High-work-function metal oxide target material and preparation method thereof

Abstract

The invention 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; putting the mixed powder into deionized water, adding a dispersing agent, and blending to obtain slurry; the slurry is subjected to high-energy sanding, and a binder is added before sanding is finished; performing spray granulation on the slurry to obtain spherical granulation powder; carrying out compression molding on the spherical granulation powder, and carrying out cold isostatic pressing to obtain a target material biscuit; and the target biscuit is subjected to degreasing and sintering integrated treatment, and the high-work-function metal oxide target is obtained. The high-work-function metal oxide target material disclosed by the embodiment of the invention is small in grain size, uniform in distribution, high in target material density and excellent in electrical property, and can be used for preparing a flexible OLED anode layer thin film material, the device structure is simplified, and the cost is reduced and the efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of sputtering target materials, and in particular relates to a high work function metal oxide target material and a preparation method thereof. Background Art

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

[0003] In OLED devices, the most commonly used anode thin film material is ITO, whose work function (WF) is around -4.7eV. However, the highest occupied molecular orbital (HOMO) energy level of the organic hole transport layer is usually about -5.7eV. Since the work function of ITO does not match the HOMO energy level of the organic layer, this will lead to a decrease in the hole injection efficiency, which in turn affects the turn-on voltage and overall power consumption of the device. In order to solve this problem, a hole injection layer (HIL) is usually added between the anode and the organic hole transport layer. The HOMO energy level of this layer is about -5.2eV, which can better match the energy levels of the anode and the organic layer, thereby improving the hole injection efficiency. However, this method will not only increase the preparation procedures of OLED devices, but also increase costs. Therefore, it is urgent to develop transition metal oxide anode materials with high work function, high light transmittance and 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, comprising:

[0005] Mixing high work function metal oxide powder, indium oxide powder and zinc oxide powder according to 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 grinding and a binder is added before the end of the sand grinding;

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

[0009] The spherical granulated powder is molded and cold isostatically pressed to obtain a target blank;

[0010] The target material blank is subjected to degreasing and sintering integration treatment to obtain a high work function metal oxide target;

[0011] Among them, the integrated debinding and sintering process specifically includes:

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

[0013] The temperature is raised from the debinding temperature to the first step temperature of 900-1100°C, the heating rate is 0.5-3°C / min, and the temperature is kept for 6-12 hours. The sintering atmosphere is oxygen, and the oxygen flow rate is 3-12L / min;

[0014] The temperature is raised from the first step temperature to the second step temperature of 1450-1550°C at a rate of 3-5°C / min without heat preservation;

[0015] Cool down from the second step temperature to the third step sintering temperature of 1150-1400°C, with a cooling rate of 10-20°C / min, and keep warm for 12-36h;

[0016] Cool down from the third step temperature to the fourth step temperature of 600-800℃, the cooling rate is 1-3℃ / min, keep warm for 3-6h, and adjust the sintering atmosphere to air with an air flow rate of 3-12L / min;

[0017] The temperature is cooled from the fourth step temperature to 200°C at a cooling rate of 3-10°C / min, and then naturally cooled to room temperature.

[0018] In the preparation method of high work function metal oxide target disclosed in some embodiments, the purity of 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 to 1000 nm.

[0019] In the preparation method of high work function metal oxide target disclosed in some embodiments, the mass ratio of zinc oxide powder to indium oxide powder is 10-20:80-90; the ratio of the mass of 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 a high work function metal oxide target, wherein the high work function metal oxide powder is MoO3, CoO, WO3, NiO or TiO2.

[0021] In some embodiments of the preparation method of high work function metal oxide target disclosed, 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.

[0022] In the method for preparing a high work function metal oxide target disclosed in some embodiments, the ball-to-material ratio of high-energy sand milling is 1 to 5:1 and the time is 20 to 80 minutes.

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

[0024] In the method for preparing a high work function metal oxide target disclosed in some embodiments, the molding pressure is 30 to 80 MPa, and the cold isostatic pressing pressure is 200 to 350 MPa.

[0025] In the method for preparing a high work function metal oxide target disclosed in some embodiments, the relative density of the target blank is not less than 60%.

[0026] The high work function metal oxide target disclosed in some embodiments is obtained by the above-mentioned preparation method of the high work function metal oxide target; the relative density of the high work function metal oxide target is not less than 99.5%, the resistance is 0.2 to 6 mΩ·cm, and the work function is 5.0 to 6.5 eV.

[0027] The method for preparing a high work function metal oxide target disclosed in an embodiment of the present invention selects IZO with high transmittance and high conductivity as the main body, adds high work function metal oxide, and adopts a spray granulation process to obtain a mixed powder with uniform size distribution; an integrated degreasing and sintering treatment method is selected, and combined with a multi-step variable temperature sintering process, the target blank is sintered under a set oxygen flow rate, which can inhibit abnormal grain growth, is conducive to obtaining refined grains, reduces the generation of oxygen vacancies, and improves the density of the target material, and finally obtains a high work function metal oxide target with uniform and refined structure; the high work function metal oxide target disclosed in an embodiment of the present invention has a small grain size, uniform distribution, high target density, and excellent electrical properties, and can be used to prepare a flexible OLED anode layer thin film material, simplify the device structure, and reduce costs and increase efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 2 Phase structure diagram of Mo-IZO target material in Example 1. DETAILED DESCRIPTION

[0030] The word "embodiment" used here as an "exemplary" does not necessarily mean that any embodiment described is superior to or better than other embodiments. Unless otherwise specified, the performance index tests in the embodiments of this application are performed using conventional test methods in the art. It should be understood that the terms described in this application are only used to describe specific implementation methods and are not used to limit the content disclosed in this application.

[0031] Unless otherwise specified, the technical and scientific terms used in this document have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0032] The terms "substantially" and "approximately" used herein are used to describe small fluctuations. For example, they can refer to 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%. The numerical data represented or presented in the range format herein are used only for convenience and brevity, and should therefore be flexibly interpreted as including not only the values ​​clearly listed as the limits of the range, but also all independent values ​​or sub-ranges contained in the range. For example, the numerical range of "1-5%" should be interpreted as including not only the clearly listed values ​​of 1% to 5%, but also the independent values ​​and sub-ranges within the range shown. Therefore, independent values ​​such as 2%, 3.5% and 4% and sub-ranges such as 1%-3%, 2%-4% and 3%-5% are included in this numerical range. This principle also applies to the range of only one numerical value. In addition, such an interpretation applies regardless of the width of the range or the characteristics described.

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

[0034] In order to better illustrate the content of the present application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present application.

[0035] Under the premise of no conflict, the technical features disclosed in the embodiments of the present application can be arbitrarily combined, and the obtained technical solutions belong to the contents disclosed in the embodiments of the present application. It should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like mentioned in the present application indicate the orientation or position relationship based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the technical features and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention, unless it conflicts with the context. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance, unless it conflicts with the context.

[0036] In some embodiments, a method for preparing a high work function metal oxide target comprises:

[0037] The high work function metal oxide powder, indium oxide powder and zinc oxide powder are mixed into a mixed powder according to a set mass ratio; 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 100-1000nm; the mass ratio of zinc oxide powder to indium oxide powder is 10-20:80-90; the ratio of the mass 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; the mass ratio of indium oxide to zinc oxide is controlled to ensure the density and conductivity of the high work function metal oxide target;

[0038] The mixed powder is placed in deionized water, and a dispersant is added to prepare a slurry; generally, 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, 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 an appropriate range, which is conducive to ball milling to obtain a mixed powder slurry with a narrow particle size distribution; the dispersant is conducive to the dispersion of the mixed powder in the 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 can increase the viscosity of the slurry, connect the particles in the slurry, improve the granulation performance of the slurry, and ensure that the slurry has a high sphericity after spray granulation, which is beneficial to the next step of green blank forming; generally, the binder is added about ten minutes before the end of the sand milling, and the binder is a colloidal aqueous solution of polyvinyl alcohol with a concentration of 8-15%; generally, the dispersant and the binder can be completely removed in the subsequent degreasing and sintering process, and will not affect the sintering performance of the high work function metal oxide target;

[0040] The slurry is sprayed and granulated to obtain spherical granulated powder; the spherical granulated powder has high dryness, high sphericity and uniform particle size distribution, and can improve the sintering activity and reduce the sintering temperature in the subsequent degreasing and sintering process;

[0041] The spherical granulated powder is molded and 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 material blank is subjected to degreasing and sintering integration treatment to obtain a high work function metal oxide target;

[0043] Among them, the integrated debinding and sintering process specifically includes:

[0044] The target blank is placed in a degreasing and sintering integrated furnace, heated to a degreasing temperature of 450-650°C, with a heating rate of 0.5-1°C / min, and kept warm for 6-12 hours. The degreasing atmosphere is air, and the air flow rate is 3-12L / min. The air atmosphere can absorb and discharge lipid gases, and the air flow during the degreasing stage can better remove the high molecular substances in the dispersant and binder. Keeping warm at a certain temperature can volatilize lipids from the blank to prevent it from affecting the further densification of the target material.

[0045] The temperature is raised from the debinding temperature to the first step temperature of 900-1100°C, the heating rate is 0.5-3°C / min, and the temperature is kept for 6-12h. The sintering atmosphere is oxygen, and the oxygen flow rate is 3-12L / min. Usually, the holding time at the first step temperature cannot be greater than 25h to prevent the grain size from growing due to too long holding time. The first step holding temperature is set in the phase change temperature range of the target blank, so that the phase change reacts completely and the target blank begins to shrink initially.

[0046] The temperature is raised from the first step temperature to the second step temperature of 1450-1550°C, with a heating rate of 3-5°C / min, without heat preservation; the second temperature step is the highest temperature point, without heat preservation, and is generally set according to the material system, 50-200°C higher than the third step temperature, in order to reach the driving temperature of grain growth in the target blank, stimulate the growth of grains, and accelerate the densification rate;

[0047] Cool down from the second step temperature to the third step sintering temperature of 1150-1400℃, the cooling rate is 10-20℃ / min, and the temperature is kept for 12-36h; the third temperature step is a long-term holding temperature, which is set to the temperature with the maximum shrinkage rate of the target blank. In this stage, the grain growth pores are closed and the densification process is greatly accelerated;

[0048] The temperature is lowered from the third step temperature to the fourth step temperature of 600-800°C, the cooling rate is 1-3°C / min, and the temperature is kept for 3-6 hours. The sintering atmosphere is adjusted to air, and the air flow rate is 3-12L / min. The fourth step temperature is to prevent the sample from cracking at a lower temperature due to too fast cooling. Since the fourth step temperature is greatly reduced, and the oxygen atmosphere mainly works at high temperature and is used to prevent the oxide from decomposing at high temperature, the oxygen atmosphere is adjusted to air atmosphere at this time to reduce costs.

[0049] The temperature is cooled from the fourth step temperature to 200°C at a cooling rate of 3-10°C / min, and then naturally cooled to room temperature.

[0050] Usually, the sintering process is carried out in an oxygen atmosphere, because at high temperatures, zinc oxide and indium oxide volatilize to varying degrees, which is not conducive to the stability of the target material composition and the density of the target material; the sintering heating rate cannot be too fast or too slow. A heating rate that is too fast will cause uneven heating of the target blank, incomplete reaction, and cause cracking of the target material. A heating rate that is too slow will result in a too long sintering time, which is not conducive to production.

[0051] Generally, the sintering temperature cannot be higher than 1600°C. Indium oxide decomposes too quickly at a high temperature higher than 1600°C, which is not conducive to obtaining a target material 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-material ratio of high-energy sand milling is 1 to 5:1, and the time is 20 to 80 minutes. Generally, the slurry is placed in a high-energy sand mill, and high-energy sand milling is performed using zirconium oxide ball milling beads with a diameter of 1 mm. During the high-energy sand milling process, the mixed powder particles in the slurry are crushed, and the powder particle size is reduced to form nanoparticles with a small particle size distribution range and uniform distribution, which is conducive to the subsequent granulation process; the metal oxide powder in the slurry is efficiently sand milled in the high-energy sand mill to form a refined particle size, which effectively increases the sintering activity of the powder.

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

[0055] In some embodiments, the sand-milled slurry is aged 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 rotation 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, the air inlet temperature of the granulator is 200-300°C, the exhaust temperature is 80-100°C, the frequency is 30-50 Hz, and the particle size of the obtained granulated powder is about 200-300 nm.

[0058] In some embodiments, the high work function metal oxide target is obtained by the above-mentioned 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 resistance 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 in conjunction with embodiments.

[0060] Example 1

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

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

[0063] 427.5g ZnO powder, 712.5g In2O3 powder and 60g MoO3 powder were mixed into 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 720 g of deionized water, and 12 g of dispersant was added to prepare a slurry; wherein the solid content of the slurry was 62.5% and the viscosity was 40 mPa·s;

[0065] The slurry was subjected to high-energy sand milling for 60 minutes, and 12g of a binder was added 10 minutes before the end of the sand milling to fully mix MoO3, In2O3 and ZnO and refine the particles; the slurry was then placed in a granulator for spray granulation, the inlet air temperature of the granulator was 200°C, the exhaust air temperature was 80°C, and the frequency was 30Hz, to obtain 984g of spherical Mo-IZO granulated powder, with a powder recovery rate of about 82%; Figure 1 As shown, the Mo-IZO granulated powder has good spheroidization, uniform particle size distribution, and no agglomeration of the powder;

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

[0067] The target blank is subjected to an integrated degreasing and sintering process, which specifically includes:

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

[0069] The temperature was raised from the debinding temperature to the first step temperature of 1000°C at a heating rate of 3°C / min and kept at this temperature for 10 hours. The sintering atmosphere was oxygen and the oxygen flow rate was 6L / min.

[0070] The temperature was raised from the first step temperature to the second step temperature of 1450°C at a rate of 3°C / min without heat preservation;

[0071] Cool down from the second step temperature to the third step sintering temperature of 1350℃, the cooling rate is 20℃ / min, and keep warm for 20h;

[0072] Cool down from the third step temperature to the fourth step temperature of 800℃, the cooling rate is 3℃ / min, keep warm for 3h, and adjust the sintering atmosphere to air with an air flow rate of 6L / min;

[0073] Cool down from the fourth step temperature to 200°C at a cooling rate of 5°C / min, and then cool naturally to room temperature;

[0074] The Mo-IZO target material was obtained, and its relative density was 99.8%, its resistivity was 0.80 mΩ·cm, and its work function was 5.8 eV; Figure 2 As shown, the Mo-IZO target has small grain size and uniform distribution, 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, wherein 450g of ZnO powder, 690g of In2O3 powder, and 96g of MoO3 powder are weighed, and the mass ratio of MoO3 to In2O3-ZnO is 8:92; 960g of spherical Mo-IZO granulated powder is obtained, and the powder recovery rate is about 80%; the relative density of the obtained target blank is 63%; the relative density of the obtained Mo-IZO target is 99.6%, the resistivity is 0.42mΩ·cm, and the work function is 6.0eV.

[0077] Example 3

[0078] Example 3 discloses a method for preparing a high work function metal oxide target, referring to Example 1, wherein MoO3 powder is replaced by WO3 powder, 427.5 g of ZnO powder, 712.5 g of In2O3 powder, and 90 g of WO3 powder are weighed, and the mass ratio of WO3 to In2O3-ZnO is 5:95; the obtained spherical W-IZO granulated powder has a powder recovery rate of about 85%; the relative density of the obtained target blank is 61%; the obtained W-IZO target has a relative density of 99.6%, a resistivity of 5.0 mΩ·cm, and a work function of 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, wherein 450 g of ZnO powder, 690 g of In2O3 powder, and 96 g of WO3 powder are weighed, and the mass ratio of WO3 to In2O3-ZnO is 8:92; the obtained spherical W-IZO granulated powder has a powder recovery rate of about 86%; the relative density of the obtained target blank is 63%; the obtained W-IZO target has a relative density of 99.6%, a resistivity of 3.0 mΩ·cm, and a work function of 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, wherein MoO3 powder is replaced by TiO2 powder, 427.5 g of ZnO powder, 712.5 g of In2O3 powder, 90 g of TiO2 powder, and the mass ratio of TiO2 to In2O3-ZnO is 5:95; the obtained spherical Ti-IZO granulated powder has a powder recovery rate of about 86%; the relative density of the obtained target blank is 61%; the obtained Ti-IZO target has a relative density of 99.5%, a resistivity of 5.2 mΩ·cm, and a work function of 5.5 eV.

[0083] Example 6

[0084] Example 6 discloses a method for preparing a high work function metal oxide target, referring to Example 5, wherein 450 g of ZnO powder, 690 g of In2O3 powder, and 96 g of TiO2 powder are weighed, and the mass ratio of TiO2 to In2O3-ZnO is 8:92; the obtained spherical Ti-IZO granulated powder has a powder recovery rate of about 85%; the relative density of the obtained target blank is 62%; the obtained Ti-IZO target has a relative density of 99.8%, a resistivity of 3.2 mΩ·cm, and a work function of 5.7 eV.

[0085] The method for preparing a high work function metal oxide target disclosed in an embodiment of the present invention selects IZO with high transmittance and high conductivity as the main body, adds high work function metal oxide, and adopts a spray granulation process to obtain a mixed powder with uniform size distribution; an integrated degreasing and sintering treatment method is selected, and combined with a multi-step variable temperature sintering process, the target blank is sintered under a set oxygen flow rate, which can inhibit abnormal grain growth, is conducive to obtaining refined grains, reduces the generation of oxygen vacancies, and improves the density of the target material, and finally obtains a high work function metal oxide target with uniform and refined structure; the high work function metal oxide target disclosed in an embodiment of the present invention has a small grain size, uniform distribution, high target density, and excellent electrical properties, and can be used to prepare a flexible OLED anode layer thin film material, simplify the device structure, and reduce costs and increase efficiency.

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

Claims

1. A method for preparing a high work function metal oxide target, characterized in that: include: Mixing high work function metal oxide powder, indium oxide powder and zinc oxide powder according to a set mass ratio to form a mixed powder; The mixed powder is placed in deionized water and a dispersant is added to prepare a slurry; The slurry is subjected to high-energy sand grinding and a binder is added before the end of the sand grinding; The slurry is spray-granulated to obtain spherical granulated powder; The spherical granulated powder is molded and cold isostatically pressed to obtain a target blank; The target material blank is subjected to degreasing and sintering integration treatment to obtain a high work function metal oxide target; The degreasing and sintering integrated process specifically includes: The target blank is placed in a degreasing and sintering integrated furnace, heated to a degreasing temperature of 450-650°C, a heating rate of 0.5-1°C / min, and kept warm for 6-12 hours. The degreasing atmosphere is air, and the air flow rate is 3-12L / min. The temperature is raised from the debinding temperature to the first step temperature of 900-1100°C, the heating rate is 0.5-3°C / min, and the temperature is kept for 6-12 hours. The sintering atmosphere is oxygen, and the oxygen flow rate is 3-12L / min; The temperature is raised from the first step temperature to the second step temperature of 1450-1550°C at a rate of 3-5°C / min without heat preservation; Cool down from the second step temperature to the third step sintering temperature of 1150-1400°C, with a cooling rate of 10-20°C / min, and keep warm for 12-36h; Cool down from the third step temperature to the fourth step temperature of 600-800℃, the cooling rate is 1-3℃ / min, keep warm for 3-6h, and adjust the sintering atmosphere to air with an air flow rate of 3-12L / min; The temperature is cooled from the fourth step temperature to 200°C at a cooling rate of 3-10°C / min, and then naturally cooled to room temperature.

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

3. The method for preparing a high work function metal oxide target according to claim 1, characterized in that: The mass ratio of the zinc oxide powder to the indium oxide powder is 10-20:80-90; the mass ratio of the high work function metal oxide powder to the total mass of the zinc oxide powder and the indium oxide powder is 2-10:90-98.

4. 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 is MoO3, CoO, WO3, NiO or TiO2.

5. The method for preparing a high work function metal oxide target according to claim 1, characterized in that: 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, 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.

6. 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 1-5:1, and the time is 20-80 minutes.

7. 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, the air inlet temperature of the granulator is 200-300° C., the exhaust temperature is 80-100° C., and the frequency is 30-50 Hz.

8. The method for preparing a high work function metal oxide target according to claim 1, characterized in that: The molding pressure is 30-80 MPa, and the cold isostatic pressing pressure is 200-350 MPa.

9. The method for preparing a high work function metal oxide target according to claim 1, characterized in that: The relative density of the target blank is not less than 60%.

10. 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 9; the high work function metal oxide target has a relative density of not less than 99.5%, a resistance of 0.2 to 6 mΩ·cm, and a work function of 5.0 to 6.5 eV.

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