reaction time is 72 hours of constant temperature and pressure.

[0038] Step 26: After maintaining constant temperature and pressure for 72 hours, the temperature inside the sample chamber is reduced from 1050℃ to 800℃ at a cooling rate of 3℃ / min, and held at that temperature for 1 hour; then the temperature inside the sample chamber is reduced from 800℃ to room temperature at a cooling rate of 5℃ / min.

[0039] Step 27: After the temperature inside the sample chamber drops to room temperature, reduce the pressure inside the sample chamber from 3.0 GPa to atmospheric pressure at a depressurization rate of 0.5 GPa / hour.

[0040] Step 28: After the high-temperature and high-pressure reaction is completed, the graphite tube is removed from the typical 6–8 type multi-faceted top large cavity high-temperature and high-pressure equipment of Kawai-1000t; after removing the graphite tube that encapsulates the sample, cobalt-doped anhydrous zinc spinel single crystal is obtained.

[0041] During the high-temperature and high-pressure reaction, the temperature was calibrated using two sets of high-temperature resistant tungsten-rhenium thermocouples. Each set of tungsten-rhenium thermocouples was composed of two different tungsten-rhenium alloys with the chemical composition W... 95％ Re 5％ and W 74％ Re 26％ Each set of tungsten-rhenium thermocouples is symmetrically placed at the upper and lower ends of the graphite tube sample chamber.

[0042] The beneficial effects of this invention are:

[0043] This invention organically combines the backgrounds of mineral processing, mining geology, ore field structural geology, economic geology, gemology, field experimental petrology, trace element geochemistry, mineralogy, crystallography, mineralogy, dispersed element geochemistry, magmatic petrology, sedimentary petrology, metamorphic petrology, high-pressure mineral physics, crystal optics, optical mineralogy, and nanogeochemistry, etc. It employs a typical 6–8 type multi-faceted top large-cavity high-temperature and high-pressure laboratory Kawai-1000t equipment to simulate the formation process of cobalt-doped anhydrous zinc spinel single crystals under high-temperature and high-pressure conditions. The main chemical reaction equations involved in this invention are:

[0044] [ZnCO3·2Zn(OH)2·H2O]+6HNO3→3Zn(NO3)2+CO2+6H2O

[0045] Zn(NO3)2+2C9H 21 AlO3→ZnAl2O4+2(NH3·H2O)+6C2H2+6CO+10H2

[0046] ZnAl2O4+Co(C5H8O2)2→(Zn,Co)Al2O4+3C2H2+2CH4+2CO2+H2

[0047] This invention uses basic zinc carbonate [chemical formula: ZnCO3·2Zn(OH)2·H2O, also known as hydrated zinc ore] as the initial raw material. It is a white, fine, amorphous solid powder with stable chemical properties, odorless and tasteless, insoluble in water and ethanol, but readily soluble in dilute acids and sodium hydroxide. It is mainly used in the preparation and production of latex products, light astringents, rayon, skin protectants, desulfurizers, etc. Furthermore, it has wide applications in industrial pharmaceuticals and food additives. The amorphous basic zinc carbonate solid powder is chosen because of its stable properties and superior solubility in dilute acids, making it an excellent raw material for providing zinc in artificially synthesized zinc spinel. The initial raw material is aluminum isopropoxide [chemical formula: C9H...] 21AlO3 is a white, tetrameric, powdery solid substance with strong hygroscopic properties and high chemical reactivity; it decomposes easily in water. Aluminum isopropoxide powder is chosen because its easy decomposition in dilute acid solutions and strong chemical reactivity make it an excellent raw material for providing aluminum in synthetic zinc spinel. The initial raw material, cobalt acetylacetonate [chemical formula: Co(C5H8O2)2, also known as cobalt acetylacetonate(II)], is a white monoclinic crystalline solid existing as a tetramer. In this invention, white cobalt acetylacetonate crystals are chosen because they dissolve in dilute nitric acid solution, making them an excellent raw material for providing the trace element cobalt in synthetic zinc spinel. The chemical reaction products involved in this invention, including NH3·H2O, CH4, C2H2, CO2, CO, and H2, are all highly volatile substances at high temperatures.

[0048] This invention aims to synthesize large-particle single crystals of anhydrous zinc spinel with high cobalt content. The synthesized samples contain cobalt-doped zinc spinel single crystals that are compatible with the development and comprehensive utilization of zinc mineral resources. These crystals are then widely applied in diagenetic and mineralization simulation studies of the physicochemical properties of minerals and rocks under high temperature and high pressure conditions. Compared to naturally exposed zinc spinel samples, which may contain impurities such as magnesium, manganese, and chromium ions, the preparation process of the cobalt-doped anhydrous zinc spinel single crystals in this invention utilizes a pure laboratory environment. The samples are kept in a sealed environment, preventing contact with impurities. The resulting cobalt-doped anhydrous zinc spinel single crystals are pure and chemically stable, providing crucial experimental sample support for measuring the physical properties of cobalt-doped anhydrous zinc spinel single crystals, especially for investigating the anisotropy of crystal axes and the optimal lattice orientation of spinel single crystals under high pressure.

[0049] Compared to previously known synthetic zinc spinel single crystals, which employed methods such as microemulsion synthesis, high-temperature solid-state sintering, high-pressure hydrothermal synthesis, inorganic salt sol-gel synthesis, and ammonia chemical co-precipitation, the preparation method of this invention offers significant advantages, including simple operation and short reaction time. The resulting zinc spinel single crystals exhibit superior physicochemical properties, including high purity, large size, and stable chemical performance. Crucially, the synthesized zinc spinel product has a high cobalt content (6000-8000 ppm wt%), and this cobalt content is entirely controllable. The large particle size of zinc spinel single crystals fully meets the sample requirements for high-temperature and high-pressure experiments on diamond pressure chambers, including conductivity, synchrotron X-ray diffraction, confocal Raman spectroscopy, and vacuum Fourier transform infrared spectroscopy. This method provides important experimental sample support for measuring the physical properties of cobalt-doped anhydrous zinc spinel single crystals, especially for exploring the optimal orientation of the single crystal lattice and the anisotropy of the crystal axis under high pressure, thus breaking through the technical bottleneck of existing zinc spinel single crystal synthesis. Detailed Implementation

[0050] A method for preparing cobalt-doped anhydrous zinc spinel single crystals under high temperature and high pressure, comprising:

[0051] This invention uses solid, white, fine, amorphous basic zinc carbonate powder (purity: >99.99%), solid aluminum isopropoxide powder (purity: >99.99%), solid oxalic acid powder (purity: >99.99%), solid cobalt acetylacetone crystals (purity: >99.99%), and liquid dilute nitric acid (concentration: 10%) as starting materials.

[0052] The initial material used in this invention is high-purity solid basic zinc carbonate, a white, fine, amorphous solid powder. It is chemically stable, odorless, tasteless, insoluble in water and ethanol, but readily soluble in dilute acids and sodium hydroxide. It is mainly used in the preparation and production of latex products, light astringents, rayon, skin protectants, desulfurizers, etc. Furthermore, it has wide applications in industrial pharmaceuticals and food additives. The amorphous solid basic zinc carbonate powder is chosen because of its stable properties and superior solubility in dilute acids, making it an excellent raw material for providing zinc in synthetic zinc spinel.

[0053] The high-purity solid aluminum isopropoxide powder selected for this invention is a white, tetramer-like substance with strong hygroscopic properties and high chemical reactivity, readily decomposing upon contact with water. Aluminum isopropoxide powder was chosen because of its superior characteristics of easy decomposition in dilute acid solutions and high chemical reactivity, making it an excellent raw material for providing aluminum in the artificial synthesis of zinc spinel.

[0054] The high-purity cobalt acetylacetonate selected as the initial material in this invention is a white monoclinic crystal existing as a tetramer. This invention selects white cobalt acetylacetonate crystals because they are soluble in dilute nitric acid solution, making them an excellent raw material for providing trace element cobalt in artificially synthesized zinc spinel.

[0055] The high-purity solid oxalic acid selected as the initial material in this invention is a chelating agent for metal substances. Its purpose is that oxalic acid powder has a significant impact on the bioavailability of minerals and has a very strong chelating effect. When oxalic acid combines with divalent zinc ions, it can greatly reduce their solubility, thereby forming a complex sol of divalent zinc ions in dilute nitric acid solution. At the same time, when oxalic acid combines with the transition metal cation cobalt, due to its chelating effect, a complex of soluble transition metal cations is formed. The solubility of the divalent cobalt metal cation in acid solution will be significantly enhanced, allowing it to fully dissolve in dilute nitric acid solution.

[0056] The dilute nitric acid (concentration: 10%) used as the initial material in this invention may cause residues of basic zinc carbonate, aluminum isopropoxide, cobalt acetylacetonate, and oxalic acid powder if the nitric acid concentration is too low due to its limited solubility. If the nitric acid concentration is too high, its oxidizing properties will be enhanced, causing the basic zinc carbonate in the sample to undergo a rapid oxidation reaction or decompose directly, producing dense fumes, which may pose certain dangers to the preparation process.

[0057] The specific steps of this invention include:

[0058] Step 1: Open the chemical fume hood, select a standard 100 ml volumetric flask, accurately weigh out 60 ml of 10% dilute nitric acid, place a glass pipette in a 500 ml notched beaker, and carefully transfer all the liquid dilute nitric acid into the beaker along the pipette. The notched beaker is chosen as the reaction vessel mainly because it is not completely sealed after the glass watch glass is covered, and the generated gas can easily evaporate in the fume hood.

[0059] Step 2: On a 10-microgram high-precision analytical balance, accurately weigh out 5.0 grams of high-purity white fine amorphous basic zinc carbonate powder, carefully add it to a notched beaker containing a 10% concentration of dilute nitric acid solution, and place a magnetic stirring rotor inside.

[0060] Step 3: Using a glass petri dish, cover the notched mouth of the beaker containing the dilute nitric acid solution of solid basic zinc carbonate powder and place it on a high-temperature magnetic stirring plate in a fume hood. In order to fully dissolve the initial material, solid basic zinc carbonate powder, in the dilute nitric acid solution, and at the same time allow it to undergo hydrolysis and acidification reactions, the reaction conditions are room temperature, 700 rpm, and 72 hours.

[0061] Step 4: According to the stoichiometric ratio of zinc spinel (Zn,Co)Al2O4, accurately weigh 17.9079 grams of high-purity solid aluminum isopropoxide powder and 80 milligrams of high-purity solid cobalt acetylacetone crystals on a high-precision analytical balance, and carefully add them separately to a dilute nitric acid solution containing basic zinc carbonate.

[0062] Step 5: Place the dilute nitric acid solution containing solid basic zinc carbonate powder, solid aluminum isopropoxide powder, and solid cobalt acetylacetone crystals into a beaker, cover it with a glass watch glass to ensure that the gas generated by the reaction evaporates through the beaker's notch, and to prevent the dilute nitric acid solution of the initial materials from splashing out during high-speed stirring, which could cause danger and affect the accuracy of zinc spinel synthesis.

[0063] Step 6: Place the sealed initial dilute nitric acid mixture and the magnetic stirring rotor on a high-temperature magnetic stirring plate in a fume hood. Under the conditions of room temperature, a speed of 800 rpm, and a stirring time of 48 hours, the initial solid cobalt acetylacetone crystals are completely dissolved in the dilute nitric acid mixture without any residue. At the same time, volatile substances such as NH3·H2O, CH4, C2H2, CO2, CO, and H2 are more easily volatilized in the fume hood.

[0064] Step 7: Accurately weigh 2 grams of high-purity solid oxalic acid powder on a high-precision analytical balance. Add the high-purity oxalic acid powder, which is an important metal chelating agent, to a dilute nitric acid solution containing solid basic zinc carbonate powder, solid aluminum isopropoxide powder, and solid cobalt acetylacetone crystals. The purpose is that oxalic acid powder has a significant impact on the bioavailability of minerals and has a very strong chelating effect. When oxalic acid combines with divalent zinc ions, it can greatly reduce their solubility, thereby forming a complex sol of divalent zinc ions in the dilute nitric acid solution. At the same time, when oxalic acid combines with the transition metal divalent cation cobalt, due to its chelating effect, a soluble transition metal divalent cation cobalt complex is formed. The solubility of the divalent cobalt metal cation in the acid solution will be significantly enhanced, allowing it to fully dissolve in the dilute nitric acid solution.

[0065] Step 8: Place the notched beaker of the mixture back on the high-temperature magnetic stirring plate in the fume hood, cover it with a glass watch glass, and set the conditions of the high-temperature magnetic stirring plate to 80°C, 1000 rpm and stirring time for 36 hours, so that all the initial reagents form a uniform sol under the combined action of the mixed solution of dilute nitric acid and oxalic acid.

[0066] Step 9: Remove the glass watch glass from the beaker, and increase the temperature of the high-temperature magnetic stirring plate to 110°C until the mixed solution in the entire notched beaker is completely evaporated.

[0067] Step 10: Remove the magnetic stirring rotor from the notched beaker on the high-temperature magnetic stirring plate and clean all the powder sample adhering to its surface into the beaker. Carefully remove all the mixed powder from the notched beaker with a spatula and place it in a graphite crucible. The purpose of using a graphite crucible is that the carbon that makes up the graphite crucible inevitably produces a certain concentration of carbon monoxide and carbon dioxide during the high-temperature calcination process, thereby controlling the oxygen fugacity inside the zinc spinel graphite crucible and ultimately constraining the valence state of the variable-valence metal cation cobalt in the zinc spinel sample.

[0068] Step 11: Place the graphite crucible containing the mixed powder into a muffle furnace under normal pressure and high temperature conditions, raise the temperature to 1100℃ at a relatively slow heating rate of 300℃ / hour, and hold at that temperature for 5 hours. The relatively slow high-temperature calcination rate and the longer holding time are intended to better control the oxygen atmosphere within the graphite sample chamber, and to better remove residual nitric acid, oxalic acid, and other organic matter from the mixed powder.

[0069] Step 12: Cool the mixed sample powder in the graphite crucible in the muffle furnace to room temperature at a cooling rate of 200℃ / hour. Compared with the heating rate, choosing a slower cooling rate makes it easier to form a honeycomb-like loose sample powder. Carefully remove the mixed sample powder.

[0070] Step 13: Place the loose, honeycomb-like sample powder in an ultra-hard, thickened corundum mortar and grind it thoroughly for 1 hour to obtain a fine-grained and homogenized zinc spinel powder sample mixture.

[0071] Step 14: The uniform and fine-grained zinc spinel powder sample mixture is cold-pressed into three sample discs of Φ10.0mm×3.0mm using a high-precision tungsten carbide mold of a stainless steel tablet press with dimensions of Φ10.0mm×10.0mm. The three cold-pressed sample mixture discs are then stacked vertically together and placed in a graphite crucible.

[0072] Step 15: On the wall of the graphite crucible containing three stacked samples, drill two symmetrical circular holes with a diameter of 1.0 mm using a high-speed electric drill. Carefully thread a 0.5 mm platinum-rhodium alloy wire through the two symmetrical circular holes in the graphite crucible wall, suspending it in the center of the high-temperature oxygen atmosphere furnace. Fix the two ends of the platinum-rhodium wire connecting the graphite crucible to a vertical four-hole alumina tube with a diameter of 0.6 mm. The four-hole alumina tube has an outer diameter of 5.0 mm and a length of 40 cm. The upper end of the four-hole alumina tube is fixed in the center of a circular lid that allows for easy insertion and removal of the furnace body.

[0073] Step 16: Place a 3-liter stainless steel container filled with deionized purified cold water on the side of the high-temperature oxygen atmosphere furnace. The purpose is to allow the graphite crucible containing the sample to be pulled directly out of the high-temperature oxygen atmosphere furnace at extremely high temperatures and quickly immersed in the 3-liter stainless steel container of deionized water for rapid cooling. The main purpose is to prevent the cobalt element, which is a variable valence metal, from being oxidized / reduced again during the slow cooling of the furnace, thus achieving rapid quenching of the sample and completely preserving the glassy state of the zinc spinel sample.

[0074] Step 17: At the very top of the high-temperature oxygen atmosphere furnace, it is interconnected with argon inert gas cylinders and adjustable proportions of carbon monoxide and carbon dioxide cylinders. The amount of gas introduced into the sample chamber is controlled by a pressure gauge. During the high-temperature calcination of the sample, each gas can be switched and adjusted at any time via valves. This invention uses argon inert gas to provide an absolutely reducing oxygen atmosphere environment when the furnace temperature is below 800°C.

[0075] This invention employs a precisely proportioned mixture of carbon monoxide and carbon dioxide to effectively control oxygen fugacity during high-temperature calcination of samples when the furnace temperature exceeds 800°C. If argon inert gas is continuously introduced when the furnace temperature exceeds 800°C, it will result in an over-reducing oxygen atmosphere within the sample chamber, potentially reducing the variable-valence element cobalt to metallic cobalt. Therefore, at temperatures above 800°C, we use a precisely proportioned mixture of carbon monoxide and carbon dioxide to control the oxygen fugacity of the sample within the high-temperature oxygen atmosphere furnace chamber. The reaction principle is as follows: It can effectively adjust the partial pressure of oxygen in the sample chamber, thereby realizing the valence state of cobalt, a variable-valence metal element, in cobalt-doped anhydrous zinc spinel single crystals.

[0076] The maximum rated temperature of the high-temperature oxygen atmosphere furnace body is 1800℃. Turn on the circulating cooling water of the high-temperature oxygen atmosphere furnace to reduce the temperature of the furnace body, preventing the overall furnace body temperature from becoming too high, which could cause carbon monoxide and carbon dioxide leaks and thus pose a danger.

[0077] Activate the highly sensitive monitoring alarms for argon, carbon monoxide, and carbon dioxide concentrations to prevent gas leaks during the high-temperature calcination process in the oxygen atmosphere furnace and ensure operator safety.

[0078] Step 18: Open the argon inert gas valve and rotate the pointer button controlled by the gas pressure gauge to continuously purge the sample chamber for 30 minutes. This is to properly expel excess air from the sample chamber. Under the protection of argon inert gas, calcine the sample to 800℃ at a heating rate of 400℃ / hour.

[0079] Step 19: After the furnace body temperature reaches 800℃, quickly switch the carbon monoxide cylinder and carbon dioxide gas control valve, and rotate the pointer button controlled by the gas pressure gauge to make the volume ratio of carbon monoxide and carbon dioxide in the sample oxygen atmosphere furnace reach 4:1. The purpose is that during the high-temperature calcination process, the mixed gas of carbon monoxide and carbon dioxide with this volume ratio can effectively regulate the oxygen fugacity in the sample chamber.

[0080] Step 20: After the mixed gas flow of carbon monoxide and carbon dioxide (volume ratio 4:1) controlling the oxygen fugacity in the sample chamber reaches stability (this step requires approximately 3–5 minutes), the temperature of the sample chamber inside the furnace is then increased to 1400°C at a heating rate of 200°C / hour, and calcined at this temperature for 15 minutes to melt it into glassy zinc spinel. During the heating process in the high-temperature oxygen atmosphere furnace, two completely different heating rates of 400°C / hour and 200°C / hour were used for the sample chamber in different temperature ranges: from room temperature to 800°C and from 800°C to 1400°C. This invention, by applying a relatively slow heating rate as the temperature of the sample chamber inside the high-temperature oxygen atmosphere furnace rises, will be more conducive to the formation of strong ionic bonds such as Zn–O, Al–O, and Co–O in cobalt-doped zinc spinel; it will achieve more precise temperature control of the sample chamber inside the high-temperature oxygen atmosphere furnace; and it will completely avoid the problem of excessively high local temperatures in the furnace due to unbalanced heat transfer in the sample chamber, which could easily damage the heating element of the oxygen atmosphere furnace, among other objectives.

[0081] The purpose of the high-temperature calcination process using a mixture of carbon monoxide and carbon dioxide to control the oxygen atmosphere is to provide a purer glassy state of zinc spinel for the synthesis of large-particle cobalt-doped anhydrous zinc spinel single crystals in this invention; the high-temperature calcination under oxygen atmosphere conditions can better control the valence state of cobalt, a variable-valence metal element in the product; and the relatively high calcination temperature of 1400℃ can ensure that any small amount of volatiles, nitric acid, oxalic acid, organic matter, and other substances that may remain after high-temperature calcination in the muffle furnace and affect sample preparation have all been completely volatilized.

[0082] This invention employs a constant-temperature calcination of 15 minutes, a relatively short calcination time, because zinc spinel powder melts rapidly at temperatures above 1350℃. If the calcination time is too short, some initial powder residue may remain in the molten zinc spinel, severely affecting the chemical composition of the prepared zinc spinel sample. A short calcination time also hinders sufficient ion exchange and chemical diffusion between zinc, aluminum, and cobalt ions, and impedes the formation of stable chemical bonds in the strong ionic bonds (Zn–O, Al–O, Co–O, etc.) within the zinc spinel. Furthermore, a short calcination time leads to uneven distribution of the doped cobalt element, such as stratification and differentiation, severely impacting the preparation results. A short calcination time also reduces the product density, making it difficult to form highly dense zinc spinel glass. However, a calcination time exceeding 15 minutes may result in excessive melting, causing the sample to adhere firmly to the graphite crucible wall, making cleaning difficult and increasing sample preparation costs.

[0083] Step 21: After the sample has been calcined at a constant temperature of 1400℃ for 15 minutes, the graphite crucible containing the sample, the four-hole alumina tube, and the round cover on the furnace body are pulled out of the furnace body and directly immersed in a stainless steel container containing 3 liters of double-deionized pure cold water to rapidly quench it into zinc spinel glass. The purpose of rapid quenching is to preserve the glassy zinc spinel sample with uniform composition at high temperature.

[0084] Step 22: Carefully remove the quenched glassy zinc spinel sample from the graphite crucible and grind it thoroughly in a corundum mortar to form a fine-grained and homogeneous powder. Place the glassy zinc spinel powder in a vacuum drying oven at 200°C and dry for 12 hours.

[0085] Step 23: On a cold isostatic press, zinc spinel glass powder is cold-pressed into cylindrical samples of Φ4.0mm×4.0mm using a high-precision tungsten carbide mold with a diameter of Φ4.0mm × 10.0mm.

[0086] Step 24: Seal the cylindrical zinc spinel sample inside a graphite tube with an inner diameter of 4.0 mm × 4.4 mm and a wall thickness of 0.2 mm. Use graphite sheets with a diameter of 4.0 mm × 0.2 mm (height) at the top and bottom of the sample tube. The main purpose of using graphite as a sealing material is to control the oxygen fugacity values ​​of carbon monoxide and carbon dioxide within the sample cavity, and ultimately to constrain the valence state of the variable-valence metal element cobalt in the zinc spinel sample.

[0087] Step 25: Zinc spinel is one of the important zinc- and aluminum-rich oxide minerals in the lower crust and upper mantle regions of Earth and other terrestrial planets. To realistically simulate the growth environment of zinc spinel in the lower crust of Earth and other terrestrial planets, and to invert the temperature and pressure conditions for the stable existence of the zinc spinel mineral phase, a graphite tube containing the sample was placed on a typical 6–8 type multi-faceted top large cavity high-temperature and high-pressure equipment of Kawai-1000t in the laboratory. The pressure and temperature were set to 0.5 GPa / hour and 10℃ / minute, respectively. Hot pressing sintering was carried out under the conditions of 3.0 GPa and 1050℃, respectively, and the reaction time was constant temperature and pressure for 72 hours.

[0088] The preparation process using the 3.0 GPa high pressure and 1050℃ sintering temperature selected in this invention is designed entirely based on the physicochemical properties of zinc spinel itself. The main objectives are as follows: First, the high-temperature, high-pressure conditions, relatively slow pressure and temperature increase rates, and long isothermal and isostatic reaction time ensure a complete mineral phase transformation from the initial zinc spinel glass phase powder to the zinc spinel crystalline phase, and the final product, the zinc spinel mineral phase, remains stable under these temperature and pressure conditions. Second, the high-temperature, high-pressure conditions, relatively slow pressure and temperature increase rates, and long isothermal and isostatic reaction time significantly increase the self-diffusion and chemical diffusion coefficients of metal cations such as zinc, aluminum, and cobalt ions, thereby achieving isomorphic substitution of zinc ions by cobalt ions in the zinc spinel crystal, with complete reaction and no residual free cobalt element, thus forming a perfect rare-earth element cobalt-doped zinc spinel single crystal sample. Furthermore, the high-temperature, high-pressure... The preparation process, characterized by specific conditions, a relatively slow rate of pressure and temperature increase, and a long isothermal and isobaric reaction time, ensures the formation of stable chemical bonds between Zn–O, Al–O, and Co–O. This prevents uneven distribution of cobalt elements, such as stratification and differentiation, within the zinc spinel, resulting in a uniform equiaxed cobalt-doped zinc spinel single crystal sample. Furthermore, the high-temperature, high-pressure conditions, relatively slow rate of pressure and temperature increase, and long isothermal and isobaric reaction time lead to a more uniform distribution of cobalt elements in the final zinc spinel product. This also increases the product's density, strength, and particle size, resulting in a large-particle equiaxed cobalt-doped zinc spinel single crystal sample with superior physicochemical properties, including uniform elemental distribution, high mechanical strength, and high density.

[0089] In this invention, during the high-temperature and high-pressure reaction, the temperature is precisely calibrated using two sets of high-temperature resistant tungsten-rhenium thermocouples. Tungsten-rhenium thermocouples have advantages such as good temperature-potential linearity, reliable thermal stability, and low cost, enabling temperature calibration within a range of 0-2300℃. They are widely used in ultra-high-temperature temperature calibration in fields such as high-pressure mineral physics experiments, advanced metallurgical industries, high-temperature electronic thermoelectric system structural engineering, space vehicles, and nuclear reactors. Each set of tungsten-rhenium thermocouples is composed of two different tungsten-rhenium alloys with the following chemical composition: W... 95％ Re 5％ and W 74％ Re 26％Tungsten-rhenium thermocouple wires of different materials, each with a diameter of 0.1 mm, were joined together at one end and twisted into a spiral shape using a vise. The other ends of the wires were connected to the positive and negative terminals of a high-power welding regulated DC power supply. The output current control knob of the power supply was adjusted to apply a large current to the wires, completely immersing the twisted tungsten-rhenium thermocouple wires in a saturated sodium chloride solution. The wires were melted and welded into spheres, and the oxide layer on the spherical thermocouple wires was removed. Using the same technique, two sets of tungsten-rhenium thermocouples were prepared, and each set was symmetrically placed at the upper and lower ends of the graphite tube sample chamber. This invention employs a dual thermocouple consisting of tungsten and rhenium placed at both the top and bottom ends. This technology enables precise temperature calibration within the sample chamber and accurately indicates the temperature gradient at both ends of the sample chamber, ensuring that the zinc spinel sample is kept in a stable isothermal zone during the synthesis process.

[0090] Step 26: After maintaining a constant temperature and pressure for 72 hours at 3.0 GPa and 1050 °C, the temperature inside the sample chamber is reduced from 1050 °C to 800 °C at a cooling rate of 3 °C / min, and held at that temperature for 1 hour. Then, the temperature inside the sample chamber is reduced from 800 °C to room temperature at a cooling rate of 5 °C / min. This step-by-step cooling and the relatively slow constant-pressure cooling rate relative to the sample preparation rate (10 °C / min) further enhance the superior physicochemical properties of the cobalt-doped zinc spinel single crystal sample, which exhibits uniform cobalt distribution, high mechanical strength, and high density. It completely avoids the uneven stress caused by excessively rapid cooling, which could lead to cracks and breakage in the zinc spinel crystal. Furthermore, this preparation process is more conducive to the growth of large-particle zinc spinel single crystals, thus enabling the preparation of zinc spinel large-particle single crystal samples at the hundred-micron scale.

[0091] Step 27: After the temperature inside the sample chamber drops to room temperature, the pressure inside the sample chamber is reduced from 3.0 GPa to atmospheric pressure at a depressurization rate of 0.5 GPa / hour. Furthermore, this invention provides a process for preparing cobalt-doped anhydrous zinc spinel samples via hot-pressing sintering. The preparation process is pure, without the introduction of any potentially water-based substances from the sample itself or during high-pressure sample assembly.

[0092] Step 28: After the high-temperature and high-pressure preparation reaction is completed, the sample is removed from the typical 6–8 type multi-faceted top large-cavity high-temperature and high-pressure equipment of the Kawai-1000t. The graphite tube encasing the sample is carefully removed, and the cylindrical sample is cut in half from the center using a high-precision diamond wire cutter. Zinc spinel single crystals are then selected under a high-precision Olympus microscope at 20x magnification.

[0093] The zinc spinel single crystal obtained in this invention is a single phase without any other impurity phases; electron probe microanalysis (EPMA) results show that the molecular formula of the obtained zinc spinel single crystal is ZnAl2O4; multifunctional ion mass spectrometry (ICP-MS) results show that the cobalt content in the obtained zinc spinel single crystal is 7096 ppm wt%; vacuum Fourier transform infrared spectroscopy (FT-IR) results show that the water content of the obtained cobalt spinel sample is less than 4 ppm wt%, indicating a low water content and classifying it as an anhydrous oxide mineral.

[0094] The cobalt-doped anhydrous zinc spinel single crystal obtained in this invention is cubic with space group Fd3m (no. 227) and lattice parameters of [missing information]. α=β=γ=90°, unit cell volume is The average particle size is 132 micrometers, and the maximum particle size is 334 micrometers.

[0095] The cobalt-doped anhydrous zinc spinel single crystals obtained by this invention exhibit superior properties such as high purity, large grain size, stable chemical properties, and high mechanical strength. Most importantly, they possess a high cobalt content (7096 ppm wt%), and the cobalt content in the zinc spinel can be completely controlled. By changing the amount of the initial solid cobalt acetylacetone crystal added from 67.6414 mg to 90.1885 mg, the corresponding cobalt content in the obtained cobalt-doped anhydrous zinc spinel samples increased from 6000 ppm wt% to 8000 ppm wt%. The obtained cobalt-doped anhydrous zinc spinel fully meets the needs of physical experiments simulating minerals in the lower crust and upper mantle of Earth and other terrestrial planets under high temperature and high pressure conditions. This breakthrough overcomes the existing technical bottleneck in the synthesis of zinc spinel single crystals and provides important experimental sample support for studying the optimal lattice orientation and crystal axis anisotropy of single-crystal minerals in the lower crust and upper mantle of Earth and other terrestrial planets under high temperature and high pressure conditions.

Claims

1. A process for the preparation of a cobalt doped anhydrous zinc spinel single crystal at high temperature and high pressure, characterized by: The method comprises: preparing a zinc spinel powder sample mixture by taking solid basic zinc carbonate powder, solid aluminum isopropyl alcohol powder, solid oxalic acid powder, solid acetylacetone cobalt crystal and liquid dilute nitric acid as starting materials; cold-pressing the zinc spinel powder sample mixture into sample discs, stacking the sample discs vertically together and placing them in a graphite crucible to calcine in a high-temperature oxygen atmosphere furnace, and obtaining a glassy zinc spinel sample powder after quenching; cold-pressing the glassy zinc spinel sample powder into a cylindrical sample, sealing the cylindrical sample in a graphite tube and then placing it in a high-temperature high-pressure device to perform a high-temperature high-pressure reaction, and finally obtaining a cobalt-doped anhydrous zinc spinel single crystal; The method for obtaining the glassy zinc spinel sample powder comprises: Step 15: stacking three sample discs vertically together and placing them in the wall of a graphite crucible, and hanging the graphite crucible in the middle of a high-temperature oxygen atmosphere furnace; connecting the two ends of the platinum-rhodium wire of the graphite crucible to the vertical four-hole alumina tube, and fixing the upper end of the four-hole alumina tube to the middle of the round cover that can be put into or pulled out of the furnace body at any time; Step 16: placing a stainless steel container containing secondary deionized pure cold water on the side of the high-temperature oxygen atmosphere furnace; Step 17: connecting the top end of the furnace body of the high-temperature oxygen atmosphere furnace to the argon inert gas cylinder, the proportionally adjustable carbon monoxide and carbon dioxide cylinders; Step 18: opening the argon inert gas valve for continuous inflation for 30 minutes; under the protection of argon inert gas, increasing the temperature of the high-temperature oxygen atmosphere furnace to 800 °C at a rate of 400 °C / hour; Step 19: after the temperature in the furnace body reaches 800 °C, switching the carbon monoxide gas and carbon dioxide gas control valves to make the volume ratio of carbon monoxide and carbon dioxide in the sample oxygen atmosphere furnace reach 4:1; Step 20: increasing the temperature of the sample chamber in the furnace body to 1400 °C at a rate of 200 °C / hour, and constant temperature calcining for 15 minutes; Step 21: pulling out the graphite crucible containing the sample, the four-hole alumina tube and the round cover on the furnace body together from the furnace body, and directly immersing them in the secondary deionized pure water to quench into glassy zinc spinel; Step 22: taking the quenched glassy zinc spinel out of the graphite crucible, placing it in a corundum mortar for grinding into powder, and placing the glassy zinc spinel powder in a vacuum drying box under the condition of 200 °C for drying for 12 hours, to obtain a glassy zinc spinel sample powder; The method for obtaining the glassy zinc spinel sample powder comprises: Step 23: cold-pressing the glassy zinc spinel powder on a cold isostatic pressing machine with a Φ 4.0 mm diameter × 10.0 mm tungsten carbide grinding tool to obtain a cylindrical sample with a diameter of Φ 4.0 mm × 4.0 mm; Step 24: sealing the cylindrical sample in a graphite tube with an inner diameter of Φ 4.0 mm × 4.4 mm and a wall thickness of 0.2 mm, and blocking the upper and lower ends of the graphite tube with graphite sheets; Step 25, the plugged graphite tube is placed on the laboratory Kawai-1000t typical 6-8 type multi-faceted top large cavity high temperature and high pressure equipment, and the pressure increasing rate and temperature increasing rate are set to 0.5 GPa / hour and 10 °C / minute respectively, the pressure and temperature are increased to 3.0 GPa and 1050 °C respectively, and the hot-pressing sintering is performed, and the reaction time is 72 hours of constant temperature and constant pressure; Step 26, after 72 hours of constant temperature and constant pressure, the temperature in the sample cavity is reduced from 1050 °C to 800 °C at a cooling rate of 3 °C / minute, and the temperature is kept constant for 1 hour; then the temperature in the sample cavity is reduced from 800 °C to room temperature at a cooling rate of 5 °C / minute; Step 27, after the temperature in the sample cavity is reduced to room temperature, the pressure in the sample cavity is reduced from 3.0 GPa to normal pressure at a depressurization rate of 0.5 GPa / hour; Step 28, after the high temperature and high pressure reaction is completed, the graphite tube is taken out from the Kawai-1000t typical 6-8 type multi-faceted top large cavity high temperature and high pressure equipment; except the graphite tube wrapped with the sample, the cobalt-doped anhydrous zinc spinel single crystal is obtained.

2. The method for preparing cobalt-doped anhydrous zinc spinel single crystal under high temperature and high pressure according to claim 1, characterized in that: The purity of the solid basic zinc carbonate powder is >99.99%, the purity of the solid aluminum isopropoxide powder is >99.99%, the purity of the solid oxalic acid powder is >99.99%, the purity of the solid cobalt acetylacetonate crystal is >99.99%, and the concentration of the liquid dilute nitric acid is 10%.

3. The method for preparing cobalt-doped anhydrous zinc spinel single crystal under high temperature and high pressure according to claim 1, characterized in that: The preparation method of the zinc spinel powder sample mixture comprises: Step 1, 60 milliliters of dilute nitric acid with a concentration of 10% is weighed and placed in a 500 milliliter notch beaker; Step 2, 5.0 grams of basic zinc carbonate powder is weighed and added to the notch beaker, and a magnetic stirring rotor is placed in the notch beaker; Step 3, the notch beaker is covered with a glass surface dish; Step 4, according to the stoichiometric ratio of zinc spinel (Zn, Co) Al2O4, 17.9079 grams of solid aluminum isopropoxide powder and 80 milligrams of solid cobalt acetylacetonate crystal are weighed and added to the dilute nitric acid solution containing the basic zinc carbonate, respectively; Step 5, the notch beaker is covered with a glass surface dish; Step 6, the notch beaker is placed on a high-temperature magnetic stirring hot plate in a fume hood, and stirred at a speed of 800 revolutions / minute at room temperature for 48 hours; Step 7, 2 grams of solid oxalic acid powder is weighed and placed in the notch beaker; Step 8, after covering the glass surface dish, the high-temperature magnetic stirring hot plate is stirred at a parameter of 80 °C and a speed of 1000 revolutions / minute for 36 hours; Step 9, the glass surface dish of the beaker is removed, the temperature of the high-temperature magnetic stirring hot plate is adjusted to 110 °C, and the mixed solution in the entire notch beaker is evaporated until it is completely dry; Step 10, the mixed powder in the notch beaker is taken out and placed in a graphite crucible; Step 11, the graphite crucible containing the mixed powder is placed in a muffle furnace, the temperature is increased to 1100 °C at a rate of 300 °C / hour, and the temperature is kept constant for 5 hours; Step 12, after the mixture powder in the muffle furnace is reduced to room temperature at a rate of 200 °C / hour, the mixture sample powder is taken out. Step 13, put the sample powder into a corundum mortar and grind for 1 hour to obtain a zinc spinel powder sample mixture.

4. The method for preparing cobalt-doped anhydrous zinc spinel single crystal under high temperature and high pressure according to claim 1, characterized in that: The method for cold-pressing the zinc spinel powder sample mixture into a sample disc includes: Step 14, cold-press the zinc spinel powder sample mixture into a sample disc with a diameter of 10.0 mm and a thickness of 3.0 mm using a tungsten carbide die of a stainless steel tablet press.

5. The method for preparing cobalt-doped anhydrous zinc spinel single crystal under high temperature and high pressure according to claim 1, characterized in that: During the high temperature and high pressure reaction, the temperature is calibrated by two groups of high temperature resistant tungsten-rhenium thermocouples. Each group of tungsten-rhenium thermocouples is composed of two tungsten-rhenium alloys with different materials, and the chemical composition is W 95% Re 5% and W 74% Re 26% ; each group of tungsten-rhenium thermocouples is symmetrically placed at the upper and lower ends of the graphite tube sample cavity.