Conductive nickel oxide target material and preparation method thereof

Abstract

The invention belongs to the technical field of target production, and discloses a conductive nickel oxide target preparation method, which comprises: mixing nickel oxide powder, nickel powder, an auxiliary agent and pure water to obtain a slurry, carrying out spray granulation, pre-pressing and calcination on the slurry to obtain a nickel oxide biscuit, and further sintering the nickel oxide biscuit to obtain the conductive nickel oxide target, the calcination is completed in an oxygen atmosphere, the particle size of the nickel oxide powder is 100-150 [mu] m, the particle size of the nickel powder is 50-75 [mu] m, and the mass ratio of the nickel oxide powder to the nickel powder is 99-99.8: 0.2-1; through the design, the nickel oxide target material which is not conductive originally contains a certain amount of nickel so as to achieve the conductive capacity of the nickel oxide target material, meanwhile, the density of the target material is improved through the auxiliaries, the auxiliaries are removed through the subsequent oxygen-containing calcination process, and in order to prevent nickel powder from being oxidized, the particle size and the mass ratio of nickel powder to nickel oxide powder are optimized; in addition, the invention discloses the conductive nickel oxide target material.

Description

Technical Field

[0001] The present application relates to the technical field of electrically permeable thin film production, and in particular to a conductive nickel oxide target material and a preparation method thereof. Background Art

[0002] At present, most solar cells are made of semiconductor materials, and photoelectrochemical cells are made of semiconductor materials and electrolytes. Regardless of the materials used, the semiconductor materials must have moderate energy bands, matching energy levels of each part, high photoelectric conversion efficiency, environmentally friendly raw materials, stable material properties, and be suitable for industrial mass production. Nickel oxide (NiO x ) is a typical p-type direct bandgap semiconductor material with a bandgap width of 3.15 to 4.0 eV. It has antiferromagnetism and is an inorganic compound. It is the most stable oxide of nickel metal. Due to its excellent electrical properties and chemical stability, it is one of the most promising functional materials.

[0003] NiO x The crystal structure is similar to that of sodium chloride, that is, the rock salt structure, with a lattice parameter of 0.417nm, in which the Ni atom is at the center, and each Ni atom is surrounded by 6 O atoms with similar distances to form an octahedron. The entire crystal can be regarded as a face-centered cubic arrangement, with Ni and O atoms in the same face-centered cubic arrangement interlaced; NiO x It has a special electronic structure. The 3d, 4s, and 4p orbitals of nickel atoms are not occupied. However, due to the interaction between electrons, the electrons in the 3d orbital of nickel atoms can only be bound to the nickel orbital. Therefore, at room temperature, NiO x Become an excellent insulator.

[0004] However, NiO x The stoichiometric ratio of the film is not always 1:1, due to the NiO x The presence of nickel vacancies in the film causes holes to concentrate on the nickel vacancies, thus showing a p-type semiconductor state. However, in the actual preparation of NiO x During the process, Ni vacancies with high ionization energy are likely to appear, making the undoped NiO x The hole density in nickel oxide is at a low level, which leads to a decrease in the concentration of carriers. Therefore, it is crucial to improve the conductive properties of nickel oxide.

[0005] Chinese patent application 202410542009.9 discloses a nickel zinc oxide target material and its preparation method and application. The main raw materials of the nickel zinc oxide target material provided by the scheme include nickel oxide and a certain proportion of dopants, wherein the dopant is zinc oxide. After nickel oxide is doped with zinc oxide, the conductivity of the material can be improved. Subsequently, the nickel zinc oxide target material can be further made into a thin film with high transmittance. Zinc oxide also has a sintering effect, which can increase the density of the target material. Moreover, compared with other metal oxides, zinc oxide has the characteristics of low price, stability, high purity and environmental protection. The nickel zinc oxide target material provided by the scheme has a relative density of 87.4~98.2%, and a resistivity as low as 2.7×10 4 ~3.5×10 6 Ω·cm. After these targets are made into thin films, the film transmittance can reach 78-84%, which is suitable for the hole transport layer of perovskite solar cells.

[0006] It can be seen from the above scheme that the above scheme improves the conductivity of nickel oxide by doping zinc oxide into nickel oxide.

[0007] Chinese patent application 202311106081.9 discloses a nickel oxide target material for perovskite and a perovskite battery, comprising the following steps:

[0008] Step 1, preparing nickel oxide powder particles;

[0009] Step 2: Plasma spraying nickel oxide powder particles onto a substrate material to obtain a target material;

[0010] In this scheme, nickel oxide is used as an electron transport layer in the perovskite structure to replace the commonly used tin oxide, titanium oxide, etc. Nickel oxide is stable in nature, but it is not conductive itself. By adding nickel oxide powder, it is made into an oxygen-depleted state in the previous preparation process, and pure nickel powder is added to further improve the conductivity. The final nickel oxide target material for perovskite has high density, low resistivity, and good conductivity, which improves the efficiency and stability of perovskite batteries. The conversion efficiency of the battery reaches 23.7%;

[0011] It can be seen that this scheme also uses pure nickel powder to improve the conductivity of nickel oxide, but observing the preparation method of this scheme, it can be seen that this scheme prepares the target material by plasma spraying rather than the traditional powder metallurgy method;

[0012] In traditional powder metallurgy methods, additives are usually needed to improve the bonding and dispersion between powders, and in the subsequent process, the organic additives in the target blank need to be removed by calcination and degumming in an oxygen atmosphere. The degumming process can easily cause oxidation of nickel powder, resulting in a decrease in the conductivity of the target material.

[0013] The problem that this solution needs to solve is: how to provide a method for preparing conductive nickel oxide target based on traditional powder metallurgy process. Summary of the invention

[0014] The purpose of the present application is to provide a method for preparing a conductive nickel oxide target material, which achieves its conductive ability by adding a certain amount of nickel powder to nickel oxide powder, and at the same time improves the density of the target material through an additive and removes the additive through a subsequent oxygen-containing calcination process. In addition, the present application optimizes the particle size and mass ratio of nickel powder and nickel oxide powder to prevent oxidation of nickel powder due to contact between oxygen and nickel powder during the calcination process, thereby further ensuring the conductive ability of the nickel oxide target material.

[0015] To achieve the above object, the present application discloses a method for preparing a conductive nickel oxide target, comprising the following steps:

[0016] Step 1: Mix nickel oxide powder, nickel powder, additives and pure water to obtain slurry;

[0017] Step 2: spray granulation, pre-pressing and calcining the slurry obtained in step 1 to obtain a nickel oxide blank;

[0018] Step 3: sintering the nickel oxide blank obtained in step 2 to obtain a conductive nickel oxide target;

[0019] The calcination process is completed in an oxygen atmosphere, and the calcination temperature is not higher than 400°C;

[0020] The particle size of nickel oxide powder is 100-150 μm, and the particle size of nickel powder is 50-75 μm;

[0021] The mass ratio of nickel oxide powder to nickel powder is 99-99.8:0.2-1.

[0022] Preferably, the auxiliary agent consists of a dispersant and a binder;

[0023] The dispersant is selected from at least one of polyacrylamide, polyethylene glycol, hydrogenated nitrile rubber, triethylhexyl phosphoric acid, sodium lauryl sulfate, and methyl amyl alcohol;

[0024] The binder is selected from at least one of butyl rubber, polyvinyl alcohol, cyanoacrylate, methacrylate, acrylic emulsion and carboxymethyl cellulose.

[0025] Preferably, the mass ratio of nickel oxide powder, nickel powder, dispersant, binder and pure water is 99-99.8:0.2-1:1:1:80-90.

[0026] Preferably, step 2 includes the following sub-steps:

[0027] Step A1: spray granulating the slurry obtained in step 1 to obtain powder;

[0028] Step A2: the powder obtained in step A1 is molded at a pressure of 20 to 30 MPa for 8 to 12 minutes, and then cold isostatically pressed at a pressure of 150 to 300 MPa for 2 to 4 minutes to obtain an intermediate;

[0029] Step A3: The intermediate obtained in step A2 is placed in an oxygen atmosphere and calcined at a temperature of 300-400° C. for 5-8 hours to obtain a nickel oxide blank.

[0030] Preferably, the sintering in step 3 specifically includes primary sintering and secondary sintering;

[0031] The primary sintering is specifically as follows: placing the nickel oxide blank obtained in step 2 under a pressure environment of 50 to 80 MPa and sintering at a temperature of 1000 to 1200° C. for 6 to 8 hours to obtain a primary sintering material;

[0032] The secondary sintering is specifically as follows: placing the primary sintering material in an air atmosphere at a temperature of 1350-1450° C. for 10-15 hours under normal pressure to obtain a conductive nickel oxide target.

[0033] Preferably, the particle size of the nickel oxide powder is 100-150 μm, the particle size of the nickel powder is 50-75 μm, and the particle size of the nickel oxide powder is twice that of the nickel powder.

[0034] In addition, the present application also discloses a conductive nickel oxide target material, which is prepared by the above-mentioned conductive nickel oxide target material preparation method.

[0035] Preferably, the relative density of the conductive nickel oxide target is not less than 96%, and the resistance is not higher than 20 mΩ.cm.

[0036] The beneficial effects of this application are:

[0037] The present application achieves the conductive ability of nickel oxide powder by adding a certain amount of nickel powder to the powder, and at the same time improves the density of the target material through the auxiliary agent and removes the auxiliary agent through the subsequent oxygen-containing calcination process. The present application optimizes the particle size and mass ratio of nickel powder and nickel oxide powder to prevent the contact of oxygen with nickel powder during the calcination process to cause oxidation of the nickel powder, thereby further ensuring the conductive ability of the nickel oxide target material. DETAILED DESCRIPTION

[0038] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. In the description of the present invention, it should be noted that, if no specific conditions are specified in the embodiments, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0039] Example 1

[0040] Step 1: nickel oxide powder, nickel powder, polyacrylamide, polyvinyl alcohol and pure water are mixed in a mass ratio of 99.5:0.5:1:1:85 to obtain a slurry, wherein the particle size of the nickel oxide powder is 120 μm, and the particle size of the nickel powder is 55 μm;

[0041] Step 2:

[0042] Step A1: spray granulating the slurry obtained in step 1 to obtain powder;

[0043] Step A2: The powder obtained in step A1 is molded at a pressure of 25 MPa for 10 min, and then cold isostatically pressed at 230 MPa for 3 min to obtain an intermediate;

[0044] Step A3: The intermediate obtained in step A2 is placed in an oxygen atmosphere and calcined at 350° C. for 6.5 hours to obtain a nickel oxide blank.

[0045] Step 3: placing the nickel oxide blank obtained in step 2 in a pressure environment of 65 MPa and sintering at a temperature of 1100° C. for 7 hours to obtain a primary sintered material;

[0046] The primary sintered material was sintered at 1400° C. for 13 hours under normal pressure and air atmosphere to obtain a conductive nickel oxide target.

[0047] Example 2

[0048] Step 1: nickel oxide powder, nickel powder, polyacrylamide, polyvinyl alcohol and pure water are mixed in a mass ratio of 99:1:1:1:80 to obtain a slurry, wherein the particle size of the nickel oxide powder is 100 μm and the particle size of the nickel powder is 75 μm;

[0049] Step 2:

[0050] Step A1: spray granulating the slurry obtained in step 1 to obtain powder;

[0051] Step A2: The powder obtained in step A1 is molded at a pressure of 20 MPa for 12 minutes, and then cold isostatically pressed at 150 MPa for 4 minutes to obtain an intermediate;

[0052] Step A3: The intermediate obtained in step A2 is placed in an oxygen atmosphere and calcined at 300° C. for 8 hours to obtain a nickel oxide blank.

[0053] Step 3: placing the nickel oxide blank obtained in step 2 in a pressure environment of 50 MPa and sintering at a temperature of 1000° C. for 8 hours to obtain a primary sintered material;

[0054] The primary sintered material was sintered at 1350° C. for 15 h under normal pressure and air atmosphere to obtain a conductive nickel oxide target.

[0055] Example 3

[0056] Step 1: nickel oxide powder, nickel powder, polyacrylamide, polyvinyl alcohol and pure water are mixed in a mass ratio of 99.8:0.2:1:1:90 to obtain a slurry, wherein the particle size of the nickel oxide powder is 150 μm and the particle size of the nickel powder is 50 μm;

[0057] Step 2:

[0058] Step A1: spray granulating the slurry obtained in step 1 to obtain powder;

[0059] Step A2: The powder obtained in step A1 is molded at a pressure of 30 MPa for 8 minutes, and then cold isostatically pressed at 300 MPa for 2 minutes to obtain an intermediate;

[0060] Step A3: The intermediate obtained in step A2 is placed in an oxygen atmosphere and calcined at 400° C. for 5 hours to obtain a nickel oxide blank.

[0061] Step 3: placing the nickel oxide blank obtained in step 2 in a pressure environment of 50 MPa and sintering at a temperature of 1200° C. for 6 hours to obtain a primary sintered material;

[0062] The primary sintered material was sintered at 1450° C. for 10 hours under normal pressure and air atmosphere to obtain a conductive nickel oxide target.

[0063] Example 4

[0064] It is basically the same as Example 1, except that the particle size of the nickel oxide powder is 120 μm, and the particle size of the nickel powder is 70 μm.

[0065] Example 5

[0066] It is basically the same as Example 1, except that the particle size of the nickel oxide powder is 120 μm, and the particle size of the nickel powder is 60 μm.

[0067] Example 6

[0068] The method is basically the same as Example 1, except that a mixture of polyacrylamide and polyethylene glycol is used to replace polyacrylamide, and the mass ratio of polyacrylamide to polyethylene glycol is 1:1.

[0069] Example 7

[0070] The method is basically the same as Example 1, except that polyethylene glycol is used to replace polyacrylamide.

[0071] Comparative Example 1

[0072] Step 1: nickel oxide powder, nickel powder, polyacrylamide, polyvinyl alcohol and pure water are mixed in a mass ratio of 99.5:0.5:1:1:85 to obtain a slurry, wherein the particle size of the nickel oxide powder is 120 μm, and the particle size of the nickel powder is 55 μm;

[0073] Step 2:

[0074] Step A1: spray granulating the slurry obtained in step 1 to obtain powder;

[0075] Step A2: The powder obtained in step A1 is molded at a pressure of 25 MPa for 10 min, and then cold isostatically pressed at 230 MPa for 3 min to obtain an intermediate;

[0076] Step 3: placing the nickel oxide blank obtained in step 2 in a pressure environment of 65 MPa and sintering at a temperature of 1100° C. for 7 hours to obtain a primary sintered material;

[0077] The primary sintered material was sintered at 1400° C. for 13 hours under normal pressure and air atmosphere to obtain a conductive nickel oxide target.

[0078] Comparative Example 2

[0079] Step 1: nickel oxide powder, nickel powder and pure water are mixed in a mass ratio of 99.5:0.5:85 to obtain a slurry, wherein the particle size of the nickel oxide powder is 120 μm and the particle size of the nickel powder is 55 μm;

[0080] Step 2:

[0081] Step A1: spray granulating the slurry obtained in step 1 to obtain powder;

[0082] Step A2: The powder obtained in step A1 is molded at a pressure of 25 MPa for 10 min, and then cold isostatically pressed at 230 MPa for 3 min to obtain an intermediate;

[0083] Step 3: placing the nickel oxide blank obtained in step 2 in a pressure environment of 65 MPa and sintering at a temperature of 1100° C. for 7 hours to obtain a primary sintered material;

[0084] The primary sintered material was sintered at 1400° C. for 13 hours under normal pressure and air atmosphere to obtain a conductive nickel oxide target.

[0085] Comparative Example 3

[0086] It is basically the same as Example 1, except that the particle size of the nickel oxide powder is 200 μm, and the particle size of the nickel powder is 40 μm.

[0087] Comparative Example 4

[0088] It is basically the same as Example 1, except that the particle size of the nickel oxide powder is 100 μm and the particle size of the nickel powder is 100 μm.

[0089] Comparative Example 5

[0090] The method is basically the same as Example 1, except that the mass ratio of nickel oxide powder to nickel powder is 95:5.

[0091] Comparative Example 6

[0092] The method is basically the same as Example 1, except that the mass ratio of nickel oxide powder to nickel powder is 99.9:0.1.

[0093] Comparative Example 7

[0094] The method is basically the same as Example 1, except that step A3 specifically comprises: calcining the intermediate obtained in step A2 at 600° C. in an oxygen atmosphere for 8 hours to obtain a nickel oxide blank.

[0095] Performance Test:

[0096] The relative density of the target material was tested using the Archimedes drainage method;

[0097] The resistivity of the target material was tested using the four-point probe method;

[0098] The above test results are shown in Table 1:

[0099] Table 1

[0100]

[0101]

[0102] Result analysis:

[0103] 1. It can be seen from Examples 1-3 that when the process parameters in the preparation process of nickel oxide target materials are slightly adjusted, the relative density and resistivity of Examples 1-3 show certain fluctuations, but the fluctuation range is relatively small;

[0104] 2. It can be seen from Example 1 and Examples 4-5 that when the particle size of the nickel oxide powder in Example 5 is 2:1 to the particle size of the nickel powder, the relative density and conductivity of Example 5 show a more obvious downward trend relative to Example 1 and Example 4. It can be seen that at this particle size, the distribution of nickel in the nickel oxide in the target material prepared in Example 5 is more uniform, thereby improving the density of the target material and the mobility of carriers in the target material;

[0105] 3. It can be seen from Example 1 and Examples 6-7 that when Example 6 mixes the dispersants polyacrylamide and polyethylene glycol, the resistivity of the target material prepared in Example 6 decreases slightly compared with that in Example 1 and Example 7. It can be seen that Example 6 improves the dispersion of nickel in nickel oxide through the combined action of the two dispersants;

[0106] It is not difficult to infer from Examples 4-5 that increasing the dispersion of nickel in nickel oxide can improve the conductivity of the target material;

[0107] At the same time, the relative density data of Example 6 shows that improving the dispersion degree may not necessarily improve the relative density of the target material. It can be seen that the reason for the increase in the density of the target material in Example 5 is more likely to come from the particle size itself;

[0108] 4. It can be seen from Example 1 and Comparative Example 1 that when step A3, i.e., the degumming step of calcining in air atmosphere, is omitted, the resistivity of Comparative Example 1 is significantly improved relative to that of Example 1. It can be seen that not performing degumming is not conducive to the conductivity of the target material;

[0109] Further observation of Comparative Example 2 shows that when we omit the use of the additive, although there is no need to consider the subsequent degumming step, the resistivity of Comparative Example 2 is still significantly improved compared with Example 1. At the same time, with the omission of the additive, the nickel oxide and nickel in the target material may cause component segregation due to their own weight, thereby causing a significant decrease in relative density;

[0110] 5. It can be seen from Example 1 and Comparative Examples 3-4 that when the particle size difference between nickel oxide and nickel is too large or too small, the conductivity and relative density of Comparative Examples 3-4 show a significant downward trend;

[0111] When the amount of nickel powder added is changed in Comparative Examples 5-6, although the carrier concentration increases and the resistivity decreases in Comparative Example 5 due to the increase in the amount of nickel powder added, the excessively high nickel content in the nickel oxide target will undoubtedly increase the difficulty of the subsequent coating process. The reason is that in the coating process, a pure nickel oxide film is more desired, and elemental nickel is regarded as an impurity. When the mass of elemental nickel is relatively small, we can change the gas environment in the coating process and use a small amount of oxidizing gas to oxidize elemental nickel. However, if the elemental nickel content is too high, it is necessary to increase the oxygen concentration in the subsequent coating process, and an excessively high increase in oxygen concentration may have an impact on the film and substrate materials.

[0112] 6. It can be seen from Example 1 and Comparative Example 7 that during the degumming process in Step A3, excessively high calcination temperature may cause oxidation of nickel powder in the nickel oxide target, thereby significantly improving the conductivity of the nickel oxide target.

[0113] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a conductive nickel oxide target, characterized in that: The following steps are involved: Step 1: Mix nickel oxide powder, nickel powder, additives and pure water to obtain slurry; Step 2: spray granulation, pre-pressing and calcining the slurry obtained in step 1 to obtain a nickel oxide blank; Step 3: sintering the nickel oxide blank obtained in step 2 to obtain a conductive nickel oxide target; The calcination process is completed in an oxygen atmosphere, and the calcination temperature is not higher than 400°C; The particle size of the nickel oxide powder is 100 to 150 μm, and the particle size of the nickel powder is 50 to 75 μm; The mass ratio of nickel oxide powder to nickel powder is 99-99.8:0.2-1.

2. The method for preparing a conductive nickel oxide target according to claim 1, characterized in that: The auxiliary agent is composed of a dispersant and a binder; The dispersant is selected from at least one of polyacrylamide, polyethylene glycol, hydrogenated nitrile rubber, triethylhexyl phosphoric acid, sodium lauryl sulfate, and methyl amyl alcohol; The binder is selected from at least one of butyl rubber, polyvinyl alcohol, cyanoacrylate, methacrylate, acrylic emulsion, and carboxymethyl cellulose.

3. The method for preparing a conductive nickel oxide target according to claim 2, characterized in that: The mass ratio of the nickel oxide powder, nickel powder, dispersant, binder and pure water is 99-99.8:0.2-1:1:1:80-90.

4. The method for preparing a conductive nickel oxide target according to claim 1, characterized in that: The step 2 includes the following sub-steps: Step A1: spray granulating the slurry obtained in step 1 to obtain powder; Step A2: the powder obtained in step A1 is molded at a pressure of 20 to 30 MPa for 8 to 12 minutes, and then cold isostatically pressed at a pressure of 150 to 300 MPa for 2 to 4 minutes to obtain an intermediate; Step A3: The intermediate obtained in step A2 is placed in an oxygen atmosphere and calcined at a temperature of 300-400° C. for 5-8 hours to obtain a nickel oxide blank.

5. The method for preparing a conductive nickel oxide target according to claim 1, characterized in that: The sintering in step 3 specifically includes primary sintering and secondary sintering; The primary sintering is specifically as follows: placing the nickel oxide blank obtained in step 2 under a pressure environment of 50 to 80 MPa and sintering at a temperature of 1000 to 1200° C. for 6 to 8 hours to obtain a primary sintering material; The secondary sintering is specifically as follows: placing the primary sintering material under normal pressure and air atmosphere at a temperature of 1350-1450° C. for 10-15 hours to obtain a conductive nickel oxide target.

6. The method for preparing a conductive nickel oxide target according to claim 1, characterized in that: The particle size of the nickel oxide powder is 100-150 μm, the particle size of the nickel powder is 50-75 μm, and the particle size of the nickel oxide powder is twice that of the nickel powder.

7. A conductive nickel oxide target, characterized in that: The target is prepared by the method for preparing a conductive nickel oxide target as described in any one of claims 1 to 6.

8. The conductive nickel oxide target according to claim 7, characterized in that: The relative density of the conductive nickel oxide target material is not less than 96%, and the resistance is not higher than 20 mΩ.cm.

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