High-density nickel magnesia target material and method for manufacturing the same

Abstract

The application belongs to the field of perovskite solar cell materials, and discloses a high-density nickel-magnesium oxide target material and a preparation method thereof. The preparation method comprises the following steps: NiO powder and MgO powder are proportioned according to the atomic percentage of Mg of 0.1-10 at%, the prepared powder is loaded into a double-motion mixer for homogenizing mixing treatment, then the uniformly mixed powder is cold-pressed to 5-10 MPa, vacuumized to less than 10 Pa, heated to 300-400 DEG C for heat preservation and pretreatment, heated to 1000-1200 DEG C and pressurized to 30-50 MPa for hot-pressing sintering to obtain a target blank; and the obtained blank target is sequentially subjected to diamond grinding and water cutting to obtain the high-density nickel-magnesium oxide target material. The preparation method is simple in operation and low in cost, the prepared target material is uniform in composition, good in conductivity, free of internal defects, high in density, and meets the requirements of a sputtering target.

Description

Technical Field

[0001] This invention belongs to the field of perovskite solar cell materials, specifically relating to a high-density nickel-magnesium-oxygen target and its preparation method. Background Technology

[0002] Perovskite solar cells are becoming competitors to commercial solar energy technologies by combining high efficiency with low-cost solutions. The hole transport layer is an indispensable component of traditional perovskite solar cells. The hole transport layer plays a crucial role in improving the performance of perovskite solar cells by increasing hole collection, blocking electrons, and protecting the perovskite from external influences such as moisture, heat, and oxygen. Nickel oxide (NiOx), as a commonly used hole transport material, has a wide band gap (e.g., 3.6-4.0 eV) and a deep valence band maximum, resulting in high optical transparency, efficient charge extraction, high hole mobility, and low manufacturing cost, making it a promising candidate for various photovoltaic devices. Methods for preparing corresponding nickel oxide-based targets are disclosed in patents CN112441819A, CN112456971A, CN112481592A, CN115536368A, and CN115650701A. They are generally prepared using processes such as spray drying powder preparation, cold isostatic pressing, and hot pressing sintering to meet the performance requirements of nickel oxide targets for perovskite solar cells.

[0003] However, NiOx, as a typical hole transport layer, is easily affected by the synthesis method and post-processing conditions in applications. This is because perovskite solar cells with pure NiOx hole transport layers typically struggle to achieve high efficiency due to interfacial losses. Inevitable surface defects and charged chemical substances at the interface hinder the achievement of high power conversion efficiency and long-term operational stability; surface defects increase charge recombination, reducing open-circuit voltage, fill factor, and short-circuit current density; charged chemical substances lead to perovskite decomposition, reducing the stability of the perovskite solar cell. Research has found that adding Mg to NiO can increase conductivity and reduce interfacial losses, thereby improving high-power conversion efficiency. Therefore, the requirements for nickel-magnesium-oxygen targets used in sputtering are extremely high, with strict requirements on magnesium uniformity, target density, purity, and grain size. Therefore, a method for preparing high-performance nickel-magnesium-oxygen targets is needed.

[0004] In our previous patent CN 116768606 A, we disclosed a method for preparing a composite nickel-magnesium oxide target material. The method mainly includes the following steps: first, mixing NiO powder and MgO powder, ball milling, and sieving to obtain a mixed NiO and MgO powder; then, subjecting the obtained NiO and MgO mixed powder to molding, pre-pressing, vacuum hot pressing, and demolding to obtain a nickel-magnesium oxide blank; finally, machining the obtained nickel-magnesium oxide blank to obtain the nickel-magnesium oxide target material. This method mainly improves the uniformity and relative density of the target material by controlling the ball milling conditions. However, the ball milling process is long, has a long cycle time, and is costly. Furthermore, the relative density and conductivity of the nickel-magnesium oxide prepared by this method have room for further improvement. Summary of the Invention

[0005] In view of the shortcomings and deficiencies of the existing technology, the primary objective of this invention is to provide a high-density nickel-magnesium-oxygen target and its preparation method.

[0006] Another object of the present invention is to provide a high-density nickel-magnesium-oxygen target material prepared by the above method.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a high-density nickel-magnesium-oxygen target material includes the following preparation steps:

[0009] (1) Batching: NiO powder and MgO powder are mixed according to the atomic percentage of Mg being 0.1 to 10 at%.

[0010] (2) Homogenization: The prepared powder is loaded into a dual-motion mixer for homogenization and mixing;

[0011] (3) Hot pressing sintering: After the powder mixed evenly in step (2) is cold pressed to 5-10 MPa, the vacuum is drawn to less than 10 Pa, and then the temperature is raised to 300-400℃ and kept for 0.5-2 h for pretreatment. Then the temperature is raised to 1000-1200℃ and the pressure is increased to 30-50 MPa for hot pressing sintering to obtain the target blank.

[0012] (4) Target blank processing: The obtained target blank is ground with diamond grinding wheel and cut with water jet to obtain high-density nickel magnesium oxide target material.

[0013] Preferably, the NiO powder in step (1) has a purity greater than 99.99%, a particle size D90 of 1–10 μm, and a BET specific surface area of ​​0.5–10 m². 2 / g. More preferably, the powder particle size D90 is 2–10 μm, and the powder BET specific surface area is 0.8–9.5 m². 2 / g.

[0014] Preferably, the MgO powder in step (1) has a purity greater than 99.99% and a particle size D90 of 1–10 μm. More preferably, the particle size D90 is 1–5 μm.

[0015] Preferably, in step (2), the rotational speed of the barrel for homogenization in the dual-motion mixer is 10-20 r / min, the rotational speed of the blades is 20-40 r / min, and the homogenization time is 15-30 h.

[0016] Preferably, the pressurization rate of cold pressing to 5-10 MPa and pressurization to 30-50 MPa in step (3) is 0.1-0.6 MPa / min.

[0017] Preferably, the heating rate in step (3) for heating to 300-400°C and heating to 1000-1200°C is 5-10°C / min.

[0018] Preferably, the heat preservation pretreatment time in step (3) is 0.5 to 2 hours, more preferably 1 hour; the hot pressing sintering time is 1 to 4 hours, more preferably 3 to 4 hours.

[0019] Preferably, the diamond grinding wheel used in step (4) is 200-400 mesh and rotates at a speed of 200-400 r / min.

[0020] Preferably, the cutting rate of the water jet cutting in step (4) is 40 to 100 mm / min.

[0021] A high-density nickel-magnesium-oxygen target material is prepared by the above method; the high-density nickel-magnesium-oxygen target material has a relative density ≥98.8% and a resistivity <10KΩ·cm.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] (1) The preparation method of the present invention uses a dual-motion mixer to homogenize NiO powder and MgO powder, then sintersulates them by vacuum hot pressing, and then processes them into sputtering targets. This preparation method is simple to operate and low in cost. The target material prepared by this method has uniform composition, good conductivity, no internal defects, and high density, which meets the requirements of sputtering targets.

[0024] (2) The present invention further improves the uniformity and density of the target material by further controlling the particle size and specific surface area of ​​NiO powder, the rotation speed of the dual motion mixer, the pretreatment before hot pressing sintering, the hot pressing sintering temperature and pressure and the target blank processing conditions. Attached Figure Description

[0025] Figure 1 Here is a SEM image of the NiO powder in Example 1;

[0026] Figure 2 Here is a SEM image of the NiO powder in Comparative Example 1;

[0027] Figure 3 The image shows a SEM image of the NiO powder in Comparative Example 2. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0029] Example 1

[0030] This embodiment provides a method for preparing a high-density nickel-magnesium-oxygen target, comprising the following preparation steps:

[0031] (1) Ingredients: Prepare NiO powder with a purity greater than 99.99%, a particle size D90 of 10 μm, and a BET specific surface area of ​​0.8 m². 2 / g, SEM image of NiO powder as shown in the figure Figure 1 As shown; prepare MgO powder with a purity greater than 99.99%, a particle size D90 of 1μm, and a feeding ratio of 0.1at%.

[0032] (2) Homogenization: The prepared powder was loaded into a double-motion mixer and homogenized for 18 hours at a drum speed of 15 r / min and a blade speed of 30 r / min. After homogenization, three points (top, middle, and bottom) were sampled using a special sampler to detect the Mg content.

[0033] (3) Hot pressing sintering: The uniformly mixed powder is cold pressed to 5 MPa at 0.4 MPa / min, then vacuumed to less than 10 Pa. The temperature is raised to 300℃ at a rate of 10℃ / min and held for 1 h. Then the temperature is raised to 1050℃ at a rate of 10℃ / min and then pressurized to 40 MPa at a rate of 0.5 MPa / min. The holding time is 3 h. After the holding time is over, the powder is cooled to room temperature with the furnace, the furnace door is opened, and the target blank is removed from the mold.

[0034] (4) Target blank processing: The obtained target blank is fixed on a surface grinder and ground with a diamond grinding wheel of 400 mesh at a speed of 300 r / min to obtain the target blank; then the outer circle is cut with water cutting at a water cutting rate of 80 mm / min, and a sample is taken at the same time to detect the Mg content.

[0035] (5) Bonding test: The target blank that has passed the processing test is bonded together with indium and copper backing plate to obtain the high-density nickel magnesium oxide target material of this embodiment.

[0036] The high-density nickel-magnesium-oxygen target obtained in this embodiment has a relative density of 99.0% as measured by the water displacement method; the resistivity of the four-probe test is 5.7 KΩ·cm; the Mg content at each point measured by ICP is 0.101 at%, 0.097 at%, and 0.102 at%, with no color difference in appearance, and no internal defects detected by ultrasonic C-Scan, meeting the requirements for sputtering targets.

[0037] Example 2

[0038] This embodiment provides a method for preparing a high-density nickel-magnesium-oxygen target, comprising the following preparation steps:

[0039] (1) Ingredients: Prepare NiO powder with a purity greater than 99.99%, a particle size D90 of 10 μm, and a BET specific surface area of ​​0.8 m². 2 / g; Prepare MgO powder with a purity greater than 99.99%, a particle size D90 of 5μm, and a feeding ratio of 5at%.

[0040] (2) Homogenization: The prepared powder is loaded into a double-motion mixer and homogenized for 25 hours at a drum speed of 18 r / min and a blade speed of 30 r / min. After homogenization, three points (top, middle, and bottom) are sampled using a special sampler to test the Mg content and ensure that the MgO is mixed evenly.

[0041] (3) Hot pressing sintering: The uniformly mixed powder is cold pressed to 10 MPa at 0.5 MPa / min, then vacuumed to less than 10 Pa. The temperature is raised to 400℃ at a rate of 10℃ / min and held for 1 h. Then the temperature is raised to 1100℃ at a rate of 10℃ / min and then pressurized to 45 MPa at a rate of 0.6 MPa / min. The holding time is 4 h. After the holding time is over, the powder is cooled to room temperature with the furnace, the furnace door is opened, and the target blank is removed from the mold.

[0042] (4) Target blank processing: The obtained target blank is fixed on a surface grinder and ground with a diamond grinding wheel of 400 mesh at a speed of 300 r / min to obtain the target blank; then the outer circle is cut with water cutting at a water cutting rate of 70 mm / min, and a sample is taken at the same time to detect the Mg content.

[0043] (5) Bonding test: The target blank that has passed the processing test is bonded together with indium and copper backing plate to obtain the high-density nickel magnesium oxide target material of this embodiment.

[0044] The high-density nickel-magnesium-oxygen target obtained in this embodiment has a relative density of 98.9% as measured by the water displacement method; a resistivity of 4.5 KΩ·cm; and Mg content of 5.020 at%, 4.990 at%, and 5.011 at at various points. It has no color difference in appearance and no internal defects, meeting the requirements for sputtering targets.

[0045] Powders with a particle size D90 of 8 μm and a BET specific surface area of ​​1.2 m² were used. 2 / g; D90 is 4μm, BET specific surface area is 4.6m². 2 / g, D90 is 2μm, BET specific surface area is 9.5m² 2 NiO powder of [value] g was used as feedstock. Under the same conditions, the relative densities of the resulting nickel-magnesium-oxygen targets were 99.1%, 99.3%, and 99.6%, respectively; the resistivity measurements were 4.0 KΩ·cm, 3.2 KΩ·cm, and 2.7 KΩ·cm, respectively. These results indicate that the smaller the NiO powder particle size and the higher the specific surface area, the higher the relative density and conductivity of the resulting nickel-magnesium-oxygen targets. The optimal NiO powder particle size (D90) was 2–10 μm, and the BET specific surface area was 0.8–9.5 μm². 2 It can achieve high relative density and conductivity within the range of / g.

[0046] Example 3

[0047] This embodiment provides a method for preparing a high-density nickel-magnesium-oxygen target, comprising the following preparation steps:

[0048] (1) Ingredients: Prepare NiO powder with a purity greater than 99.99%, a particle size D90 of 10 μm, and a BET specific surface area of ​​0.8 m². 2 / g; Prepare MgO powder with a purity greater than 99.99%, a particle size D90 of 5μm, and a feeding ratio of 10at%.

[0049] (2) Homogenization: The prepared powder is loaded into a double-motion mixer and homogenized for 25 hours at a drum speed of 18 r / min and a blade speed of 30 r / min. After homogenization, three points (top, middle, and bottom) are sampled using a special sampler to test the Mg content and ensure that the MgO is mixed evenly.

[0050] (3) Hot pressing sintering: The uniformly mixed powder is cold pressed to 5 MPa at 0.4 MPa / min, then vacuumed to less than 10 Pa. The temperature is raised to 400℃ at a heating rate of 10℃ / min and held for 1 h. Then the temperature is raised to 1150℃ at a heating rate of 10℃ / min and then pressurized to 45 MPa at a pressurization rate of 0.6 MPa / min. The holding time is 4 h. After the holding time is over, the furnace is cooled to room temperature, the furnace door is opened, and the target blank in the mold is removed.

[0051] (4) Target blank processing: The obtained target blank is fixed on a surface grinder and ground with a diamond grinding wheel of 400 mesh at a speed of 300 r / min to obtain the target blank; then the outer circle is cut with water cutting at a water cutting rate of 70 mm / min, and a sample is taken at the same time to detect the Mg content.

[0052] (5) Bonding test: The target blank that has passed the processing test is bonded together with indium and copper backing plate to obtain the high-density nickel magnesium oxide target material of this embodiment.

[0053] The high-density nickel-magnesium-oxygen target obtained in this embodiment has a relative density of 98.8% as measured by the water displacement method; a resistivity of 3.5 KΩ·cm; and Mg content of 10.040 at%, 10.010 at%, and 9.990 at at various points. It has no color difference in appearance and no internal defects, meeting the requirements for sputtering targets.

[0054] Comparative Example 1

[0055] This comparative example describes a method for preparing a nickel-magnesium oxide target. Compared to Example 1, this method uses NiO powder with a particle size D90 of 20 μm and a BET specific surface area of ​​4.3 m². 2 / g, SEM image of NiO powder as shown in the figure Figure 2 As shown. All other conditions are the same.

[0056] The nickel-magnesium oxide target material obtained in this comparative example had a relative density of 96.2% and a resistivity of 7 KΩ·cm, as measured by the water displacement method. The Mg content was 0.121 at%, 0.085 at%, and 0.117 at%, and it had white spots on its appearance.

[0057] The comparison results between this comparative example and Example 1 show that excessively large D90 particle size of NiO powder leads to uneven mixing and low density.

[0058] Comparative Example 2

[0059] This comparative example describes a method for preparing a nickel-magnesium oxide target. Compared to Example 1, this method uses NiO powder with a particle size D90 of 1 μm and a BET specific surface area of ​​15 m². 2 / g, SEM image of NiO powder as shown in the figure Figure 3 As shown. All other conditions are the same.

[0060] After hot pressing and sintering, the comparative example showed numerous black pits on the target blank surface, each 3-4 mm in diameter and approximately 3 mm deep. SEM analysis of the powder revealed a flocculent morphology. This indicates that the NiO powder has excessively small particle size and a large specific surface area, resulting in high activity and a tendency for carburization to occur under the sintering conditions of this invention.

[0061] Comparative Example 3

[0062] This comparative example describes a method for preparing a nickel-magnesium oxide target. Compared to Example 1, this method uses NiO powder with a particle size D90 of 1 μm and a BET specific surface area of ​​15 m². 2 / g, while lowering the sintering temperature to 950℃, while keeping the rest unchanged.

[0063] The nickel-magnesium oxide target obtained in this comparative example had a relative density of 92.0% measured by the water displacement method. While carburization was reduced, white particles were observed to have detached, which were identified as MgO particles. This indicates that although lowering the sintering temperature can reduce carburization, excessively low sintering temperatures result in insufficient sintering of the MgO, leading to a lower relative density of the target.

[0064] Comparative Example 4

[0065] In this comparative example, a method for preparing a nickel-magnesium-oxygen target material is described. Compared with Example 2, the rotational speed of the dual-motion mixer blades in step (2) is increased to 60 r / min, while other steps remain unchanged.

[0066] In this comparative example, it was found that during material collection, the powder hardened and adhered to the blades or barrel wall due to heat generated by friction caused by excessive rotation speed. This indicates that the blade rotation speed of the dual-motion mixer used in this invention for homogenizing NiO and MgO powders should not be too high.

[0067] Comparative Example 5

[0068] The preparation method of the nickel-magnesium-oxygen target material in this comparative example is different from that in Example 2. The pretreatment process of holding at 400°C for 1 hour before hot pressing and sintering in step (3) is cancelled, while the others remain unchanged.

[0069] The nickel-magnesium oxide target obtained in this comparative example had a relative density of 97.0% and a resistivity of 5.4 KΩ·cm, as measured by the water displacement method. The Mg content was 5.001 at%, 4.998 at%, and 5.002 at%. However, there were black spots on the target surface. EDS analysis showed that only Ni and O elements were present in the black spots, but the proportions were slightly off.

[0070] The above results indicate that pretreatment at 400℃ before hot pressing and sintering can effectively remove gaseous substances adhering to NiO powder and prevent NiO from reacting with gases.

[0071] Comparative Example 6

[0072] The preparation method of the nickel-magnesium-oxygen target material in this comparative example is different from that in Example 2. In step (3), the hot pressing sintering temperature is increased to 1300℃ and the holding time is 2h, while the other steps remain unchanged.

[0073] The nickel-magnesium-oxygen target obtained in this comparative example had a relative density of 101.0% and a resistivity of 0.01 KΩ·cm, as measured by the water displacement method. The Mg content met the requirements, but the target surface had a metallic luster, which was determined to be metallic Ni by XRF scanning.

[0074] The above results indicate that the hot pressing sintering temperature was too high, and NiO underwent a reduction reaction with the mold and other components.

[0075] Comparative Example 7

[0076] The preparation method of the nickel-magnesium-oxygen target material in this comparative example is different from that in Example 2. The hot pressing sintering temperature in step (3) is reduced to 980°C, while the other steps remain unchanged.

[0077] The nickel-magnesium oxide target material obtained in this comparative example had a relative density of only 80% as measured by the water displacement method. The target material is non-conductive, and its density does not meet the requirements. This indicates that excessively low hot-pressing sintering temperatures lead to a decrease in the relative density and conductivity of the nickel-magnesium oxide target material of this invention.

[0078] Comparative Example 8

[0079] The preparation method of the nickel-magnesium-oxygen target in this comparative example is different from that in Example 3, the hot pressing pressure in step (3) is reduced to 25 MPa, while the others remain unchanged.

[0080] The nickel-magnesium-oxygen target obtained in this comparative example has a relative density of 88.0% as measured by the water displacement method, and the target is non-conductive.

[0081] The above results indicate that if the hot pressing pressure is too low, the resulting target material will not be dense enough and will have poor conductivity.

[0082] Comparative Example 9

[0083] In this comparative example, a method for preparing a nickel-magnesium-oxygen target material is used. Compared with Example 3, the hot pressing rate in step (3) is increased to 1 MPa / min, while the other steps remain unchanged.

[0084] In this comparative example, the nickel-magnesium-oxygen target blank cracked after demolding during the preparation process. This indicates that excessively rapid hot pressing can damage the target material.

[0085] Comparative Example 10

[0086] In this comparative example, a method for preparing a nickel-magnesium-oxygen target material is used. Compared with Example 3, the water cutting speed in step (4) is increased to 120 mm / min, while the others remain unchanged.

[0087] The nickel-magnesium-oxygen target obtained in this comparative example cracked at the edge after cutting. This indicates that excessive waterjet cutting speed and impact force can damage the target.

[0088] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for producing a high-density nickel magnesia target material, characterized by, The preparation method comprises the following steps: (1) batching: batching NiO powder and MgO powder according to the atomic percentage of Mg of 0.1-10 at%; (2) homogenization: loading the prepared powder into a double-motion mixer for homogenization and mixing treatment; (3) hot-pressing sintering: cold-pressing the uniformly mixed powder of step (2) to 5-10 MPa, vacuumizing to less than 10 Pa, then heating to 300-400 ℃ for heat preservation pretreatment, heating to 1000-1200 ℃ and pressurizing to 30-50 MPa for hot-pressing sintering to obtain a target blank; (4) target blank processing: grinding the surface of the obtained target blank by using a diamond grinding wheel and cutting the outer circle by water cutting to obtain a high-density nickel-magnesium oxide target material; The purity of the NiO powder in step (1) is greater than 99.99%, the powder particle size D90 is 1-10 μm, and the powder BET specific surface area is 0.5-10 m 2 / g. In step (2), the barrel rotation speed of the double-motion mixer for homogenization and mixing treatment is 10-20 r / min, and the blade rotation speed is 20-40 r / min; In step (3), the pressurizing rate for cold-pressing to 5-10 MPa and pressurizing to 30-50 MPa is 0.1-0.6 MPa / min; In step (4), the cutting rate of water cutting is 40-100 mm / min.

2. The method of claim 1, wherein the target material is prepared by the steps of: preparing a mixed powder of nickel and magnesium oxide; and sintering the mixed powder at a temperature of 1,000°C to 1,200°C in a non-oxidizing atmosphere. In step (1), the purity of the MgO powder is greater than 99.99%, and the powder particle size D90 is 1-10 μm.

3. The method of claim 1, wherein the target material is prepared by the steps of: preparing a mixed powder of nickel and magnesium oxide; and sintering the mixed powder at a temperature of 1,000°C to 1,200°C for 1 to 10 hours in a non-oxidizing atmosphere. In step (2), the homogenization and mixing treatment time of the double-motion mixer is 15-30 h.

4. The method of claim 1, wherein the target material is prepared by the steps of: preparing a mixed powder of nickel and magnesium oxide; and sintering the mixed powder at a temperature of 1,000°C to 1,200°C for 1 to 10 hours in a non-oxidizing atmosphere. In step (3), the heating rate for heating to 300-400 ℃ and heating to 1000-1200 ℃ is 5-10 ℃ / min.

5. The method of claim 1, wherein the target material is a high-density nickel magnesia target. In step (3), the heat preservation pretreatment time is 0.5-2 h, and the hot-pressing sintering time is 1-4 h.

6. The method of claim 1, wherein the target material is a high-density nickel magnesia target. In step (4), the diamond grinding wheel for surface grinding is 200-400 mesh, and the rotation speed is 200-400 r / min.

7. A high-density nickel magnesia target material, characterized by, The high-density nickel-magnesium oxide target material prepared by the method of any one of claims 1-6 has a relative density of ≥98.8% and an electric resistivity of <10 KΩ·cm.

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