CN106903325B

CN106903325B - Preparation method of silver-tin oxide electric contact material and electric contact material prepared by same

Info

Publication number: CN106903325B
Application number: CN201510977375.8A
Authority: CN
Inventors: 刘楠; 赖奕坚; 赵斌元
Original assignee: Schneider Electric Industries SAS
Current assignee: Schneider Electric Industries SAS
Priority date: 2015-12-23
Filing date: 2015-12-23
Publication date: 2021-01-26
Anticipated expiration: 2035-12-23
Also published as: CN106903325A

Abstract

A silver-tin oxide electric contact material and a preparation method thereof comprise the following steps: respectively preparing a reducing agent solution, a silver ammonia solution and a sodium stannate solution with certain concentrations; mixing silver ammonia solution and sodium stannate solution according to a certain proportion to form mixed solution, dripping acetic acid into the mixed solution, and adjusting the pH value of the mixed solution to form the Ag-containing solution⁺Sn (OH)₄A sol or solution; dropwise adding a reducing agent solution into Sn (OH)₄Stirring at constant temperature or performing ultrasonic-assisted reaction in the sol or solution, standing, removing supernatant, cleaning, drying, cooling, and collecting to obtain powder; carrying out heat treatment on the powder in a non-reducing atmosphere to prepare Ag-SnO₂And (3) composite powder. Thus, the particles of the composite powder can reach the nanometer level, the sintering performance is improved, and the problem of SnO in the traditional powder metallurgy process is solved₂The method has the advantages of simple preparation process, low cost, easy control of preparation conditions, short synthesis period, good product performance and the like.

Description

Preparation method of silver-tin oxide electric contact material and electric contact material prepared by same

Technical Field

The invention relates to a silver-based electric contact material used in a contactor, a relay and a switch. In particular to silver-tin oxide (Ag-SnO)₂) An electric contact material and a preparation method thereof.

Background

Generally, the electric contact material is a silver-based electric contact material, and because the silver-based electric contact material has better electric wear resistance, fusion welding resistance, excellent conductivity and stable and relatively small contact resistance, the silver-based electric contact material is widely applied to various light and heavy load electric appliances, household appliances, automobile electric appliance parts and aerospace electric appliance parts, and is one of the most common electric contact materials.

In particular, Ag-MeO is widely used in various low voltage appliances ranging from several volts to several kilovolts, with the current applied from several tens of amperes to several thousands of amperes. Ag-CdO is widely applied to middle-load electric appliances due to the excellent fusion welding resistance, electric wear resistance and lower contact resistance, and is called a universal contact, but because cadmium toxicity is generated in the process of manufacturing and using the Ag-CdO material, Ag-CdO electric contact materials are forbidden or limited in some countries and regions. An important development direction of silver-based electrical contact materials is to develop new materials capable of replacing Ag-CdO due to the requirement of environmental protection.

Furthermore, Ag-SnO₂The electric contact material is a novel non-toxic electric contact material which develops rapidly in recent years, has the common characteristics of common Ag-MeO materials, also has stronger electric arc erosion resistance, fusion welding resistance and thermal stability, has the use range of 10-1000A, and is one of the most main environment-friendly electric contact materials for replacing Ag-CdO in contactors, relays and switches.

Thus, the production of Ag-SnO₂There are various methods of electrically contacting the material. At present, the alloy internal oxidation method and the powder metallurgy method are Ag-SnO which have wider industrial application₂A preparation process of the electric contact material. The material prepared by the alloy internal oxidation method has a fine grain structure, and has high strength, hardness, arc ablation resistance and fusion welding resistance, but the material prepared by the method has an uneven structure, and is easy to have poor oxide zones, oxide aggregation, inclusion, pores and other structure defects. The powder metallurgy method mainly adopts mechanical mixing in the preparation stage of raw material powder, such as a mechanical alloying method, the powder mixing process is adopted, the equipment is simple, the silver powder and the tin oxide powder are mechanically mixed, additives of different types and different amounts can be added at will, the components of the alloy can be adjusted in a large range, the material tissue structure is uniform, no poor metal oxide area exists, if the powder mixing time is not well controlled, the surface condition or particle distribution of the powder is easy to change, the component segregation processing hardening and the like are caused, the finally prepared material has low density, the particle size of the tin oxide powder is generally 3-5 cm thick, the contact resistance of a contact is large, the temperature is increased, the arc ablation resistance is poor, and the electrical life of the contact is influenced.

Disclosure of Invention

The invention mainly aims to provide Ag-SnO₂Method for preparing electric contact material and Ag-SnO₂Electric contact material of Ag-SnO₂The preparation method of the electric contact material is to prepare Ag-SnO by adopting an in-situ synthesis liquid phase reduction method₂The nano powder replaces the physical powder mixing process by chemical compounding, thereby realizing SnO₂More uniform mixing with Ag and simultaneously improved SnO₂Wettability with Ag.

To achieve the above object, the present invention provides an Ag-SnO₂A method for preparing an electrical contact material, the method comprising the steps of:

(1) respectively preparing a reducing agent solution, a silver ammonia solution and a sodium stannate solution with certain concentrations;

(2) mixing the silver ammonia solution and the sodium stannate solution according to a certain proportion to form a mixed solution, dripping acetic acid into the mixed solution, and adjusting the pH value of the mixed solution to form Sn (OH)₄A sol or solution;

(3) dropwise adding a reducing agent solution into the Sn (OH) obtained in the step (2)₄Stirring at constant temperature or performing ultrasonic-assisted reaction in the sol or solution, standing, removing supernatant, cleaning, drying, cooling, and collecting to obtain powder;

(4) carrying out heat treatment on the powder collected in the step (3) in a non-reducing atmosphere to prepare Ag-SnO₂And (3) composite powder.

The invention also provides Ag-SnO prepared by the preparation method₂An electrical contact material.

The present invention also provides a silver-tin oxide electrical contact material, wherein the silver-tin oxide electrical contact material comprises Ag particles and SnO₂Particles of, wherein the SnO₂The particles are uniformly coated on the surface of the Ag particles to obtain uniform Ag-SnO₂And (3) composite powder.

Drawings

FIG. 1 shows Ag-SnO according to the present invention₂A flow chart of a method of making an electrical contact material;

FIG. 2 shows Ag-SnO prepared by the preparation method of the invention₂Scanning Electron Microscope (SEM) images of the product;

FIG. 3 is a graph of energy spectrum analysis (EDS) of FIG. 2;

FIG. 4 shows Ag-SnO prepared by the preparation method of the invention₂Transmission Electron Microscopy (TEM) images of the product;

FIG. 5A shows conventional Ag-SnO₂The effect of the sample arcing energy is shown schematically; (ii) a

FIG. 5B is an Ag-SnO alloy of the present invention₂The effect of the sample arcing energy is shown schematically;

FIG. 6A shows conventional Ag-SnO₂The effect schematic diagram of the starting arcing time of the sample;

FIG. 6B is an Ag-SnO alloy of the present invention₂The effect schematic diagram of the starting arcing time of the sample;

Detailed Description

Ag-SnO₂The current preparation methods of the materials are as follows: preparing sol solution of stannous chloride dihydrate, adding silver nitrate solution, adjusting pH value to control Sn₂ ⁺Sol particles and Ag⁺Ion in-situ chemical reaction to prepare the Ag-SnO₂Composite particles of SnO₂The content is higher by 10-90%, and the silver powder is mixed with pure silver powder to reduce SnO₂The content of the composite material is 5-30%, and then the electric contact composite material is obtained through pressing, sintering and hot extrusion. The method inevitably generates a part of silver chloride precipitate to cause impurity content of the final contact product, and the Ag-SnO prepared by the method₂SnO in composite particles₂The higher content of the silver powder is also needed to reduce SnO₂Not only the preparation process is increased, but also the added silver powder and Ag-SnO₂The problem of uneven mixing is easily formed.

Therefore, the invention creates Ag-SnO₂The preparation method mainly prepares the mixed powder with small size of the added phase particles and uniform dispersion distribution by nano-scale compounding. Namely: fully mixing a silver-containing precursor solution (namely silver ammonia solution) and a tin oxide precursor solution (namely sodium stannate solution), preparing silver powder with the surface coated with a nano tin oxide precursor by adopting an in-situ synthesis liquid phase reduction method, then converting the tin oxide precursor into nano-scale powder of tin oxide through heat treatment such as drying, calcining and the like, growing nuclei on corresponding positions on the surface of the silver powder, successfully coating nano-scale silver powder particles, achieving the aim of nano-scale compounding-conversion, and improving Ag and SnO₂The wettability of (2).

Specifically, please refer to FIG. 1, the Ag-SnO of the present invention₂The manufacturing method of the electric contact material mainly comprises the following steps:

(2) mixing the silver ammonia solution and the sodium stannate solution according to a certain proportion to form a mixed solution, dripping acetic acid into the mixed solution, and adjusting the pH value of the mixed solution to form the Ag-containing solution⁺Sn (OH)₄A sol or solution;

(3) dropwise adding a reducing agent solution into the Sn (OH) obtained in the step (2)₄Stirring at constant temperature or performing ultrasonic-assisted reaction in the sol, standing, removing supernatant, cleaning, drying, cooling, and collecting to obtain powder;

Wherein the reducing agent can be one or more selected from formaldehyde, glyoxal, ethylenediamine, glucose, potassium sodium tartrate, sodium citrate, hydrazine hydrate, vitamin C, sodium borohydride or ascorbic acid. The concentration of the reducing agent solution, the silver-containing concentration of the silver-ammonia solution and the concentration of the sodium stannate solution are respectively as follows: 10 to 2000ppm, 10 to 2000 ppm.

The mixing ratio of the silver ammonia solution and the sodium stannate solution in the step (2) is 4-20: 1 in terms of the mass ratio of silver in the silver ammonia solution to tin dioxide in the sodium stannate solution, and the pH value is adjusted to be 0.5-11.

The reaction temperature in the step (3) is 10-40 ℃, and the reaction time is 1-24 hours.

The non-reducing atmosphere includes an inert atmosphere or an oxidizing atmosphere. The oxidizing atmosphere is oxygen or air or other oxygen-containing atmosphere. The inert atmosphere comprises nitrogen and a noble gas. The rare gas may be at least one of argon, helium and neon.

The heat treatment process can be selected within the range of roasting for 1-12 h at the temperature of 150-800 ℃.

The silver-metal oxide electric contact material is selected according to the range, so that the mass percentage of the silver in the silver-metal oxide electric contact material can reach 86-99.5%.

In combination with the above, the present invention further discloses the following specific embodiments:

example 1

(1) Respectively preparing a hydrazine hydrate solution with the concentration of 10ppm, a silver ammonia solution with the concentration of 50ppm and a sodium stannate solution with the concentration of 1000 ppm;

(2) mixing the silver ammonia solution and the sodium stannate solution according to a mixing ratio of silver to stannic oxide of 4: 1, adding acetic acid dropwise into the mixed solution to adjust the pH value of the mixed solution to 3.5 to form Ag-containing solution⁺Sn (OH)₄Sol;

(3) dropwise adding a hydrazine hydrate solution into the Sn (OH) obtained in the step (2)₄Stirring and reacting in the sol at a constant temperature of 10 ℃ for 1h, standing, removing supernatant, cleaning, drying, cooling and collecting to obtain powder;

(4) roasting the powder collected in the step (3) for 5 hours at 300 ℃ in a nitrogen atmosphere to prepare Ag-SnO₂And (3) composite powder.

Example 2

(1) Respectively preparing an ascorbic acid solution with the concentration of 200ppm, a silver ammonia solution with the concentration of 10ppm and a sodium stannate solution with the concentration of 10 ppm;

(2) mixing the silver ammonia solution and the sodium stannate solution at a ratio of 10:1 (calculated as silver and stannic oxide) to form a mixed solution, and dropwise adding acetic acid into the mixed solution to adjust the pH value of the mixed solution to 0.5 to form a solution containing Ag⁺Sn (OH)₄Sol;

(3) dripping ascorbic acid solution into the Sn (OH)4 sol obtained in the step (2), stirring and reacting at the constant temperature of 25 ℃ for 2h, standing, removing supernatant, cleaning, drying, cooling and collecting to obtain powder;

(4) roasting the powder collected in the step (3) for 12 hours at 150 ℃ in air atmosphere to prepare Ag-SnO₂And (3) composite powder.

Example 3

(1) Respectively preparing an ascorbic acid solution with the concentration of 100ppm, a silver ammonia solution with the concentration of 100ppm and a sodium stannate solution with the concentration of 100 ppm;

(2) mixing the silver ammonia solution and the sodium stannate solution according to the mixing ratio of silver to stannic oxide of 7.3:1 to form a mixtureAdding acetic acid dropwise into the mixture to adjust pH to 2.0 to obtain Sn (OH)₄Sol; (attention is paid here to the nature of the tin hydroxide, amphoteric, Sn (OH)₂Basic group, Sn (OH)₄Mainly acidic, and tin hydroxide and stannous hydroxide can react and dissolve when meeting strong base to respectively generate stannate and stannous chloride. Because of the nature of tin hydroxide, it is not a tin hydroxide sol at higher pH, and thus the pH can be written as acidic, as in the other examples. The results understood at present show that a pH of between 0.5 and 1 is a good sol)

(3) Dropwise adding ascorbic acid solution into Sn (OH) obtained in the step (2)₄Stirring and reacting in the sol at a constant temperature of 25 ℃ for 6 hours, standing, removing supernatant, cleaning, drying, cooling and collecting to obtain powder;

(4) roasting the powder collected in the step (3) for 3 hours at 550 ℃ in a nitrogen atmosphere to prepare Ag-SnO₂And (3) composite powder.

Example 4

(1) Respectively preparing a sodium citrate solution with the concentration of 150ppm, a silver ammonia solution with the concentration of 500ppm and a sodium stannate solution with the concentration of 50 ppm;

(2) mixing the silver ammonia solution and the sodium stannate solution according to the mixing ratio of silver to tin dioxide of 20:1 to form a mixed solution, and dripping acetic acid into the mixed solution to adjust the pH value of the mixed solution to 11 to form the solution containing Ag⁺Sn (OH)₄A solution;

(3) dropwise adding the sodium citrate solution into the Sn (OH) obtained in the step (2)₄Stirring and reacting the solution at the constant temperature of 40 ℃ for 2 hours, standing the solution, removing supernatant, cleaning, drying, cooling and collecting powder;

(4) roasting the powder collected in the step (3) for 5 hours at 700 ℃ in a mixed atmosphere of nitrogen and helium to prepare Ag-SnO₂And (3) composite powder.

Example 5

(1) Respectively preparing a vitamin C solution with the concentration of 2000ppm, a silver ammonia solution with the concentration of 600ppm and a sodium stannate solution with the concentration of 100 ppm;

(2) adding silver ammoniaThe mixing ratio of the solution and the sodium stannate solution is 12 in terms of silver and stannic oxide: 1, adding acetic acid dropwise into the mixed solution to adjust the pH value of the mixed solution to 8.5 to form Ag-containing solution⁺Sn (OH)₄A solution;

(3) dropwise adding the vitamin C solution into the Sn (OH) obtained in the step (2)₄Stirring and reacting the solution at the constant temperature of 20 ℃ for 12 hours, standing the solution, removing supernatant, cleaning, drying, cooling and collecting powder;

(4) roasting the powder collected in the step (3) for 6 hours at 450 ℃ in a nitrogen atmosphere to prepare Ag-SnO₂And (3) composite powder.

Example 6

(1) Respectively preparing an ascorbic acid solution with the concentration of 500ppm, a silver ammonia solution with the concentration of 2000ppm and a sodium stannate solution with the concentration of 2000 ppm;

(2) mixing silver ammonia solution and sodium stannate solution at a ratio of silver to tin dioxide of 15:1 to form a mixed solution, and dripping acetic acid into the mixed solution to adjust the pH value of the mixed solution to 5.5 to form the solution containing Ag⁺Sn (OH)₄Sol;

(3) dropwise adding ascorbic acid solution into Sn (OH) obtained in the step (2)₄Stirring and reacting in the sol at a constant temperature of 25 ℃ for 20 hours, standing, removing supernatant, cleaning, drying, cooling and collecting to obtain powder;

(4) roasting the powder collected in the step (3) for 1h at 800 ℃ in a mixed atmosphere of nitrogen and argon to prepare Ag-SnO₂And (3) composite powder.

Example 7

(1) Respectively preparing a glucose solution with the concentration of 1500ppm, a silver ammonia solution with the concentration of 1200ppm and a sodium stannate solution with the concentration of 1000 ppm;

(2) mixing the silver ammonia solution and the sodium stannate solution according to the mixing ratio of silver to stannic oxide of 6: 1, adding acetic acid dropwise into the mixture to adjust the pH value of the mixture to 3.5 to form Ag-containing solution⁺Sn (OH)₄Sol;

(3) dropwise adding a glucose solution to the Sn (OH) obtained in the step (2)₄Sol gelStirring and reacting at a constant temperature of 10 ℃ for 24 hours, standing, removing supernatant, cleaning, drying, cooling and collecting to obtain powder;

(4) roasting the powder collected in the step (3) for 4 hours at 600 ℃ in a nitrogen atmosphere to prepare Ag-SnO₂And (3) composite powder.

Referring to fig. 2, 3 and 4, the silver-tin oxide electrical contact material of the present invention mainly comprises Ag particles and SnO₂Particles of, wherein the SnO₂The particles are uniformly coated on the surface of the Ag particles to obtain uniform Ag-SnO₂And (3) composite powder. And SnO coated around Ag particles₂In the form of rod and granule.

The SnO₂The coating rate of the particles coating the surface of the Ag particles is 10-100%, preferably more than 90%.

The Ag and SnO₂And coated with SnO₂The Ag particles are nano-scale SnO₂The particle size of (A) may be up to about 5-100nm, preferably about 50 nm.

The preferable mixture ratio of the silver-tin oxide electric contact material is that the content of Ag is 88.10%, the content of Sn is 9.37%, and the content of O is 2.53%.

The mass percentage of silver in the silver-tin oxide electric contact material is 86-99.5%.

In the silver-tin oxide electrical contact material, SnO₂The content of (A) is 0.5-14%. General SnO₂The content of (B) is 12%.

The Ag-SnO prepared by the preparation method₂The composite powder product has the following characteristics:

please refer to fig. 2 and fig. 3 in detail, fig. 2 shows the Ag-SnO prepared by the preparation method of the present invention₂Scanning Electron Microscope (SEM) image of the product, FIG. 3 is an energy spectrum analysis (EDS) image of FIG. 2, so that it can be seen that the coated SnO of the present invention₂The Ag particles of the Ag-Ag alloy are uniform in size and are all nano-scale, wherein when the total amount of the Ag-Ag alloy particles is 100 units, the preferable mixture ratio is that the content of Ag element is 88.10%, the content of Sn element is 9.37%, and the content of O element is 2.53%, and then the high ratio can be obtainedExample Ag-SnO₂A material.

Please refer to fig. 4, which shows the Ag-SnO prepared by the preparation method of the present invention₂The Transmission Electron Microscope (TEM) image of the product shows that the product contains two phases of silver and tin dioxide at the same time through XRD, and the TEM result shows that darker granular substances in the image 4 are single Ag and SnO₂The Ag particles are distributed around the Ag particles in a rod shape and a particle shape, and are in a nanometer size.

The above Ag-SnO₂The material can be obtained through an arc burning experiment, and the comparison of the invention and the prior art can show that the Ag-SnO of the invention₂As shown in FIGS. 5A and 5B, the material has excellent properties, and FIG. 5A shows conventional Ag-SnO₂Schematic representation of the arcing energy of the sample, where it can be seen that the existing AgSnO₂The arc burning energy of the sample rises along with the increase of the action times; and FIG. 5B is an Ag-SnO according to the present invention₂In the schematic diagram of the effect of the sample arcing energy, it can be seen that the AgSnO provided by the invention₂The arcing energy of the sample does not change obviously along with the increase of the action times, and the average arcing energy of 2 ten thousand times is lower than that of the conventional AgSnO₂Half of the sample.

Referring to fig. 6A and 6B, fig. 6A is a schematic diagram of conventional Ag — SnO₂Effect diagram of the time of starting arcing of the sample, which shows the presence of Ag-SnO₂The sample is increased along with the increase of the action times, and the starting arcing time is increased; FIG. 6B shows Ag-SnO of the present invention₂The effect of the time for starting the arc combustion of the sample is shown in the figure, wherein the AgSnO of the invention is shown₂The sample has no obvious change in the starting arcing time along with the increase of the action times, and the average arcing time of 2 ten thousand times is obviously lower than that of the conventional AgSnO2 sample.

As can be seen from this, Ag-SnO obtained by the production method of the present invention₂Is a better electric contact material, and the product performance is better.

The invention is due to Ag-SnO₂SnO in electric contact material₂The particles reach the nano scale, so the method has strong dispersion strengthening effect and obviously enhances the strength and the hardness of the silver matrix material. In addition, it is expected that the addition of the contact material will occur due to the unique small size effect of the nanoparticlesThe ratio of the mechanical property, the electrical conductivity, the corrosion resistance and the fusion welding resistance is micron Ag-SnO₂The electrical contact material is significantly improved. Ag-SnO₂The material is Ag-based or SnO₂The particles are dispersed metal matrix composite materials of strengthening phase. Since in most cases SnO₂The particle size is 0.5-1 μm, the particle strengthening and dispersion strengthening action mechanisms exist simultaneously, and the finer the particles, the higher the volume fraction, the better the strengthening effect of the particles on the composite material, and the higher the strength of the material.

The invention uses an in-situ synthesis liquid phase reduction method to obtain the silver powder with a layer of nano SnO uniformly coated on the surface₂Obtaining uniform Ag-SnO₂Composite powder for reducing SnO₂Increase the particle size of SnO₂The wettability with Ag powder improves the processing performance and the service performance of the Ag-SnO composite powder as a contact material, and Ag and SnO in the composite powder₂The proportion is easy to regulate and control.

In conclusion, the invention adopts an in-situ synthesis process, and silver-ammonia solution and Na are used₂SnO₃The silver ion-containing silver ion and Sn (OH) are used as starting materials, both of which are alkaline substances, can be uniformly mixed in an aqueous solution to form a mixed solution, and the pH value of the mixed solution is adjusted to realize the purpose of containing silver ions and Sn (OH)₄Homogeneous dispersion of the sol in Sn (OH)₄Silver powder is obtained in the sol through the action of a reducing agent, the surface of the silver powder is clean and has larger surface activity, the granularity of the silver powder is smaller, and the silver powder has larger specific surface area, so that Sn (OH)₄The particles can be effectively adsorbed on the surface of the silver powder and coated and mixed with the silver powder.

In addition, the in situ synthesis method of the present invention simultaneously produces silver powder and the Sn (OH) precursor of the additive phase₄Two kinds of precipitates, wherein the precipitates are subjected to heat treatment such as drying, calcining and the like to convert a tin oxide precursor into nanoscale powder of tin oxide, and nucleation is grown at corresponding positions on the surface of the silver powder, so that nanoscale silver powder particles are successfully coated, the aim of nanoscale compounding-conversion is fulfilled, and Ag and SnO are improved₂The wettability of (2). The material prepared by the method has low impurity content, wherein the contents of Bi, Sb, As and Pb are not more than 0.003 percent, and the total impurity content is not more than 0.1 percent.

Meanwhile, the SnO can be reduced by the method₂Increase the particle size of SnO₂Wettability with Ag powder, and uniformly coating a layer of nano SnO on the surface of the silver powder₂The particles are uniformly obtained to obtain Ag-SnO₂Composite powder, and Ag and SnO in the composite powder₂The proportion is easy to regulate and control, and the processing performance and the service performance of the contact material are improved. The invention refines the particles, improves the sintering property of the material, and solves the problem of SnO existing in the traditional powder metallurgy process₂The method has the advantages of simple preparation process, low cost, easy control of preparation conditions, short synthesis period, good product performance and the like.

Although the present invention has been described with reference to the above embodiments, it should be understood that the invention is not limited thereto, and that various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. The preparation method of the silver-tin oxide electric contact material is characterized by comprising the following steps of:

(2) mixing the silver ammonia solution and the sodium stannate solution according to a certain proportion to form a mixed solution, dripping acetic acid into the mixed solution, and adjusting the pH value of the mixed solution to form the solution containing Ag⁺Sn (OH)₄A sol or solution;

2. The method for preparing a silver-tin oxide electrical contact material according to claim 1, wherein the reducing agent is one or more of formaldehyde, glyoxal, ethylenediamine, glucose, sodium potassium tartrate, sodium citrate, hydrazine hydrate, vitamin C, sodium borohydride, or ascorbic acid.

3. The method for preparing the silver-tin oxide electrical contact material according to claim 1, wherein the concentration of the reducing agent solution, the silver-containing concentration of the silver ammonia solution, and the concentration of the sodium stannate solution are respectively: 10 to 2000ppm, 10 to 2000 ppm.

4. The method for preparing the silver-tin oxide electrical contact material according to claim 1, wherein the mixing ratio of the silver ammonia solution to the sodium stannate solution in the step (2) is 4-20: 1 in terms of the mass ratio of silver in the silver ammonia solution to tin dioxide in the sodium stannate solution, and the pH value is adjusted to be 0.5-11.

5. The method for preparing the silver-tin oxide electrical contact material according to claim 1, wherein the reaction temperature in the step (3) is 10-40 ℃ and the reaction time is 1-24 hours.

6. The method for preparing a silver-tin oxide electrical contact material according to claim 1, wherein the non-reducing atmosphere comprises an inert atmosphere or an oxidizing atmosphere.

7. The method for preparing a silver-tin oxide electrical contact material according to claim 6, wherein the oxidizing atmosphere is oxygen or air.

8. The method for preparing a silver-tin oxide electrical contact material according to claim 6, wherein the inert atmosphere contains nitrogen and/or a rare gas.

9. The method of producing a silver-tin oxide electrical contact material according to claim 8, wherein the rare gas is at least one of argon, helium, and neon.

10. The method for preparing the silver-tin oxide electrical contact material according to claim 1, wherein the heat treatment process is roasting at 150-800 ℃ for 1-12 h.

11. The method for preparing the silver-tin oxide electrical contact material according to claim 1, wherein the mass percent of silver in the silver-tin oxide electrical contact material is 86-99.5%.

12. A silver-tin oxide electrical contact material produced by the method for producing a silver-tin oxide electrical contact material according to any one of claims 1 to 11.

13. The silver-tin oxide electrical contact material of claim 12, wherein the silver-tin oxide electrical contact material comprises Ag particles and SnO₂Particles of the SnO₂The particles are uniformly coated on the surface of the Ag particles to obtain uniform Ag-SnO₂And (3) composite powder.

14. The silver-tin oxide electrical contact material of claim 13, wherein the SnO is coated around the Ag particles₂In the form of rod and granule.

15. The silver-tin oxide electrical contact material of claim 13, wherein each is coated with SnO₂The Ag particles are uniform in size.

16. The silver-tin oxide electrical contact material of claim 15, wherein the SnO₂Is of nanometer size.

17. The silver-tin oxide electrical contact material of claim 13, wherein the SnO₂The coating rate of the particles coated on the surface of the Ag particles is 10-100%.

18. The silver-tin oxide electrode of claim 13A contact material, wherein in the silver-tin oxide electrical contact material, SnO₂The content of (A) is 0.5-14%.