High-density magnesium oxide target material, method for preparing same, and use thereof

Abstract

The application provides a high-density magnesium oxide target material and a preparation method and application thereof, and belongs to the technical field of new material manufacturing and application. The application obtains a slurry by mixing a magnesium source powder raw material, a solvent and a functional additive and then sand grinding; then the slurry is pressure grouted and pressure-kept to obtain a target material blank; finally, the target material blank is sequentially subjected to drying treatment, degreasing and sintering to obtain a high-density magnesium oxide ceramic target material. In the preparation process, no sintering additive is used, and no hot pressing method is adopted, so that the problem of insufficient purity caused by the sintering additive and carbon pollution is solved, the degreasing and sintering steps are combined to simplify the preparation process, the preparation process is performed under normal pressure, the cost and operation difficulty are reduced, and the application is suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of new material manufacturing and application, and specifically relates to a high-density magnesium oxide target material and a preparation method and application thereof. Background Art

[0002] With the development of semiconductor technology, giant magnetoresistance (GMR) and tunnel magnetoresistance (TMR) devices have broad application prospects. The magnetic tunnel junction (MTJ) is the core element of GMR and TMR devices. It integrates magnetic materials and non-magnetic spacer layers based on multi-layer thin films, and the spacer layers or tunnel barriers are all ultra-thin insulators. Magnesium oxide (MgO) has advantages such as high-temperature stability, high dielectric properties, and low dielectric loss. When used as a magnetic tunnel junction (MTJ) isolation layer, the MTJ has a huge magnetoresistance effect at room temperature. Therefore, MgO films are widely used in the new generation of non-volatile high-density magnetic memories. Currently, MgO films are usually deposited by magnetron sputtering MgO targets. The target material performance directly affects the film performance, so it is crucial to prepare high-purity, high-density, and fine-grained MgO targets.

[0003] At present, the main methods for preparing MgO targets include vacuum or atmospheric sintering, hot pressing, etc. Patent CN106587940B discloses a magnesium oxide target with a density of 98.32% prepared by cold isostatic pressing and vacuum sintering; Patent CN107417260A and Patent 103917687B both use hot pressing to prepare magnesium oxide targets. Patent CN103917687B uses hot pressing followed by annealing at 1250-1400°C for 10 hours to obtain a magnesium oxide target with a relative density of 98-99%; Patent CN102225862A discloses a method of adding silicon-containing oxides, hydrogen A method for preparing a magnesium oxide target material by atmospheric sintering using oxides or organic matter as sintering aids; Patent CN116874284A uses cold isostatic pressing and hot pressing to prepare a magnesium oxide target material with a density of 98%; Patent CN102086504A dissolves organic polymer monomers, crosslinking agents, and dispersants into a toluene solution and mixes them with magnesium oxide to form a slurry. After slip casting, the slurry is sintered at 1650-1850°C for 3-5h to prepare a magnesium oxide target material with a relative density of 99.99%, but yttrium oxide is added as a sintering aid.

[0004] In summary, adding sintering aids is not conducive to improving the purity of MgO target, while atmospheric pressure sintering or vacuum sintering is difficult to further improve the density of the target. Hot pressing sintering has the problem of carbon pollution, and the mold is expensive and the shape and size are greatly limited.

[0005] Therefore, there is an urgent need for a method for preparing high-density MgO targets under normal pressure conditions without using sintering aids. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a high-density magnesium oxide target material and its preparation method and application. The preparation method adopted by the present invention is simple, does not require high pressure conditions and sintering aids, and the prepared target material has high purity, controllable shape, and a density of more than 99.5%.

[0007] The mold cost is low.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a high-density magnesium oxide target, comprising the following steps:

[0010] 1) mixing a magnesium source powder raw material, a solvent, and a functional additive and then sand-milling the mixture to obtain a slurry;

[0011] 2) The slurry is subjected to pressure injection and pressure maintenance to obtain a target blank;

[0012] 3) The target blank is dried, degreased and sintered in sequence to obtain a high-density magnesium oxide ceramic target.

[0013] Preferably, in step 1), the mass ratio of the magnesium source powder raw material, the solvent, and the functional additive is: 60-80:20-40:0.5-6.5.

[0014] Preferably, the purity of the magnesium source powder is 3N or above, the powder morphology is spherical, the average particle size of the powder is 50-500nm, and the specific surface area is 7-30m 2 / g.

[0015] Preferably, the magnesium source powder raw material is nano magnesium oxide or magnesium hydroxide.

[0016] Preferably, the solvent is water or an organic solvent.

[0017] More preferably, the organic solvent is ethanol or isopropanol.

[0018] Preferably, the functional auxiliary agent is at least one of a dispersant, a binder, and a defoaming agent.

[0019] More preferably, the dispersant is at least one of polyacrylic acid, polycarboxylic acid or ammonium citrate; the binder is at least one of carboxymethyl cellulose, ethyl cellulose, acrylic resin or polyvinyl alcohol carboxybutyral; and the defoamer is at least one of n-butanol, polydimethylsiloxane or fatty acid.

[0020] More preferably, the functional additives are a dispersant, a binder, and a defoamer; the mass ratio of the dispersant, binder, and defoamer is 1-4:1-8:0.1-4. Experiments have shown that the use of the dispersant, binder, and defoamer can improve the density of the target material.

[0021] Preferably, the grinding balls used for sand grinding in step 1) are zirconia balls.

[0022] More preferably, the sanding speed is 1500-2000 r / min, and the sanding time is 40-80 min.

[0023] Preferably, in step 1), the slurry has a solid content of 60-80% and a viscosity of 40-70 mPa·s.

[0024] Preferably, the step 2) further includes vacuum degassing before pressure grouting, with the vacuum pressure being less than 0.2 Pa. By adopting the above technical solution, the removal of bubbles in the system facilitates the subsequent steps and improves the density.

[0025] Preferably, nitrogen is used to maintain pressure during the pressure grouting in step 2), and the pressure is maintained at 0.2-0.8 MPa for 2-10 hours.

[0026] Preferably, the step 2) is performed by pressure grouting in a mold, such as a water-absorbent mold such as gypsum.

[0027] Preferably, the drying conditions in step 3) are:

[0028] The first drying is carried out for 24-36 hours at a first drying temperature of 20-35°C and a first humidity of 70-80% RH;

[0029] Then, a second drying is performed at a second drying temperature of 40-60° C. and a second humidity of 50-70% RH for 36-48 hours.

[0030] By adopting the above technical solution, the cracking of the green body can be prevented through multi-step drying.

[0031] Preferably, the debinding and sintering process in step 3) is carried out in a flowing oxygen environment;

[0032] The debinding and sintering process was carried out according to the following step temperature change program: the temperature was increased from room temperature to the first step of 350°C at a heating rate of 0.5°C / min, and kept warm for 15 hours; the temperature was increased to the second step of 800°C at a heating rate of 0.5°C / min, and kept warm for 20 hours; the temperature was increased to the third step of 1300-1800°C at a heating rate of 3°C / min, and kept warm for 6 hours; the temperature was cooled to the fourth step of 300-500°C at a cooling rate of 3°C / min, and kept warm for 2 hours, and then naturally cooled to room temperature.

[0033] In a second aspect, the present invention provides a high-density magnesium oxide target material prepared by the above-mentioned preparation method.

[0034] In a third aspect, the present invention provides applications of the above-mentioned high-density magnesium oxide target in magnetic storage and superconductivity.

[0035] Beneficial technical effects:

[0036] The present invention is carried out by mixing magnesium source powder raw materials, solvents, and functional additives and then sand-grinding to obtain a slurry; then the slurry is subjected to pressure grouting and pressure maintenance to obtain a target blank; finally, the target blank is sequentially dried, degreased, and sintered to obtain a high-density magnesium oxide ceramic target. The blank obtained by grouting is pre-sintered in the degreasing process and is in the initial stage of densification. In the high-temperature stage, the grains grow and densify. The synergistic effect of the two enables magnesium oxide to achieve high densification without sintering aids and pressure. In the preparation process, no sintering aids are used, and no hot pressing method is adopted, so there is no problem of insufficient purity caused by sintering aids and carbon pollution. At the same time, the combination of degreasing and sintering steps simplifies the preparation process. It can be carried out under normal pressure to reduce costs and operational difficulty, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a SEM image of the magnesium oxide target prepared in Example 1;

[0038] Figure 2 This is the XRD pattern of the magnesium oxide target prepared in Example 2. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0040] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0041] Example 1

[0042] This embodiment provides a method for preparing a high-density magnesium oxide target, comprising the following steps:

[0043] 1) nano-magnesium oxide, anhydrous ethanol, polyacrylic acid, carboxymethyl cellulose, and n-butanol were weighed and mixed, and the mixture was sand-milled (using zirconium oxide balls) at 1800 r / min for 60 min to obtain a magnesium oxide slurry having a solid content of 80% and a viscosity of 42.1 mPa·s;

[0044] The weight ratio of nano-magnesium oxide, anhydrous ethanol, polyacrylic acid, carboxymethyl cellulose and n-butanol is 80:20:0.8:0.8:0.5; the nano-magnesium oxide is a spherical powder with an average particle size of 300 nm, a powder purity of 3N5 (99.95%), and a specific surface area of ​​8 m 2 / g.

[0045] 2) The sand-milled magnesium oxide slurry is vacuumed and defoamed to a vacuum pressure of less than 0.15 Pa. Nitrogen is introduced for pressure grouting, with the pressure maintained at 0.5 MPa for 8 hours. After demolding, a magnesium oxide target blank with a density of 58% is obtained;

[0046] 3) drying the magnesium oxide target blank; the drying process adopts a two-step constant temperature and humidity drying process, wherein the first drying is carried out for 24 hours at a first drying temperature of 25° C. and a first humidity of 80% RH; and the second drying is carried out for 36 hours at a second drying temperature of 40° C. and a second humidity of 70% RH;

[0047] After drying, place it in a sintering furnace with flowing oxygen atmosphere, and heat it from room temperature to the first step of 350℃ at a heating rate of 0.5℃ / min, and keep it warm for 15h; heat it to the second step of 800℃ at a heating rate of 0.5℃ / min, and keep it warm for 20h; heat it to the third step of 1500℃ at a heating rate of 3℃ / min, and keep it warm for 6h; cool it to the fourth step of 400℃ at a cooling rate of 3℃ / min, keep it warm for 2h, and cool it naturally to room temperature.

[0048] After the Archimedes drainage method test, the relative density of the obtained magnesium oxide target is 99.67%; the SEM image of the obtained magnesium oxide target is as follows Figure 1 As shown, there are no obvious pores.

[0049] Example 2

[0050] This embodiment provides a method for preparing a high-density magnesium oxide target, comprising the following steps:

[0051] 1) magnesium hydroxide, anhydrous ethanol, polycarboxylic acid, ethyl cellulose, and polydimethylsiloxane were weighed and mixed, and the mixture was sand-milled (using zirconium oxide balls) at 1800 r / min for 60 min to obtain a magnesium oxide slurry having a solid content of 75% and a viscosity of 60.2 mPa·s;

[0052] The weight ratio of nano-magnesium oxide, anhydrous ethanol, polycarboxylic acid, ethyl cellulose and polydimethylsiloxane is 75:25:0.8:0.8:0.5; the nano-magnesium oxide is a spherical powder with an average particle size of 300 nm, a powder purity of 99%, and a specific surface area of ​​8 m 2 / g.

[0053] 2) The sand-milled magnesium hydroxide slurry is subjected to vacuum degassing treatment, with the vacuum pressure being less than 0.15 Pa. Nitrogen is introduced for pressure grouting, with the pressure maintained at 0.5 MPa for 4 hours. After demolding, a magnesium oxide target blank with a density of 56% is obtained;

[0054] 3) drying the magnesium oxide target blank; the drying process adopts a two-step constant temperature and humidity drying process, wherein the first drying is carried out for 24 hours at a first drying temperature of 25° C. and a first humidity of 80% RH; and the second drying is carried out for 36 hours at a second drying temperature of 40° C. and a second humidity of 70% RH;

[0055] After drying, place it in a sintering furnace with flowing oxygen atmosphere, and heat it from room temperature to the first step of 350℃ at a heating rate of 0.5℃ / min, and keep it warm for 15h; heat it to the second step of 800℃ at a heating rate of 0.5℃ / min, and keep it warm for 20h; heat it to the third step of 1500℃ at a heating rate of 3℃ / min, and keep it warm for 6h; cool it to the fourth step of 400℃ at a cooling rate of 3℃ / min, keep it warm for 2h, and cool it naturally to room temperature.

[0056] After testing by the Archimedes drainage method, the relative density of the obtained magnesium oxide target was 99.58%.

[0057] Example 3

[0058] This embodiment provides a method for preparing a high-density magnesium oxide target, comprising the following steps:

[0059] 1) nano-magnesium oxide, water, ammonium citrate, acrylic resin, and fatty acid were weighed and mixed, and the mixture was sand-milled (using zirconium oxide balls) at 1500 r / min for 40 min to obtain a magnesium oxide slurry having a solid content of 70% and a viscosity of 45.6 mPa·s;

[0060] The weight ratio of nano-magnesium oxide, water, ammonium citrate, acrylic resin and fatty acid is 70:30:0.7:1:0.1; the nano-magnesium oxide is a spherical powder with an average particle size of 100 nm, a powder purity of 99.9%, and a specific surface area of ​​7 m 2 / g.

[0061] 2) The sand-milled magnesium oxide slurry is vacuumed and defoamed to a vacuum pressure of less than 0.15 Pa. Nitrogen is introduced for pressure grouting, with the pressure maintained at 0.5 MPa for 8 hours. After demolding, a magnesium oxide target blank with a density of 58% is obtained;

[0062] 3) drying the magnesium oxide target blank; the drying process adopts a two-step constant temperature and humidity drying process, wherein the first drying is carried out for 30 hours at a first drying temperature of 20° C. and a first humidity of 60% RH; and the second drying is carried out for 40 hours at a second drying temperature of 50° C. and a second humidity of 60% RH;

[0063] After drying, place it in a sintering furnace with flowing oxygen atmosphere, heat it from room temperature to the first step of 400℃ at a heating rate of 1℃ / min, and keep it warm for 6 hours; heat it to the second step of 750℃ at a heating rate of 2℃ / min, and keep it warm for 12 hours; heat it to the third step of 1600℃ at a heating rate of 2.5℃ / min, and keep it warm for 4 hours; cool it to the fourth step of 400℃ at a cooling rate of 2℃ / min, keep it warm for 3 hours, and cool it naturally to room temperature.

[0064] After testing by the Archimedes drainage method, the relative density of the obtained magnesium oxide target was 99.52%.

[0065] Example 4

[0066] This embodiment provides a method for preparing a high-density magnesium oxide target. The only difference from Example 1 is that in step 1), the raw materials are nano-magnesium oxide, anhydrous ethanol, and polyacrylic acid in a weight ratio of 80:20:2.

[0067] Example 5

[0068] This embodiment provides a method for preparing a high-density magnesium oxide target. The only difference from Example 1 is that in step 1), the raw materials are nano-magnesium oxide, anhydrous ethanol, and carboxymethyl cellulose in a weight ratio of 80:20:1.5.

[0069] Example 6

[0070] This embodiment provides a method for preparing a high-density magnesium oxide target, which is different from Example 1 only in that the raw materials in step 1) are nano-magnesium oxide, anhydrous ethanol, and n-butanol in a weight ratio of 80:20:1.

[0071] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a high-density magnesium oxide target, characterized in that: The following steps are involved: 1) mixing a magnesium source powder raw material, a solvent, and a functional additive and then sand-milling the mixture to obtain a slurry; 2) The slurry is subjected to pressure injection and pressure maintenance to obtain a target blank; 3) The target blank is dried, degreased and sintered in sequence to obtain a high-density magnesium oxide ceramic target; Step 2) Nitrogen is used to maintain pressure during pressure grouting, the pressure is maintained at 0.2-0.8 MPa, and the pressure holding time is 2-10 hours; The conditions for the drying process in step 3) are: The first drying is carried out for 24-36 hours at a first drying temperature of 20-35°C and a first humidity of 70-80% RH; Then, the second drying is carried out for 36-48 hours under the conditions of the second drying temperature of 40-60°C and the second humidity of 50-70% RH; The degreasing and sintering process in step 3) is carried out in a flowing oxygen environment; The debinding and sintering process was carried out according to the following step temperature change program: the temperature was increased from room temperature to the first step of 350°C at a heating rate of 0.5°C / min, and kept warm for 15 hours; the temperature was increased to the second step of 800°C at a heating rate of 0.5°C / min, and kept warm for 20 hours; the temperature was increased to the third step of 1300-1800°C at a heating rate of 3°C / min, and kept warm for 6 hours; the temperature was cooled to the fourth step of 300-500°C at a cooling rate of 3°C / min, and kept warm for 2 hours, and then naturally cooled to room temperature.

2. The preparation method according to claim 1, characterized in that In the step 1), the mass ratio of the magnesium source powder raw material, the solvent, and the functional additive is: 60-80:20-40:0.5-6.

5.

3. The preparation method according to claim 2, characterized in that The purity of the magnesium source powder is 3N or above, the powder morphology is spherical, the average particle size of the powder is 50-500nm, and the specific surface area is 7-30m 2 / g; the magnesium source powder raw material is nano magnesium oxide or magnesium hydroxide.

4. The preparation method according to claim 2, characterized in that The solvent is water or an organic solvent.

5. The preparation method according to claim 2, characterized in that The functional auxiliary agent is at least one of a dispersant, a binder, and a defoaming agent.

6. The preparation method according to claim 5, characterized in that The dispersant is at least one of polyacrylic acid, polycarboxylic acid or ammonium citrate; the binder is at least one of carboxymethyl cellulose, ethyl cellulose, acrylic resin or polyvinyl alcohol carboxybutyral; and the defoamer is at least one of n-butanol, polydimethylsiloxane or fatty acid.

7. Application of the high-density magnesium oxide target prepared by the preparation method according to any one of claims 1 to 6 in magnetic storage and superconductivity.

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