High work function metal oxide target and method of making same

Abstract

The application discloses a high work function metal oxide target material and a preparation method thereof. The preparation method comprises the following steps: mixing high work function metal oxide powder, indium oxide powder and zinc oxide powder into mixed powder according to a set mass ratio; setting the mixed powder in deionized water, adding a dispersing agent, and modulating the mixed powder into slurry; performing high-energy sand milling on the slurry, and adding a binder before the sand milling is completed; performing spray granulation on the slurry to obtain spherical granulation powder; performing die pressing and cold isostatic pressing on the spherical granulation powder to obtain a target material blank; and performing debinding and sintering integrated treatment on the target material blank to obtain the high work function metal oxide target material. The high work function metal oxide target material disclosed in the embodiment of the application has small grain size, uniform distribution, high target material density and excellent electrical performance, and can be used for preparing a flexible OLED anode layer thin film material, simplifying a device structure and reducing cost and increasing efficiency.

Description

Technical Field

[0001] This invention belongs to the field of sputtering target technology, specifically relating to high work function metal oxide targets and their preparation methods. Background Technology

[0002] With the rapid development of today's digital society, people have an increasing demand for high refresh rate, high resolution, and low power consumption flat panel displays. Among them, organic light-emitting diodes (OLEDs) have the characteristics of high efficiency, high brightness, wide viewing angle, low power consumption, self-illumination, low driving voltage, fast response speed, full color, can be made into ultra-thin and large-area displays, lightweight materials, flexibility and easy processing, and strong applicability, which can meet the requirements of today's display devices for higher performance and larger information capacity.

[0003] In OLED devices, the most commonly used anode thin film material is ITO, with a work function (WF) of around -4.7 eV. However, the highest occupied molecular orbital (HOMO) energy level of the organic hole transport layer is typically around -5.7 eV. This mismatch between the work function of ITO and the HOMO energy level of the organic layer leads to a decrease in hole injection efficiency, which in turn affects the device's turn-on voltage and overall power consumption. To address this issue, a hole injection layer (HIL) is typically added between the anode and the organic hole transport layer. This HIL has a HOMO energy level of approximately -5.2 eV, which better matches the energy levels of the anode and the organic layer, thereby improving hole injection efficiency. However, this method not only increases the fabrication process of OLED devices but also raises costs. Therefore, there is an urgent need to develop transition metal oxide anode materials with high work function, high transmittance, and high conductivity to achieve cost reduction and efficiency improvement. Summary of the Invention

[0004] In view of this, some embodiments disclose a method for preparing a high work function metal oxide target, including:

[0005] High work function metal oxide powder, indium oxide powder, and zinc oxide powder are mixed in a set mass ratio to form a mixed powder.

[0006] The mixed powder is placed in deionized water and a dispersant is added to prepare a slurry;

[0007] The slurry is subjected to high-energy sand milling, and a binder is added before the sand milling is completed;

[0008] The slurry is spray-granulated to obtain spherical granulated powder;

[0009] The spherical granulated powder is molded and cold isostatically pressed to obtain the target material preform;

[0010] The target blank is degreased and sintered in one process to obtain a high work function metal oxide target.

[0011] The integrated degreasing and sintering process specifically includes:

[0012] The target blank is placed in an integrated degreasing and sintering furnace, heated to the degreasing temperature of 450-650℃, with a heating rate of 0.5-1℃ / min, and held for 6-12 hours. The degreasing atmosphere is air, with an air flow rate of 3-12L / min.

[0013] The temperature is increased from the degreasing temperature to the first step temperature of 900-1100℃ at a rate of 0.5-3℃ / min, and held for 6-12 hours. The sintering atmosphere is oxygen with an oxygen flow rate of 3-12L / min.

[0014] The temperature is increased from the first step temperature to the second step temperature of 1450-1550℃ at a rate of 3-5℃ / min, without heat preservation.

[0015] The temperature is lowered from the second-stage temperature to the third-stage sintering temperature of 1150–1400℃ at a rate of 10–20℃ / min, and held for 12–36 hours.

[0016] The temperature is lowered from the third-stage temperature to the fourth-stage temperature of 600-800℃ at a rate of 1-3℃ / min, and held for 3-6 hours. The sintering atmosphere is adjusted to air with an air flow rate of 3-12L / min.

[0017] The temperature is lowered from the fourth step temperature to 200℃ at a rate of 3–10℃ / min, and then allowed to cool naturally to room temperature.

[0018] Some embodiments disclose a method for preparing high work function metal oxide targets, wherein the purity of the high work function metal oxide powder, indium oxide powder, and zinc oxide powder is not less than 99.99%, and the particle size is 100-1000 nm.

[0019] In some embodiments, the method for preparing high work function metal oxide targets discloses a method in which the mass ratio of zinc oxide powder to indium oxide powder is 10-20:80-90; and the mass ratio of the high work function metal oxide powder to the total mass of zinc oxide powder and indium oxide powder is 2-10:90-98.

[0020] Some embodiments disclose a method for preparing high work function metal oxide targets, wherein the high work function metal oxide powder is MoO3, CoO, WO3, NiO or TiO2.

[0021] Some embodiments disclose a method for preparing high work function metal oxide targets, wherein the mass of deionized water is 60-90% of the total mass of the mixed powder, the mass of dispersant is 0.5-1.5% of the total mass of the mixed powder, the mass of binder is 0.5-2% of the total mass of the mixed powder, and the viscosity of the slurry is 35-45 mPa·s.

[0022] Some embodiments disclose a method for preparing high work function metal oxide targets, wherein the ball-to-material ratio of high-energy sand milling is 1 to 5:1, and the time is 20 to 80 minutes.

[0023] Some embodiments disclose a method for preparing high work function metal oxide targets, in which slurry spray granulation is carried out in a granulator with an inlet air temperature of 200-300°C, an exhaust air temperature of 80-100°C, and a frequency of 30-50Hz.

[0024] Some embodiments disclose a method for preparing high work function metal oxide targets, wherein the molding pressure is 30-80 MPa and the cold isostatic pressing pressure is 200-350 MPa.

[0025] Some embodiments disclose a method for preparing high work function metal oxide targets, wherein the relative density of the target blank is not less than 60%.

[0026] Some embodiments disclose high work function metal oxide targets, which are obtained by the above-described high work function metal oxide target preparation method; the high work function metal oxide target has a relative density of not less than 99.5%, a resistivity of 0.2 to 6 mΩ·cm, and a work function of 5.0 to 6.5 eV.

[0027] The method for preparing high work function metal oxide targets disclosed in this invention uses IZO with high transmittance and high conductivity as the main component, adds high work function metal oxides, and uses a spray granulation process to obtain a mixed powder with uniform size distribution. A debinding and sintering integrated processing method is used, combined with a multi-step variable temperature sintering process, to sinter the target blank under a set oxygen flow rate. This suppresses abnormal grain growth, facilitates grain refinement, reduces oxygen vacancies, and improves the density of the target material, ultimately resulting in a high work function metal oxide target with uniform and refined microstructure. The high work function metal oxide target disclosed in this invention has small, uniformly distributed grain size, high target density, and excellent electrical properties. It can be used to prepare flexible OLED anode layer thin film materials, simplifying device structure and reducing costs while increasing efficiency. Attached Figure Description

[0028] Figure 1 Example 1: SEM image of Mo-IZO spherical granulated powder;

[0029] Figure 2 Example 1: Phase structure diagram of Mo-IZO target material. Detailed Implementation

[0030] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0031] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0032] The terms “basic” and “approximately” used in this document are to describe small fluctuations. For example, they can mean less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data presented or expressed in range format in this document are used for convenience and brevity only, and should therefore be flexibly interpreted to include not only the explicitly listed values ​​that define the range, but also all independent values ​​or subranges contained within that range. For example, a numerical range of “1–5%” should be interpreted to include not only the explicitly listed values ​​from 1% to 5%, but also the independent values ​​and subranges within the indicated range. Thus, this numerical range includes independent values ​​such as 2%, 3.5%, and 4%, and subranges such as 1%–3%, 2%–4%, and 3%–5%, etc. This principle also applies to ranges that list only one value. Furthermore, this interpretation applies regardless of the width of the range or the characteristics described.

[0033] In this document, including in the claims, conjunctions such as "comprising," "including," "with," "having," "containing," "involving," and "accommodating" are understood to be open-ended, meaning "including but not limited to." Only the conjunctions "consisting of" and "composed of" are closed conjunctions.

[0034] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0035] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solutions belong to the content disclosed in the embodiments of this application. It should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" used in this application indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing technical features and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention unless they conflict with the context. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance unless they conflict with the context.

[0036] In some embodiments, the preparation method of high work function metal oxide targets includes:

[0037] High work function metal oxide powder, indium oxide powder, and zinc oxide powder are mixed in a set mass ratio to form a mixed powder. Generally, the purity of the high work function metal oxide powder, indium oxide powder, and zinc oxide powder is not less than 99.99%, and the particle size is 100-1000 nm. The mass ratio of zinc oxide powder to indium oxide powder is 10-20:80-90. The mass ratio of high work function metal oxide powder to the total mass of zinc oxide powder and indium oxide powder is 2-10:90-98. By controlling the mass ratio of indium oxide to zinc oxide, the density and conductivity of the high work function metal oxide target material are guaranteed.

[0038] The mixed powder is placed in deionized water, and a dispersant is added to prepare a slurry. Generally, the mass of deionized water is 60-90% of the total mass of the mixed powder, the mass of the dispersant is 0.5-1.5% of the total mass of the mixed powder, the mass of the binder is 0.5-2% of the total mass of the mixed powder, and the viscosity of the slurry is 35-45 mPa·s. The content of deionized water needs to be strictly controlled to ensure that the slurry has an appropriate solid content and that the viscosity of the slurry is within a suitable range, which is beneficial for obtaining a mixed powder slurry with a narrow particle size distribution through ball milling. The dispersant helps the mixed powder disperse in deionized water and can improve the ball milling effect of the slurry.

[0039] The slurry is subjected to high-energy sand milling, and a binder is added before the sand milling is completed. The binder increases the viscosity of the slurry, connects the particles in the slurry, improves the granulation performance of the slurry, and ensures that the slurry has a high sphericity after spray granulation, which is beneficial to the subsequent green body forming. Generally, the binder is added about ten minutes before the sand milling is completed. The binder is a colloidal aqueous solution of polyvinyl alcohol with a concentration of 8-15%. Generally, the dispersant and binder can be completely removed in the subsequent debinding and sintering process without affecting the sintering performance of the high work function metal oxide target.

[0040] The slurry is spray-granulated to obtain spherical granulated powder. The spherical granulated powder has high dryness, high sphericity, and uniform particle size distribution. In the subsequent debinding and sintering process, it can improve sintering activity and reduce sintering temperature.

[0041] The spherical granulated powder is molded and then cold isostatically pressed to obtain a target blank; generally, the molding pressure is 30-80 MPa, and the cold isostatic pressing pressure is 200-350 MPa; the relative density of the target blank is not less than 60%;

[0042] The target blank is degreased and sintered in one process to obtain a high work function metal oxide target.

[0043] The integrated degreasing and sintering process specifically includes:

[0044] The target blank is placed in an integrated debinding and sintering furnace and heated to the debinding temperature of 450–650℃ at a heating rate of 0.5–1℃ / min. It is held for 6–12 hours. The debinding atmosphere is air with a flow rate of 3–12 L / min. The air atmosphere can absorb and expel lipid gases. The air flow during the debinding stage can better remove the high molecular weight substances in the dispersant and binder. Holding at a certain temperature can make the lipids volatilize from the blank and prevent them from affecting the further densification of the target material.

[0045] The temperature is increased from the degreasing temperature to the first step temperature of 900–1100℃ at a rate of 0.5–3℃ / min, and held for 6–12 hours. The sintering atmosphere is oxygen, with an oxygen flow rate of 3–12 L / min. Generally, the holding time at the first step temperature should not exceed 25 hours to prevent grain size growth due to excessive holding time. The first step holding temperature is set within the phase transformation temperature range of the target blank to ensure complete phase transformation and initial shrinkage of the target blank.

[0046] The temperature is increased from the first step temperature to the second step temperature of 1450-1550℃ at a rate of 3-5℃ / min, without heat preservation. The second temperature step is the highest temperature point, without heat preservation. It is generally set according to the material system and is 50-200℃ higher than the third step temperature. This is to reach the driving temperature for grain growth in the target material blank, stimulate grain growth, and accelerate the densification rate.

[0047] The temperature is lowered from the second-stage temperature to the third-stage sintering temperature of 1150-1400℃ at a rate of 10-20℃ / min, and held for 12-36 hours. The third temperature stage is the long-term holding temperature, which is set to the temperature at which the shrinkage rate of the target material blank is the largest. During this stage, the pores of grain growth are closed, and the densification process is greatly accelerated.

[0048] The temperature is lowered from the third-stage temperature to the fourth-stage temperature of 600–800℃ at a rate of 1–3℃ / min, and held for 3–6 hours. The sintering atmosphere is adjusted to air with a flow rate of 3–12 L / min. The fourth-stage temperature is to prevent the sample from cracking at a lower temperature due to excessively rapid cooling. Since the fourth-stage temperature is significantly lower, and the oxygen atmosphere mainly functions at high temperatures to prevent the oxides from decomposing at high temperatures, the oxygen atmosphere is adjusted to an air atmosphere at this point to reduce costs.

[0049] The temperature is lowered from the fourth step temperature to 200℃ at a rate of 3–10℃ / min, and then allowed to cool naturally to room temperature.

[0050] Typically, the sintering process is carried out in an oxygen atmosphere because zinc oxide and indium oxide volatilize to varying degrees at high temperatures, which is detrimental to the stability of the target material composition and the density of the target material. The sintering heating rate should not be too fast or too slow. If the heating rate is too fast, the target material blank will be heated unevenly and cannot react completely, causing the target material to crack. If the heating rate is too slow, the sintering time will be too long, which is not conducive to production.

[0051] Typically, the sintering temperature should not exceed 1600℃. Indium oxide decomposes too quickly at temperatures above 1600℃, which is not conducive to obtaining target materials with high crystallinity, high purity, and uniform morphology.

[0052] In some embodiments, the high work function metal oxide powder is MoO3, CoO, WO3, NiO, or TiO2.

[0053] In some embodiments, the ball-to-particle ratio in the high-energy sand mill is 1–5:1, and the time is 20–80 min. Generally, the slurry is placed in a high-energy sand mill and milled using zirconia grinding balls with a diameter of 1 mm. During the high-energy sand milling process, the mixed powder particles in the slurry are pulverized, the particle size is reduced, and nanoparticles with a small and uniform particle size distribution are formed, which is beneficial for subsequent granulation processes. The metal oxide powder in the slurry is milled efficiently in the high-energy sand mill, resulting in refined particle size, which effectively increases the sintering activity of the powder.

[0054] In some embodiments, the slurry is circulated multiple times within a sand mill to obtain a slurry with a solid content of approximately 50-70%.

[0055] In some embodiments, the slurry after sand milling is left to stand and age for a period of time to allow the grains to grow fully. The grain growth time is generally more than half an hour, preferably more than two hours.

[0056] In some embodiments, the rotational speed of the high-energy sand mill is set to 300–600 r / min.

[0057] In some embodiments, the slurry spray granulation is carried out in a granulator with an inlet air temperature of 200-300°C, an exhaust air temperature of 80-100°C, and a frequency of 30-50Hz, resulting in granulated powder with a particle size of approximately 200-300nm.

[0058] In some embodiments, the high work function metal oxide target is obtained by the above-described preparation method of the high work function metal oxide target; the high work function metal oxide target has a relative density of not less than 99.5%, a resistivity of 0.2 to 6 mΩ·cm, and a work function of 5.0 to 6.5 eV.

[0059] The technical details are further illustrated below with reference to the embodiments.

[0060] Example 1

[0061] Figure 1 Here is a SEM image of the Mo-IZO spherical granulated powder disclosed in Example 1; Figure 2 This is a phase structure diagram of the Mo-IZO target material disclosed in Example 1.

[0062] Example 1 discloses a method for preparing a high work function metal oxide target, comprising:

[0063] 427.5g of ZnO powder, 712.5g of In2O3 powder and 60g of MoO3 powder were mixed to form a mixed powder; the mass ratio of In2O3 to ZnO was 62.5:37.5, and the mass ratio of MoO3 to In2O3-ZnO was 5:95.

[0064] The mixed powder was placed in 720g of deionized water and 12g of dispersant was added to prepare a slurry; the solid content of the slurry was 62.5% and the viscosity was 40mPa·s.

[0065] The slurry was high-energy milled for 60 minutes, with 12g of binder added 10 minutes before the end of milling to ensure thorough mixing and particle refinement of MoO3, In2O3, and ZnO. The slurry was then spray-granulated in a granulator with an inlet air temperature of 200℃, an outlet air temperature of 80℃, and a frequency of 30Hz, yielding 984g of spherical Mo-IZO granulated powder, with a powder yield of approximately 82%. Figure 1 As shown, Mo-IZO granulated powder exhibits good spheroidization, uniform particle size distribution, and no powder agglomeration;

[0066] The spherical granulated powder is molded and then subjected to cold isostatic pressing to obtain a target blank with a relative density of approximately 63%; wherein the molding pressure is 30 MPa and the cold isostatic pressing pressure is 250 MPa.

[0067] The target material preform undergoes an integrated debinding and sintering process, specifically including:

[0068] The target blank was placed in an integrated degreasing and sintering furnace, heated to the degreasing temperature of 600℃ at a heating rate of 0.5℃ / min, and held for 12 hours. The degreasing atmosphere was air with an air flow rate of 6L / min.

[0069] The temperature was increased from the degreasing temperature to the first step temperature of 1000℃ at a rate of 3℃ / min, and held for 10 hours. The sintering atmosphere was oxygen with an oxygen flow rate of 6L / min.

[0070] The temperature is increased from the first step temperature to the second step temperature of 1450℃ at a rate of 3℃ / min, without heat preservation;

[0071] The temperature was lowered from the second-stage temperature to the third-stage sintering temperature of 1350℃ at a rate of 20℃ / min, and held for 20 hours.

[0072] The temperature was lowered from the third step temperature to the fourth step temperature of 800℃ at a rate of 3℃ / min, and held for 3 hours. The sintering atmosphere was adjusted to air with an air flow rate of 6L / min.

[0073] The temperature is reduced from the fourth step temperature to 200℃ at a rate of 5℃ / min, and then allowed to cool naturally to room temperature.

[0074] A Mo-IZO target material was obtained with a relative density of 99.8%, a resistivity of 0.80 mΩ·cm, and a work function of 5.8 eV; Figure 2 As shown, the Mo-IZO target material has small and uniform grain size, no obvious pores, and high density.

[0075] Example 2

[0076] Example 2 discloses a method for preparing a high work function metal oxide target. Referring to Example 1, 450g of ZnO powder, 690g of In2O3 powder, and 96g of MoO3 powder were weighed, with a mass ratio of MoO3 to In2O3-ZnO of 8:92. 960g of spherical Mo-IZO granulated powder was obtained, with a powder yield of approximately 80%. The relative density of the obtained target blank was 63%. The relative density of the obtained Mo-IZO target was 99.6%, the resistivity was 0.42mΩ·cm, and the work function was 6.0eV.

[0077] Example 3

[0078] Example 3 discloses a method for preparing a high work function metal oxide target. Referring to Example 1, MoO3 powder is replaced with WO3 powder, 427.5g of ZnO powder, 712.5g of In2O3 powder, and 90g of WO3 powder are weighed, with a mass ratio of WO3 to In2O3-ZnO of 5:95. The resulting spherical W-IZO granulated powder has a powder yield of approximately 85%. The relative density of the obtained target blank is 61%. The relative density of the obtained W-IZO target is 99.6%, the resistivity is 5.0 mΩ·cm, and the work function is 5.2 eV.

[0079] Example 4

[0080] Example 4 discloses a method for preparing a high work function metal oxide target. Referring to Example 3, 450g of ZnO powder, 690g of In2O3 powder, and 96g of WO3 powder were weighed, with a mass ratio of WO3 to In2O3-ZnO of 8:92. The resulting spherical W-IZO granulated powder had a powder yield of approximately 86%. The relative density of the obtained target blank was 63%. The relative density of the obtained W-IZO target was 99.6%, the resistivity was 3.0 mΩ·cm, and the work function was 5.3 eV.

[0081] Example 5

[0082] Example 5 discloses a method for preparing a high work function metal oxide target. Referring to Example 1, MoO3 powder is replaced with TiO2 powder, 427.5g of ZnO powder, 712.5g of In2O3 powder, and 90g of TiO2 powder are weighed, with a mass ratio of TiO2 to In2O3-ZnO of 5:95. The resulting spherical Ti-IZO granulated powder has a powder yield of approximately 86%. The relative density of the obtained target blank is 61%. The relative density of the obtained Ti-IZO target is 99.5%, the resistivity is 5.2mΩ·cm, and the work function is 5.5eV.

[0083] Example 6

[0084] Example 6 discloses a method for preparing a high work function metal oxide target. Referring to Example 5, 450g of ZnO powder, 690g of In2O3 powder, and 96g of TiO2 powder were weighed, with a mass ratio of TiO2 to In2O3-ZnO of 8:92. The resulting spherical Ti-IZO granulated powder had a powder yield of approximately 85%. The relative density of the obtained target blank was 62%. The relative density of the obtained Ti-IZO target was 99.8%, the resistivity was 3.2mΩ·cm, and the work function was 5.7eV.

[0085] The method for preparing high work function metal oxide targets disclosed in this invention uses IZO with high transmittance and high conductivity as the main component, adds high work function metal oxides, and uses a spray granulation process to obtain a mixed powder with uniform size distribution. A debinding and sintering integrated processing method is used, combined with a multi-step variable temperature sintering process, to sinter the target blank under a set oxygen flow rate. This suppresses abnormal grain growth, facilitates grain refinement, reduces oxygen vacancies, and improves the density of the target material, ultimately resulting in a high work function metal oxide target with uniform and refined microstructure. The high work function metal oxide target disclosed in this invention has small, uniformly distributed grain size, high target density, and excellent electrical properties. It can be used to prepare flexible OLED anode layer thin film materials, simplifying device structure and reducing costs while increasing efficiency.

[0086] The technical solutions and technical details disclosed in the embodiments of this invention are merely illustrative of the inventive concept of this invention and do not constitute a limitation on the technical solutions of this invention. Any conventional changes, substitutions, or combinations made to the technical details disclosed in the embodiments of this invention have the same inventive concept as this invention and are within the protection scope of the claims of this invention.

Claims

1. A method for preparing a high work function metal oxide target, characterized in that, include: A high work function metal oxide powder, indium oxide powder, and zinc oxide powder are mixed in a predetermined mass ratio to form a mixed powder; wherein the mass ratio of zinc oxide powder to indium oxide powder is 10-20:80-90; the mass ratio of the high work function metal oxide powder to the total mass of zinc oxide powder and indium oxide powder is 2-10:90-98; and the high work function metal oxide powder is MoO3, CoO, WO3, or NiO. The mixed powder is placed in deionized water and a dispersant is added to prepare a slurry; wherein the mass of the deionized water is 60-90% of the total mass of the mixed powder, the mass of the dispersant is 0.5-1.5% of the total mass of the mixed powder, and the viscosity of the slurry is 35-45 mPa·s; The slurry is subjected to high-energy sand milling, and a binder is added before the sand milling is completed; the mass of the binder is 0.5% to 2% of the total mass of the mixed powder; The slurry is spray-granulated to obtain spherical granulated powder; The spherical granulated powder is molded and then cold isostatically pressed to obtain a target material preform; wherein the molding pressure is 30-80 MPa, and the cold isostatic pressing pressure is 200-350 MPa; the relative density of the target material preform is not less than 60%; The target blank is degreased and sintered in one process to obtain a high work function metal oxide target. Specifically, the integrated degreasing and sintering process includes: The target blank is placed in an integrated degreasing and sintering furnace, heated to the degreasing temperature of 450-650℃, with a heating rate of 0.5-1℃ / min, and held for 6-12 hours. The degreasing atmosphere is air, with an air flow rate of 3-12L / min. The temperature is increased from the degreasing temperature to the first step temperature of 900-1100℃ at a rate of 0.5-3℃ / min, and held for 6-12 hours. The sintering atmosphere is oxygen with an oxygen flow rate of 3-12L / min. The temperature is increased from the first step temperature to the second step temperature of 1450-1550℃ at a rate of 3-5℃ / min, without heat preservation. The temperature is lowered from the second-stage temperature to the third-stage sintering temperature of 1150–1400℃ at a rate of 10–20℃ / min, and held for 12–36 hours. The temperature is lowered from the third-stage temperature to the fourth-stage temperature of 600-800℃ at a rate of 1-3℃ / min, and held for 3-6 hours. The sintering atmosphere is adjusted to air with an air flow rate of 3-12L / min. The temperature is lowered from the fourth step temperature to 200℃ at a rate of 3–10℃ / min, and then allowed to cool naturally to room temperature.

2. The method for preparing a high work function metal oxide target according to claim 1, characterized in that, The high work function metal oxide powder, the indium oxide powder, and the zinc oxide powder have a purity of not less than 99.99% and a particle size of 100–1000 nm.

3. The method for preparing a high work function metal oxide target according to claim 1, characterized in that, The ball-to-material ratio of the high-energy sand mill is 1 to 5:1, and the time is 20 to 80 minutes.

4. The method for preparing a high work function metal oxide target according to claim 1, characterized in that, The slurry spray granulation is carried out in a granulator with an inlet air temperature of 200-300℃, an exhaust air temperature of 80-100℃, and a frequency of 30-50Hz.

5. A high work function metal oxide target, characterized in that, The high work function metal oxide target is obtained by the preparation method of any one of claims 1 to 4; the high work function metal oxide target has a relative density of not less than 99.5%, a resistivity of 0.2 to 6 mΩ·cm, and a work function of 5.0 to 6.5 eV.

Images