Co-doped tin oxide material and preparation method and application thereof

Abstract

The invention belongs to the technical field of transparent conductive oxide target materials, and particularly relates to a co-doped tin oxide material and a preparation method and application thereof. The co-doped tin oxide material provided by the invention comprises the following elements: tin, doped metal elements and oxygen, the doped metal elements are selected from two or more of transition metal elements, rare earth metal elements, antimony, rhenium and aluminum. The co-doped tin oxide material has high density and low resistivity, and the transparent conductive film prepared from the co-doped tin oxide material is high in uniformity, excellent in conductivity and optical performance, low in sheet resistance, wide in band gap and high in transmittance.

Description

Technical Field

[0001] The present invention belongs to the technical field of transparent conductive oxide targets, and particularly relates to a co-doped tin oxide material, a preparation method thereof, and an application thereof. Background Art

[0002] As a wide-bandgap semiconductor material, SnO2 has attracted much attention due to its good chemical stability, mechanical strength, and thermal stability, and is regarded as a powerful alternative to ITO (indium tin oxide). However, the inherently low conductivity of SnO2 limits its commercial application.

[0003] In the prior art, the conductivity of SnO2 thin films can be significantly improved by doping elements such as Sb, F, Ta, and Nb. Sb is a commonly used dopant. Although Sb acts as a donor, the transition of its +1 charge state to the neutral charge state occurs at about 0.15 eV above the conduction band minimum (CBM). The prior art uses an antimony-doped tin oxide sintered target, and the conductivity and transmittance of the film deposited by physical vapor deposition (PVD) of this target are not good. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a co-doped tin oxide material, a preparation method thereof, and an application thereof. The co-doped tin oxide material has high density and low resistivity. The transparent conductive film prepared therefrom not only has high uniformity, but also simultaneously has excellent conductive performance and optical performance, and has low sheet resistance, wide bandgap, and high transmittance.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a co-doped tin oxide material, and the element composition includes: tin, a doped metal element, and oxygen;

[0007] The doped metal element is selected from two or more of transition metal elements, rare earth metal elements, antimony, rhenium, and aluminum.

[0008] Preferably, the rare earth metal element includes one or several of hafnium, lanthanum, cerium, and neodymium;

[0009] The transition metal element includes one or several of tantalum, tungsten, titanium, molybdenum, niobium, vanadium, chromium, iron, cobalt, nickel, manganese, copper, and zinc.

[0010] Preferably, the total molar percentage content of the doped metal element in the metal elements of the co-doped tin oxide material < 15 mol%.

[0011] Preferably, the relative density of the co-doped tin oxide material ≥ 99%, and the bulk resistivity ≤ 6 mΩ·cm.

[0012] The present invention also provides a method for preparing the co-doped tin oxide material described in the above technical solution, comprising the following steps:

[0013] Mix SnO2 powder, oxide powder of doped metal element, dispersant, defoamer and solvent, and perform sand grinding. Then, mix the obtained slurry with a curing agent for granulation to obtain doped tin oxide powder;

[0014] Anneal and form the doped tin oxide powder in sequence to obtain a doped tin oxide green body;

[0015] Perform low-temperature sintering, medium-temperature sintering and high-temperature sintering on the doped tin oxide green body in sequence to obtain the co-doped tin oxide material.

[0016] Preferably, the annealing treatment is carried out in an air environment; the temperature of the annealing treatment is 1200 - 1600 °C, and the holding time is 1 - 5 h.

[0017] Preferably, the temperature of the low-temperature sintering is 450 - 650 °C, and the holding time is 2 - 12 h;

[0018] The temperature of the medium-temperature sintering is 1000 - 1200 °C, and the holding time is 8 - 48 h;

[0019] The temperature of the high-temperature sintering is 1480 - 1520 °C, and the holding time is 20 - 48 h;

[0020] The low-temperature sintering, medium-temperature sintering and high-temperature sintering are all carried out in an oxygen-containing environment throughout the process; the purity of oxygen in the oxygen-containing environment is ≥98%.

[0021] The present invention also provides an application of the co-doped tin oxide material described in the above technical solution or the co-doped tin oxide material prepared by the preparation method described in the above technical solution in a physical vapor deposition target.

[0022] The present invention also provides a transparent conductive film, which is formed by physical vapor deposition coating of a physical vapor deposition target on a substrate;

[0023] The physical vapor deposition target is the co-doped tin oxide material described in the above technical solution or the co-doped tin oxide material prepared by the preparation method described in the above technical solution.

[0024] Preferably, the thickness of the transparent conductive film is 50 - 150 nm, the sheet resistance is 1.9 - 3.5 mΩ·cm, the average transmittance is 84 - 85%, and the band gap is 3.8 - 4 eV.

[0025] The present invention provides a co-doped tin oxide material, the elemental composition of which includes: tin, doped metal elements and oxygen; the doped metal elements are selected from two or more of transition metal elements, rare earth metal elements, antimony, rhenium and aluminum. By introducing two or more doped metal elements, the present invention synergistically acts on the crystal structure and electronic structure of SnO2. Co-doping not only enhances the compactness of SnO2, reduces the defects and pores of the co-doped tin oxide material, and solves the problems of abnormal discharge and nodulation in the PVD coating process, thereby improving the uniformity and compactness of the thin film prepared therefrom. At the same time, the doped metal elements play an effective donor energy level role in the lattice structure of tin oxide. They can increase the concentration of carriers (such as electrons or holes), and promote the migration of these carriers inside the material, reducing the bulk resistivity, thereby greatly enhancing the electrical conductivity of the thin film and reducing the sheet resistance of the thin film. Further, by doping different types of impurities (donor impurities or acceptor impurities), the position of the Fermi level in the semiconductor can be changed. Donor impurities are doped with high valence states (such as Ta 5+ , W 6+ , Mo 6+ ) will make the Fermi level close to the bottom of the conduction band, while acceptor impurities are doped with low valence states (such as Zn 2+ , Cu 2+ , Al 3+ ) will make the Fermi level close to the top of the valence band, thereby broadening the band gap of the thin film, adjusting the positions of the bottom of the conduction band and the top of the valence band, improving the transmittance of the thin film, balancing the relationship between electrical conductivity and optical properties, and ensuring that while enhancing the electrical conductivity, the transparency and optical properties of the thin film are not sacrificed. Therefore, tin oxide can be doped and modified by combining a variety of different doped metal elements to obtain tin oxide transparent conductive thin films with a variety of different energy level structures. The results of the examples show that the thin films prepared from the co-doped tin oxide material provided by the present invention have the characteristics that the band gap is greater than 3.3 eV, and the bottom of the conduction band and the top of the valence band both show a downward movement trend. Description of the Drawings

[0026] Figure 1 SEM morphology diagram of the polished surface of the target prepared in Example 1;

[0027] Figure 2 Ultraviolet absorption spectra of the targets prepared in Examples 1-3. Detailed Embodiments

[0028] The present invention provides a co-doped tin oxide material, the elemental composition of which includes: tin, doped metal elements and oxygen;

[0029] The doped metal elements are selected from two or more of transition metal elements, rare earth metal elements, antimony (Sb), rhenium (Re) and aluminum (Al).

[0030] Unless otherwise specified, the present invention has no special requirements for the sources of the raw materials used, and commercially available products well-known to those skilled in the art can be used.

[0031] As an embodiment, the rare earth metal elements include one or more of hafnium (Hf), lanthanum (La), cerium (Ce), and neodymium (Nd); the transition metal elements include one or more of tantalum (Ta), tungsten (W), titanium (Ti), molybdenum (Mo), niobium (Nb), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), copper (Cu), and zinc (Zn).

[0032] In a specific embodiment, the doped metal elements are Ta and Nb, or Zn and Ta, or Sb and Nb.

[0033] As an embodiment, the total molar percentage content of the doped metal elements in the metal elements of the co-doped tin oxide material < 15 mol%, specifically 5 - 14 mol% in specific embodiments, and the molar percentage content of tin is ≥ 85 mol%, specifically 86 - 95 mol% in specific embodiments. The present invention has no special limitation on the ratio between different types of doped metal elements, and any ratio can be used.

[0034] As an embodiment, the relative density of the co-doped tin oxide material ≥ 99%, specifically 99.19%, 99.47%, or 99.63% in specific embodiments, and the volume resistivity ≤ 6 mΩ·cm, specifically 2.54 mΩ·cm, 4.37 mΩ·cm, or 5.61 mΩ·cm in specific embodiments.

[0035] In the present invention, the doped metal elements are classified into two categories according to their functions. The function of the first category is to increase the carrier concentration and conductivity of tin oxide, including antimony, tantalum, molybdenum, tungsten, niobium, rhenium, hafnium, and rare earth metal elements such as lanthanum, cerium, and neodymium. The valence states of these metal cations are higher than that of Sn 4+ or their electron cloud densities are higher. The function of the second category is to improve the sintering properties of the tin oxide target, including elements such as titanium, vanadium, chromium, iron, cobalt, aluminum, nickel, manganese, copper, and zinc. The oxides of these elements have lower melting points and are prone to form liquid-phase sintering during the sintering process, thereby increasing the sintering density. The combination of the above two categories of elements as doping elements in a binary or higher binary form is expected to improve the optical, electrical, or mechanical properties of the transparent conductive film, and can play a role in adjusting the energy level structure of SnO2 under careful control of the doping amount. For example, when tantalum niobium, tantalum zinc, and antimony niobium are used as co-doping elements, they can increase the band gap of SnO2 and lower the positions of the conduction band bottom and valence band top of SnO2.

[0036] In the co-doped tin oxide material provided by the present invention, the co-doped elements finally exist in the form of oxides and may also form a third phase with tin oxide, such as Ta2SnO6; the transition metal elements and rare earth metal elements do not necessarily need to be doped simultaneously. The doping effect of the transition metal elements is mainly high-valence doping and sintering aid, while the effect of the rare earth metal elements is more complex than that of the transition metal elements. In addition to sintering aid and high-valence doping, there is also the effect of adjusting the electron orbit.

[0037] By adjusting the doping ratios and preparation conditions of the first doping metal element and the second doping metal element in the present invention, the purpose of precisely controlling the distribution and state of the doping elements in the SnO2 transparent conductive film can be achieved, so as to balance the relationship between conductivity and light transmittance, and ensure that while improving the conductive performance, the transparency and optical properties of the film are not sacrificed.

[0038] The present invention also provides a preparation method of the co-doped tin oxide material described in the above technical solution, including the following steps:

[0039] After mixing SnO2 powder, oxide powder of doped metal elements, dispersant, defoamer and solvent and performing sand grinding, the obtained slurry is mixed with a curing agent for granulation to obtain doped tin oxide powder;

[0040] The doped tin oxide powder is annealed and formed in sequence to obtain a doped tin oxide green body;

[0041] The doped tin oxide green body is subjected to low-temperature sintering, medium-temperature sintering and high-temperature sintering in sequence to obtain the co-doped tin oxide material.

[0042] In the present invention, SnO2 powder, oxide powder of doped metal elements, dispersant, defoamer and solvent are mixed and subjected to sand grinding, and then the obtained slurry is mixed with a curing agent for granulation to obtain doped tin oxide powder.

[0043] As an implementation manner, the particle size D50 of the SnO2 powder is 0.1 - 1 μm, and is 0.4 μm in a specific embodiment; the purity of the SnO2 powder is ≥99.99%, and is 99.99% in a specific embodiment.

[0044] As an implementation manner, the particle size D50 of the oxide powder of the doped metal elements is 0.1 - 1 μm, and is 0.5 μm in a specific embodiment; the purity of the oxide powder of the doped metal elements is ≥99.99%, and is 99.99% in a specific embodiment.

[0045] As an embodiment, the dispersant includes an alcohol solvent and / or an anionic surfactant; the alcohol solvent includes one or more of ethanol, ethylene glycol, methyl pentanol, and isopropyl alcohol, specifically ethanol, ethylene glycol, or isopropyl alcohol in specific embodiments; the anionic surfactant is sodium dodecyl sulfate; the mass ratio of the dispersant to the total mass of the SnO2 powder and the oxide powder of the doped metal element is 10 - 50:4000 - 5000, specifically 20 - 30:4000 - 5000 in specific embodiments.

[0046] As an embodiment, the defoamer includes alkanes and / or fatty acids; the alkanes include ethylene oxide and / or propylene oxide copolymers, specifically ethylene oxide and propylene oxide copolymer in specific embodiments; the fatty acids include lauric acid and / or palmitic acid, specifically lauric acid in specific embodiments; the mass ratio of the defoamer to the total mass of the SnO2 powder and the oxide powder of the doped metal element is 1 - 10:4000 - 5000, specifically 5:4000 - 5000 in specific embodiments.

[0047] As an embodiment, the solvent is water; the mass ratio of the solvent to the total mass of the SnO2 powder and the oxide powder of the doped metal element is 0.5 - 2:1, specifically 1 - 1.5:1 in specific embodiments.

[0048] As an embodiment, the rotation speed of the sand mill is 1500 - 2500 rpm, specifically 2000 rpm in specific embodiments; the time of sand milling is 0.5 - 5 h, specifically 0.5 - 3 h in specific embodiments.

[0049] As an embodiment, the granulation is spray granulation; during the spray granulation process, the rotation speed of the spray disk is 15000 - 20000 rpm, specifically 16600 rpm in specific embodiments, the inlet air temperature is 160 - 230 °C, specifically 205 °C in specific embodiments; the particle size of the doped tin oxide powder is 0.1 - 2 μm, specifically 0.2 μm in specific embodiments. The present invention converts the slurry obtained by sand milling into small and uniform particles through spray granulation, improving the fluidity and formability of the material.

[0050] As an embodiment, when the doped metal element includes the first doped metal element, the second doped metal element... the nth doped metal element, in the present invention, the SnO2 powder, the oxide powder of the first doped metal element, the first dispersant, the first defoamer, and the first solvent are mixed and subjected to the first sand milling, and then the first granulation is carried out to obtain the first doped tin oxide powder;

[0051] The first doped tin oxide powder, the oxide powder of the second doped metal element, the second dispersant, the second defoamer, and the second solvent are mixed and subjected to the second sand milling, and then the second granulation is carried out to obtain the second doped tin oxide powder;

[0052] Mix the n-1 doped tin oxide powder, the oxide powder of the nth doping metal element, the nth dispersant, the nth defoamer, and the nth solvent for the nth sanding, and mix the resulting slurry with a curing agent for the nth granulation to obtain doped tin oxide powder.

[0053] For example: when the doping metal element includes two kinds, namely the first doping metal element and the second doping metal element, the processes of sanding and granulation are as follows:

[0054] Mix SnO2 powder, the oxide powder of the first doping metal element, the first dispersant, the first defoamer, and the first solvent for the first sanding, and then perform the first granulation to obtain the first doped tin oxide powder;

[0055] Mix the first doped tin oxide powder, the oxide powder of the second doping metal element, the second dispersant, the second defoamer, and the second solvent for the second sanding, and mix the resulting slurry with a curing agent and then perform the second granulation to obtain doped tin oxide powder.

[0056] In the present invention, the first dispersant, the first defoamer, the first solvent, the second dispersant, the second defoamer, and the second solvent are the same as the above-mentioned dispersants, defoamers, and solvents, and will not be elaborated here. The processes of the first granulation and the second granulation are the same as the above-mentioned granulation, and will not be elaborated here.

[0057] As an implementation manner, for the first sanding, first mix a part of SnO2 powder, the oxide powder of the first doping metal element, the first dispersant, the first defoamer, and the first solvent for the first-stage sanding, and then add the remaining SnO2 powder for the second-stage sanding; the rotation speeds of the first-stage sanding and the second-stage sanding are independently 1500 - 2500 rpm, and are 2000 rpm in specific embodiments; the time of the first-stage sanding is 0.5 - 1 h, and is 0.5 h in specific embodiments; the time of the second-stage sanding is 2 - 5 h, and is 2.5 h in specific embodiments; the mass ratio of the oxide powder of the first doping metal element to the part of SnO2 powder is 1:1 - 5, and is 1:2 - 4 in specific embodiments.

[0058] As an implementation manner, the mass ratio of the SnO2 powder to the oxide powder of the first doped metal element is 4500-4900:500-100, specifically 4750:150 or 4900:100 in specific embodiments; the mass ratio of the first dispersant to the total mass of the SnO2 powder and the oxide powder of the first doped metal element is 10-200:5000, specifically 20-100:5000 in specific embodiments; the mass ratio of the first defoamer to the total mass of the SnO2 powder and the oxide powder of the first doped metal element is 1-20:5000, specifically 5-10:5000 in specific embodiments; the first solvent is water; the mass ratio of the first solvent to the total mass of the SnO2 powder and the oxide powder of the first doped metal element is 1-1.5:1, specifically 1-1.2:1 in specific embodiments.

[0059] The sanding of the present invention in stages can make the SnO2 powder and the oxide powder of the first doped metal element be mixed evenly, ensuring the uniformity and fineness of the material mixture.

[0060] As an implementation manner, the mass ratio of the first doped tin oxide powder to the oxide powder of the second doped metal element is 3500-3970:500-30, specifically 3970:30 or 3900:100 in specific embodiments; the mass ratio of the second dispersant to the total mass of the first doped tin oxide powder and the oxide powder of the second doped metal element is 10-200:4000, specifically 20-100:4000 in specific embodiments; the mass ratio of the second defoamer to the total mass of the first doped tin oxide powder and the oxide powder of the second doped metal element is 1-20:4000, specifically 5-10:4000 in specific embodiments.

[0061] As an implementation manner, the second solvent is water; the mass ratio of the second solvent to the total mass of the first doped tin oxide powder and the oxide powder of the second doped metal element is 1-1.5:1, specifically 1-1.2:1 in specific embodiments.

[0062] As an implementation manner, for the second sanding, first mix part of the first doped tin oxide powder, the oxide powder of the second doped metal element, the second dispersant, the second defoamer and the second solvent for the third-stage sanding, and then add the remaining first doped tin oxide powder for the fourth-stage sanding; the rotation speeds of the third-stage sanding and the fourth-stage sanding are independently 1500-2500 rpm, specifically 2000 rpm in specific embodiments; the time of the third-stage sanding is 0.5-1 h, specifically 0.5 h in specific embodiments; the time of the fourth-stage sanding is 2-5 h, specifically 2.5 h in specific embodiments; the mass ratio of the oxide powder of the second doped metal element to part of the first doped tin oxide powder is 1:1-5, specifically 1:5 in specific embodiments.

[0063] As an implementation manner, the curing agent includes one or several of polyvinyl alcohol, vinyl acetate, ethyl cellulose, acetal resin, and acrylic polymer, specifically polyvinyl alcohol in a specific embodiment; the acrylic polymer is acrylic resin; the total mass ratio of the curing agent to the SnO2 powder and the oxide powder doped with metal elements is 100-300:4000-5000, specifically 150-250:4000 in a specific embodiment.

[0064] As an implementation manner, the obtained slurry and the curing agent are mixed under stirring; the stirring time is 15-30 min, specifically 20-25 min in a specific embodiment. The present invention does not have special limitations on the stirring rate, and it is sufficient to stir evenly. The present invention ensures that the curing agent is evenly dispersed in the slurry through stirring.

[0065] As an implementation manner, the tapped density of the doped tin oxide powder is 1.5-2.5 g / cm 3 , specifically 1.96 g / cm 3 .

[0066] After obtaining the doped tin oxide powder, the present invention anneals and shapes the doped tin oxide powder in sequence to obtain a doped tin oxide green body.

[0067] As an implementation manner, the annealing treatment is carried out in an air environment; the temperature of the annealing treatment is 1200-1600 °C, specifically 1300-1600 °C in a specific embodiment, and the heat preservation time is 1-5 h, specifically 2-4 h in a specific embodiment.

[0068] As an implementation manner, the tapped density of the doped tin oxide powder after the annealing treatment is 3-4.5 g / cm 3 , specifically 3.73 g / cm 3 , 3.76 g / cm 3 or 3.86 g / cm 3 .

[0069] The present invention promotes the combination between the doped tin oxide powder particles through the annealing treatment, improves the tapped density, and thus improves the density and performance of the co-doped tin oxide material.

[0070] As an implementation manner, the shaping includes hydraulic treatment and cold isostatic pressing treatment carried out in sequence; the initial pressure of the hydraulic treatment is 5-20 MPa, specifically 6-10 MPa in a specific embodiment, and the pressure holding time is 5-15 min, specifically 7-13 min in a specific embodiment.

[0071] As an implementation manner, the initial pressure of the cold isostatic pressing treatment is 250-300 MPa, and in a specific embodiment, it is 270 MPa. The pressure holding time is 30-60 min, and in a specific embodiment, it is 40-50 min.

[0072] In the present invention, after the doped tin oxide powder after annealing treatment is preliminarily compacted by hydraulic treatment, it is further pressed by cold isostatic pressing to further improve the density and uniformity, and a dense doped tin oxide green body is obtained.

[0073] Based on tin oxide powder, the present invention first spray granulates to improve the fluidity and formability of the powder, then improves the tapped density through annealing treatment, and finally combines hydraulic and cold isostatic pressing treatments for compaction to prepare a doped tin oxide green body with high density and dense structure.

[0074] After obtaining the doped tin oxide green body, the present invention sequentially performs low-temperature sintering, medium-temperature sintering, and high-temperature sintering on the doped tin oxide green body to obtain the co-doped tin oxide material.

[0075] As an implementation manner, the temperature of the low-temperature sintering is 450-650 °C, and in a specific embodiment, it is 500-650 °C. The heat preservation time is 2-12 h, and in a specific embodiment, it is 5-10 h. The heating rate for heating to the temperature of the low-temperature sintering is 0.5-1 °C / min, and in a specific embodiment, it is 0.7-1 °C / min.

[0076] As an implementation manner, the temperature of the medium-temperature sintering is 1000-1200 °C, and in a specific embodiment, it is 1100-1200 °C. The heat preservation time is 8-48 h, and in a specific embodiment, it is 8-24 h. The heating rate for heating from the temperature of the low-temperature sintering to the temperature of the medium-temperature sintering is 0.5-2 °C / min, and in a specific embodiment, it is 1-2 °C / min.

[0077] As an implementation manner, the temperature of the high-temperature sintering is 1480-1520 °C, and in a specific embodiment, it is 1500 °C. The heat preservation time is 20-48 h, and in a specific embodiment, it is 24-36 h. The heating rate for heating from the temperature of the medium-temperature sintering to the temperature of the high-temperature sintering is 0.1-1 °C / min, and in a specific embodiment, it is 0.5-1 °C / min.

[0078] In the present invention, degreasing is carried out through low-temperature sintering to remove residual moisture and organic substances in the sintered product. Medium-temperature sintering can promote the nucleation growth and densification of grains in the sintered product, and promote the preliminary formation of the crystal structure. Then, high-temperature sintering is carried out to ensure the full growth of grains in the material, so as to increase the grain size and enhance the mechanical properties of the material.

[0079] As an implementation manner, the low-temperature sintering, medium-temperature sintering, and high-temperature sintering are all carried out in an oxygen-containing environment throughout the process; the purity of oxygen in the oxygen-containing environment is ≥98%, and in specific embodiments, it is ≥99%. In the present invention, the sintering process is carried out in an oxygen environment throughout to ensure the integrity of the oxidation process and the purity of the sintered product.

[0080] As an implementation manner, after the high-temperature sintering, the present invention further includes: after cooling the high-temperature sintered product to 400 - 500 °C, naturally cooling it to room temperature. In a specific embodiment, the high-temperature sintered product is cooled to 500 °C and then naturally cooled to room temperature; the cooling rate is 1 - 2 °C / min, and in a specific embodiment, it is 1.2 - 1.5 °C / min.

[0081] The present invention also provides the application of the co-doped tin oxide material described in the above technical solution or the co-doped tin oxide material prepared by the preparation method described in the above technical solution in a physical vapor deposition target.

[0082] The present invention also provides a transparent conductive film, which is formed by physical vapor deposition coating of a physical vapor deposition target on a substrate;

[0083] The physical vapor deposition target is the co-doped tin oxide material described in the above technical solution or the co-doped tin oxide material prepared by the preparation method described in the above technical solution.

[0084] As an implementation manner, the physical vapor deposition is magnetron sputtering; the magnetron sputtering is direct current reactive magnetron sputtering (DC-RMS); the conditions of the magnetron sputtering include: the diameter of the target is 70 - 100 mm, and in a specific embodiment, it is 76 mm, the thickness is 1.5 - 3 mm, and in a specific embodiment, it is 2 mm; the distance between the target and the substrate is 90 - 150 mm, and in a specific embodiment, it is 110 mm; during the magnetron sputtering process, the vacuum degree is 0.5×10 -5 Pa - 1.5×10 -5 Pa, and in a specific embodiment, it is 1.0×10 - 5 Pa, the pressure during film formation is 0.1 - 1 Pa, and in a specific embodiment, it is 0.5 Pa. The additive gases used during the magnetron sputtering process include argon and oxygen, where the oxygen partial pressure is O2 / Ar = 0 - 50%, and in a specific embodiment, it is O2 / Ar 5%. The temperature of the substrate is 25 - 200 °C, and in a specific embodiment, it is 110 °C. The power of the magnetron sputtering is 100 - 150 W, and in a specific embodiment, it is 120 W. The substrate is an alkali-free glass.

[0085] As an embodiment, the thickness of the transparent conductive film is 50 - 150 nm, specifically 100 - 120 nm in specific embodiments, the sheet resistance is 1.9 - 3.5 mΩ·cm, specifically 1.92 - 3.45 mΩ·cm in specific embodiments, the average transmittance is 84 - 85%, specifically 84% or 85% in specific embodiments, the band gap is 3.8 - 4 eV, specifically 3.82 - 3.96 eV in specific embodiments.

[0086] During the physical vapor deposition (PVD) coating process, if there are pores in the target, it will lead to abnormal discharge and thus form nodules. The present invention eliminates the pores in the target by increasing the relative density of the target, thus solving the problems of abnormal discharge and nodulation during the PVD coating process. These improvements not only enhance the stability and coating efficiency of the target, but also greatly improve the controllability of the coating process and the quality of the finished product. Particularly crucial is that the present invention has ingeniously co-doped multiple elements in the SnO2 target. These doping elements can play an important role during the coating process, enabling the prepared transparent conductive film to exhibit good high carrier concentration and mobility characteristics, and achieving a better energy level matching degree. This breakthrough performance improvement opens up new possibilities for the application of transparent conductive films in fields such as optoelectronic display, solar cells, and touchscreens. Especially in the context of pursuing high-performance and indium-free material replacement solutions, it has extremely high application value.

[0087] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention, but they cannot be understood as limitations on the protection scope of the present invention.

[0088] Example 1

[0089] (1) First, select SnO2 powder with a purity of 99.99%, its particle size D50 = 0.4 μm, and at the same time select Ta2O5 powder with the same purity of 99.99%, particle size D50 = 0.5 μm. Subsequently, accurately weigh 750 g of SnO2 powder, 150 g of Ta2O5 powder, and place them in a sand mill together with 5000 g of water for mixing. During the mixing process, add 20 g of dispersant (sodium dodecyl sulfate, methyl amyl alcohol) to improve the powder dispersion, and add 5 g of defoamer (ethylene oxide, propylene oxide copolymer) to prevent bubble generation. The mixing process is carried out at a speed of 2000 rpm for 0.5 h. Subsequently, add 4000 g of SnO2 powder and continue to carry out sand milling at a speed of 2000 rpm for 2.5 h until a uniform and delicate slurry is formed;

[0090] (2) Feed the slurry prepared in step (1) into a spray granulation device, adjust the rotation speed of the spray disk to 16600 rpm, and set the inlet air temperature to 205 °C for granulation to obtain a mixed powder of SnO2 and Ta2O5.

[0091] (3) Select Nb2O5 powder with a purity of 99.99% and a particle size of D50 = 0.4 μm, weigh 100 g, and mix it with 500 g of the mixed powder of SnO2 and Ta2O5 in step (2) and 5000 g of water by sand milling, and add 20 g of dispersant (sodium dodecyl sulfate, methyl amyl alcohol) to improve the dispersibility of the powder, and add 5 g of defoaming agent (ethylene oxide, propylene oxide copolymer) to prevent bubble formation. The mixing process is carried out at a speed of 2000 rpm for 0.5 h, and then 3400 g of the mixed powder of SnO2 and Ta2O5 is added, and the sand milling is continued at a speed of 2000 rpm for 2.5 h until a uniform and fine slurry is formed;

[0092] (4) gradually adding 250 g of curing agent (polyvinyl alcohol) to the slurry prepared in step (3), and stirring for 25 min to ensure that the curing agent is evenly dispersed in the slurry to form a new slurry;

[0093] (5) The slurry obtained in step (4) was fed into a spray granulation device, the spray disk speed was adjusted to 16600 rpm, and the air inlet temperature was set to 205° C. to obtain a tin-tantalum-niobium mixed powder. The tap density of the tin-tantalum-niobium mixed powder was 1.96 g / cm 3 ;

[0094] (6) The tin-tantalum-niobium mixed powder obtained in step (5) is placed in a high-temperature furnace and annealed at 1600° C. for 4 hours to obtain an annealed powder. The tap density is increased to 3.86 g / cm 3 ;

[0095] (7) subjecting the annealed powder in step (6) to hydraulic pressure treatment, with the initial pressure set to 6 MPa, and after preliminary compaction, transferring it to a cold isostatic press and subjecting it to cold isostatic pressing at a pressure of 270 MPa to obtain a dense doped tin oxide body;

[0096] (8) The doped tin oxide blank obtained in step (7) is placed in a muffle furnace and sintered according to a complex heating and insulation procedure. First, the temperature is slowly increased to 650°C at a rate of 1°C / min and kept at this temperature for 5 hours; then, the temperature is increased to 1200°C at a rate of 2°C / min and kept at this temperature for 8 hours; then, the temperature is increased to 1500°C at a low rate of 0.5°C / min and kept at this temperature for 24 hours; oxygen is passed through the whole process, and the purity of oxygen in the oxygen-containing environment is ≥99%. Finally, the temperature is reduced to 500°C at a rate of 2°C / min, and then naturally cooled to room temperature in the furnace, so as to finally obtain a dense co-doped tin oxide material.

[0097] Example 2

[0098] The difference from Example 1 is that step (3) in Example 1 is modified as follows: Select ZnO powder with a purity of 99.99%, particle size D50 = 0.4 μm, weigh 30 g, and perform sand grinding and mixing with 150 g of the mixed powder of SnO2 and Ta2O5 in step (2) and 5000 g of water. Additionally, add 20 g of a dispersant (sodium dodecyl sulfate, methyl pentanol) to improve the powder dispersion, and add 5 g of an antifoaming agent (ethylene oxide, propylene oxide copolymer) to prevent bubble generation. The mixing process is carried out at a rotational speed of 2000 rpm for 0.5 h. Subsequently, add 3820 g of the mixed powder of SnO2 and Ta2O5, and continue sand grinding at a rotational speed of 2000 rpm for 2.5 h until a uniform and delicate slurry is formed. The remaining steps are the same as those in Example 1. The tapped density of the annealed powder obtained is 3.76 g / cm 3 。

[0099] Example 3

[0100] The difference from Example 1 is that: (1) First, carefully select SnO2 powder with a purity of 99.99%, particle size D50 = 0.4 μm, and at the same time select Sb2O3 powder with the same purity of 99.99%, particle size D50 = 0.5 μm. Subsequently, accurately weigh 500 g of SnO2 powder and 100 g of Sb2O3 powder, and 5000 g of water, and place them in a sand mill for mixing. During the mixing process, add 20 g of a dispersant (sodium dodecyl sulfate, methyl pentanol) to improve the powder dispersion, and add 5 g of an antifoaming agent (ethylene oxide, propylene oxide copolymer) to prevent bubble generation. The mixing process is carried out at a rotational speed of 2000 rpm for 0.5 h. Subsequently, add 4400 g of SnO2 powder, and continue sand grinding at a rotational speed of 2000 rpm for 2.5 h until a uniform and delicate slurry is formed;

[0101] (2) The process of spray granulation is the same as step (2) in Example 1 to obtain a mixed powder of SnO2 and Sb2O3;

[0102] (3) Select Nb2O5 powder with a purity of 99.99%, particle size D50 = 0.4 μm, weigh 100 g, and perform sand grinding and mixing with 500 g of the mixed powder of SnO2 and Sb2O3 in step (2) and 5000 g of water. Additionally, add 20 g of a dispersant (sodium dodecyl sulfate, methyl pentanol) to improve the powder dispersion, and add 5 g of an antifoaming agent (ethylene oxide, propylene oxide copolymer) to prevent bubble generation. The mixing process is carried out at a rotational speed of 2000 rpm for 0.5 h. Subsequently, add 3400 g of the mixed powder of SnO2 and Sb2O3, and continue sand grinding at a rotational speed of 2000 rpm for 2.5 h until a uniform and delicate slurry is formed;

[0103] Steps (4) to (8) are the same as those in Example 1. The tap density of the powder after annealing in Step (6) is 3.73 g / cm 3 , and finally a co-doped tin oxide material is obtained.

[0104] Comparative Example 1

[0105] The implementation steps are the same as those in Example 1, except that Ta2O5 powder is not added in Step (1), and Nb2O5 powder is not added in Step (3). Finally, a pure SnO2 target is obtained by sintering.

[0106] Comparative Example 2

[0107] The implementation steps are the same as those in Example 1, except that in Step (1), Ta2O5 powder and SnO2 powder are not milled at a mass ratio of 1:5. Instead, Ta2O5 powder and all of the SnO2 powder are directly milled. In Step (3), Nb2O5 powder and the mixed powder of Ta2O5 and SnO2 are not milled either. Finally, a tantalum-niobium co-doped SnO2 target is obtained by sintering.

[0108] Comparative Example 3

[0109] The implementation steps are the same as those in Example 1, except that the annealing treatment in Step (6) is not performed. The tap density of the tin-tantalum-niobium mixed powder is 1.96 g / cm 3 , and it is directly pressed into a green body, and finally a tantalum-niobium co-doped SnO2 target is obtained by sintering.

[0110] Comparative Example 4

[0111] The implementation steps are the same as those in Example 1, except that the final sintering temperature in Step (8) is 1550 °C, and finally a tantalum-niobium co-doped SnO2 target is obtained by sintering.

[0112] Comparative Example 5

[0113] The implementation steps are the same as those in Example 1, except that the final sintering temperature in Step (8) is 1450 °C, and finally a tantalum-niobium co-doped SnO2 target is obtained by sintering.

[0114] Application Examples 1 to 3 and Comparative Application Examples 1 to 5

[0115] The targets prepared in Examples 1 to 3 and Comparative Examples 1 to 5 are all coated into films by magnetron sputtering to obtain a transparent conductive film with a thickness of 100 nm. The magnetron sputtering conditions are as follows: a target with a diameter of 76 mm and a thickness of 2 mm is used, and sputtering is carried out by DC magnetron sputtering. The distance between the target and the substrate is set to 110 mm. During the sputtering process, the vacuum degree reaches 1.0×10 -5Pa, and the pressure during film formation is controlled at 0.5 Pa. The additive gases used include argon and oxygen, with the oxygen partial pressure being 5% of O2 / Ar. The substrate temperature is maintained at 110 °C, the sputtering power is 120 W, and the substrate material used is alkali-free glass.

[0116] Performance Test

[0117] To accurately measure the density of the targets prepared in Examples 1 to 3 and Comparative Examples 1 to 5, the Archimedes principle (also known as the buoyancy principle)-based drainage method was used to test and obtain the actual density of the targets. The relative density of the targets was obtained by comparing the measured density with the theoretical density. Using a four-probe resistance tester, by arranging four equally spaced probes on the surface of the target or film to be measured and applying a small current, the resulting voltage drop was measured. According to Ohm's law and the geometric relationship of the probe spacing, the bulk resistivity of the target was calculated; using a UV-visible-near-infrared spectrophotometer, the transmission and absorption spectra of the film were scanned within an appropriate spectral range, and its optical absorption performance was recorded. Then, the bandgap of the film was calculated by fitting using the Tauc plot method. The measured data are shown in Table 1. Figure 1 SEM morphology diagram of the polished surface of the target prepared in Example 1. Figure 2 UV absorption spectra of the targets prepared in Examples 1 to 3, which are Sample1, Sample2, and Sample3 respectively.

[0118] Table 1 Performance parameters of the targets prepared in Examples and Comparative Examples and the transparent conductive films prepared therefrom

[0119]

[0120] As can be seen from Table 1, by comparing Example 1 with Comparative Example 1, the co-doping of tantalum and niobium significantly increased the relative density of the tin oxide target, greatly reduced its bulk resistivity, and significantly enhanced its conductivity. Figure 1 This is the polished SEM morphology diagram of Example 1. It can be seen that the microstructure of Example 1 is very dense. At the same time, the broadening of the bandgap confirms the Burstein-Moss shift effect of tantalum doping, which broadens the optical bandgap. From Figure 2 It can be seen that the average transmittance of Example 1 is 85%. Turning to the comparison between Example 2 and Example 1, although the co-doping of tantalum and zinc increased the relative density and reduced the bulk resistivity, the bandgap decreased, indicating the existence of the n-type doping effect of tantalum, while the addition of zinc introduced p-type doping, resulting in a narrowing of the energy band and a decrease in the carrier concentration. The average transmittance of Example 2 is 84%. Then, comparing with Example 3, the doping of antimony increased the relative density of tin oxide and reduced the bulk resistivity, but the bandgap also narrowed, which is attributed to the self-compensation mechanism of antimony and the influence of the change in the Fermi level. The average transmittance of Example 3 is 85%.

[0121] Comparative Example 2 shows significant performance differences in the target without sanding treatment. Due to the lack of the sanding step, the distribution of dopants tantalum oxide and niobium oxide in the target becomes uneven, which directly leads to a decrease in the density of the target and an increase in the resistivity. On the other hand, Comparative Example 3 reveals the influence of the annealing treatment step on the target performance. When the raw materials without annealing treatment are directly pressed and sintered, the density of the target will significantly decrease. This is because the sintering mechanism of tin oxide requires a certain annealing process to optimize the microstructure of the powder and promote the mass transfer during sintering. The annealing treatment not only helps to remove impurities and gases in the powder, but also improves the activity of the powder, thus obtaining a denser target in the subsequent sintering process. Finally, the results of Comparative Example 4 and Comparative Example 5 jointly point out a key temperature parameter: the optimal temperature for the densification sintering of tantalum-niobium co-doped tin oxide is 1500 °C. When the sintering temperature is higher or lower than this optimal temperature, it will lead to a decrease in the density of the target. Too high a temperature may cause over-sintering or decomposition of the target, while too low a temperature is not sufficient to promote the densification process of the target. Both of these situations may lead to nodule problems on the surface of the target during the sputtering process, thereby affecting the quality and efficiency of the sputtered coating.

[0122] In summary, the following further conclusions are drawn:

[0123] (1) Tantalum-niobium co-doping effect: significantly improves the relative density of the tin oxide target, greatly reduces the bulk resistivity, significantly enhances the conductivity, broadens the optical band gap, and verifies the Burstein-Moss shift effect of tantalum doping.

[0124] (2) Tantalum-zinc co-doping effect: improves the relative density of the target and reduces the bulk resistivity; however, the band gap decreases, indicating that the addition of zinc introduces p-type doping, resulting in a narrower band gap and a decrease in the carrier concentration.

[0125] (3) Antimony-niobium co-doping effect: increases the relative density of the tin oxide target and reduces the bulk resistivity; the band gap also becomes narrower, attributed to the self-compensation mechanism of antimony and the influence of the change in the Fermi level.

[0126] (4) Pre-sanding ensures the uniform distribution of dopants, improves the density and performance of the target; annealing treatment optimizes the powder structure and promotes sintering densification; and precisely controlling the sintering temperature at 1500 °C is the key to ensuring the high quality of the tantalum-niobium co-doped tin oxide target. Deviating from this temperature will affect the density of the target and the sputtering coating effect.

[0127] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention rather than all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A co-doped tin oxide material, characterized in that, The element composition includes: tin, doped metal elements and oxygen; The doped metal elements are selected from two or more of transition metal elements, rare earth metal elements, antimony, rhenium and aluminum.

2. The co-doped tin oxide material according to claim 1, wherein The rare earth metal elements include one or more of hafnium, lanthanum, cerium and neodymium; The transition metal elements include one or more of tantalum, tungsten, titanium, molybdenum, niobium, vanadium, chromium, iron, cobalt, nickel, manganese, copper and zinc.

3. The co-doped tin oxide material according to claim 1 or 2, characterized in that, In the metal elements of the co-doped tin oxide material, the total molar percentage content of the doped metal elements < 15 mol%.

4. The co-doped tin oxide material according to claim 1, characterized in that The relative density of the co-doped tin oxide material ≥ 99%, and the volume resistivity ≤ 6 mΩ·cm.

5. The preparation method of the co-doped tin oxide material according to any one of claims 1 to 4, characterized in that, It includes the following steps: Mix SnO2 powder, doped metal element oxide powder, dispersant, defoamer and solvent, and perform sand grinding. Then, mix the obtained slurry with a curing agent for granulation to obtain doped tin oxide powder; Anneal and shape the doped tin oxide powder in sequence to obtain a doped tin oxide green body; Perform low-temperature sintering, medium-temperature sintering and high-temperature sintering on the doped tin oxide green body in sequence to obtain the co-doped tin oxide material.

6. The preparation method according to claim 5, characterized in that, The annealing treatment is carried out in an air environment; the temperature of the annealing treatment is 1200 - 1600 °C, and the holding time is 1 - 5 h.

7. The preparation method according to claim 5, characterized in that, The temperature of the low-temperature sintering is 450 - 650 °C, and the holding time is 2 - 12 h; The temperature of the medium-temperature sintering is 1000 - 1200 °C, and the holding time is 8 - 48 h; The temperature of the high-temperature sintering is 1480 - 1520 °C, and the holding time is 20 - 48 h; The whole process of low-temperature sintering, medium-temperature sintering and high-temperature sintering is carried out in an oxygen-containing environment; the purity of oxygen in the oxygen-containing environment ≥ 98%.

8. Application of the co-doped tin oxide material according to any one of claims 1 - 4 or the co-doped tin oxide material prepared by the preparation method according to any one of claims 5 - 7 in a physical vapor deposition target.

9. A transparent conductive film, characterized in that, It is formed by physical vapor deposition coating of a physical vapor deposition target on a substrate; The physical vapor deposition target is the co-doped tin oxide material according to any one of claims 1 - 4 or the co-doped tin oxide material prepared by the preparation method according to any one of claims 5 - 7.

10. The transparent conductive film according to claim 9, wherein, The thickness of the transparent conductive film is 50 - 150 nm, the sheet resistance is 1.9 - 3.5 mΩ·cm, the average transmittance is 84 - 85%, and the band gap is 3.8 - 4 eV.

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