WO2016192049A1 - Fine tantalum powder and manufacturing method thereof - Google Patents

Abstract

Provided is a fine tantalum powder. The fine tantalum powder has a D50 < 5 µm, preferably a D50 < 4.5 µm, and an apparent density of 2.0-6.0 g/cm³, preferably 2.2-4.5 g/cm³. Also provided is a method for manufacturing the fine tantalum powder, comprising: 1) providing a sodium reduced tantalum powder as a raw material; 2) sintering the raw material with a high temperature to obtain a sintered block; 3) performing hydrogen decrepitation of the sintered block to obtain a hydrogenated tantalum powder; and 4) dehydrogenating, deoxygenating, pickling, drying and sifting the hydrogenated tantalum powder.

Description

Microfine powder and preparation method thereof Technical field

The invention relates to the field of rare metal smelting, relates to the processing technology of bismuth powder, and in particular to a method for preparing fine bismuth powder.

Background technique

In recent years, semiconductor technology has developed rapidly and various electronic devices have been developed. Semiconductor technology requires miniaturization of electronic devices to increase integration, and a thin film formation process is required in many processes. The demand for ruthenium as a sputter film has also increased correspondingly, especially as a diffusion barrier between silicon and copper conductors in integrated circuits. The production method of the sputtering target includes an ingot metallurgy method (I/M method) and a powder metallurgy method (P/M method). Commonly used targets are generally made of bismuth ingots. However, in some special cases (such as high requirements), the I/M method cannot be used, and only powder metallurgy can be used as a target. For example, a silicon germanium alloy target cannot be used because of the difference in melting point of germanium and silicon and the low toughness of the silicon compound. Compared with the I/M method, the P/M method can not make the grain size thinner, so the raw materials used at the beginning need to have the desired grain size, and the more uniform and finer the grains in the target are obtained. The more uniform the film. The performance of the target directly affects the performance of the sputtered film, and for low-density targets, various problems inevitably occur during sputtering. For example, the cluster of particles scattered from the sputtering target is attached to the substrate, which is a cause of major problems such as disconnection of the wiring loop on the substrate. If the density of the target is increased, the particles are greatly reduced during sputtering, and in order to increase the density of the target, the raw material 钽 powder should have a fine particle size and a high bulk density.

In general, refractory metals are difficult to sinter to very high densities. In order to increase the density of sintered bodies, a common method is to press the metal powder into a jacket under pressure sintering, and then carry the powder-coated jacket. Sintering, which is important for the loading conditions of the raw material powder. In the case of hot isostatic pressing, increasing the packing density can increase the density of the sintered body, can reduce irregular shrinkage during sintering, generate less cracks, and improve the yield. In other words, when pressure sintering is performed, it is important that the raw material powder is densely packed and uniform. It is well known that for sodium-reduced coral-like tantalum powder, the smaller the particle size, the smaller the corresponding bulk density. For bombardment In the case of ingot hydrogenation of crucible powder, it is difficult to achieve a small average particle size in actual production.

For example, the tantalum powder disclosed in the Chinese patents CN102909365A and CN103447544A is obtained by crushing and classifying a hydrogenated tantalum ingot, and has a D50 of >10 μm. Since the bombardment of the ingot is used as the raw material, the obtained powder particles have a dense spherical shape, and it is difficult to further refine the particle size, and the production cost is greatly improved.

A method for making a tantalum powder into a certain size is disclosed in the patent CN1223695A, "Method for Producing Size-Controllable Base Metal Powder and Product Made by the Method", filed by Cabot Corporation. The base powder of the crucible consisting of a substantial portion of the agglomerates of particles comprising a single powder is comminuted to form an intermediate product having a size of from 0.01 to 20 μm. However, the tantalum powder manufactured by the patented technology is used for the production of anode blocks for tantalum electrolytic capacitors. Since the anode block of the tantalum electrolytic capacitor requires a porous structure, it is desirable to have a porous structure as large as possible, and the structure has a small bulk density, generally less than 2.0 g/cm ³ . At the same time, since it has not been subjected to high temperature treatment, impurities such as K and Na which are carried in the sodium reduction process are high. In a semiconductor device, an alkali metal such as K or Na has a bad influence on the interface property of a metal-oxide-semiconductor (MOS). Since the final product is used for the production of capacitor electrodes, it is required that the powder has good fluidity, and at the same time, the powder particles have large pores inside, so that the capacitor made thereof has good electrical properties, so the patent selects the intermediate product. With a higher heat treatment temperature (greater than 1200 ° C) treatment, the particle size of the final product is significantly increased, D50> 100 μm, which is not suitable for sputtering targets.

Further, in consideration of the treatment method, the cerium powder after sodium reduction is directly pulverized without being subjected to high temperature treatment. As the sodium reduction technique described in the patent, the size distribution of the tantalum powder is broad and polydisperse, which results in the presence of some ultrafine powder particles ("ultrafine particles" refers to particles having a particle size of less than 100 nm) due to their activity. High, it is easy to occur in the process of powdering and burning, there is a certain safety hazard.

In summary, as the sputtering film has a requirement for the particle size of the raw material powder to be refined and homogenized, the production process of the conventional tantalum powder can no longer meet the production requirements.

Summary of the invention

It is an object of the present invention to overcome one or more of the above disadvantages and to provide a better performance tantalum powder and a method of producing the same.

The present invention provides a fine bismuth powder characterized by an average particle diameter D50 < 5 μm, preferably D50 < 4.5 μm, and a bulk density of 2-6 g/cm ³ , preferably 2.2-4.5 g/cm ³ .

Preferably, the niobium powder has a K+Na content of not more than 20 ppm, preferably not more than 15 ppm, more preferably not more than 10 ppm; optionally an oxygen content of not more than 6000 ppm, preferably not more than 4000 ppm, more preferably not more than 3500ppm.

In particular, in order to reduce the risk of powder fire during processing, the present invention provides a method of producing the powder. Specifically, the method includes:

1) providing powdered raw materials;

2) sintering the raw material at a high temperature to obtain a sintered block;

3) hydrocracking the agglomerate to obtain hydrogenated tantalum powder (ie, hydrogenated tantalum powder);

4) Dehydrogenation, oxygenation, pickling, drying and sieving of the hydrogenated tantalum powder.

Preferably, the high temperature sintering is carried out under high vacuum conditions, for example, 10 ^-2 -10 ^-5 Pa, preferably about 10 ^-3 Pa.

Preferably, the sintering temperature of the high-temperature sintering is 1400 to 2000 ° C, and preferably, the holding time at the sintering temperature is 1-5 hours, preferably 2-3 hours.

The powdered raw material may be, for example, derived from waste tantalum powder recovered during the production of tantalum powder for capacitors, or may be specially produced tantalum powder, for example, sodium reduced tantalum powder. It should be understood that tantalum powder for capacitors is also generally produced by sodium reduction.

It should be understood that the sodium reduced niobium powder refers to the tantalum powder obtained by the process of reducing sodium fluoroantimonate by sodium metal, which is one of the most commonly used processes for preparing tantalum powder. In the present invention, if the waste tantalum powder produced in the production process of the tantalum powder for capacitors is used, in particular, the waste tantalum powder is produced as a raw material in the production process of the high specific volume tantalum powder for capacitors, the production cost can be remarkably reduced.

In the present invention, the high-temperature sintering is performed by heating the raw material tantalum powder to a vacuum (a vacuum degree of generally 10 ^-2 Pa - 10 ^-5 Pa, preferably about 10 ^-3 Pa) to 1200-2000 ° C (for example, 1400). °C, 1500 ° C, 1800 ° C) 1-5 hours (for example, 2 hours, 3 hours, 4 hours), after the end of sintering, cooling, passivation treatment to obtain a bismuth agglomerate.

A temperature of 1200-2000 ° C is preferred because it can avoid the adhesion of tantalum powder and niobium sintering which may be caused by excessive heat treatment temperature, resulting in difficulty in peeling, increasing labor intensity, reducing niobium service life, increasing cost, and It is not necessary to avoid partial ultrafine particle agglomeration which may be caused by too low heat treatment temperature. During the crushing process, some ultra-fine powders with higher activity are re-agglomerated, which is not conducive to micro-fine grinding or loss of ignition materials.

The hydrocracking in the step 3) means that the agglomerate obtained in the step 2) is heated and hydrogen is absorbed to obtain a crucible having good hydrogen embrittlement, and then the powder is crushed by a mechanical method to obtain a crucible powder which can pass through a 100 mesh sieve. It is then preferably further crushed by methods such as ball milling, impact, extrusion, etc. to further reduce the particle size, for example to a D50 < 5 μm. Optionally, the tantalum powder is also pickled (for example with a mixed acid of HNO ₃ and HF) to remove metallic impurities.

There is no restriction on the hydrogen content of the hydrogenated clam block. However, it has been unexpectedly found that it is preferred if the hydrogen content of the ruthenium block after hydrogenation is not less than 4,000 ppm. Because if the hydrogen content is too low, although the object of the present invention can also be achieved, the hydrogen embrittlement is not good enough, and it is difficult to perform fine crushing during the ball mill crushing process, and it becomes flat flat powder because of its ductility. The control of the D50 is unfavorable.

The crushing method in the hydrogenation crushing process is preferably performed by mechanically breaking up to pass through a 100 mesh sieve, using a wet agitating ball mill, for example, using zirconia balls as a ball milling medium, water or an organic solvent as a dispersion medium, and continuously ball milling until D50 < 5 μm. . It has been found that a ball milling time of 0.5-4 h (e.g., 1-3 h) can satisfactorily achieve a D50 &lt; 5 m. Due to the high hardness of the hydrogenated tantalum powder, the use of ordinary stainless steel ball grinding causes severe wear on the stainless steel ball, and a large amount of metal impurities are mixed into the material, resulting in a high impurity content. In order to improve the purity of the final product, it is preferred to use a higher hardness zirconia ball instead of a stainless steel ball for grinding.

In order to obtain a finer and more uniform particle size distribution, a smaller grinding medium ball is used for the grinding. The reason is that the grinding medium with a small diameter has a large filling amount in the grinding chamber, which increases the impact and friction of the grinding medium, increases the contact area of the grinding medium, and increases the grinding area, which also contributes to fine pulverization. It has been unexpectedly found that a grinding ball having a diameter of from 1 to 5 mm, preferably from 2 to 4 mm, can achieve a better grinding effect.

The present invention requires a product having a finer particle size (D50 < 5 μm), but it may be difficult to avoid the production of ultrafine powders having a particle size of less than 0.1 μm during ball milling, which are often susceptible to oxidation or even spontaneous combustion, which seriously affects the performance of the powder, resulting in production failure. At the same time, due to the finer particle size of the powder, the larger the surface area, the larger the surface free energy, resulting in re-agglomeration of the particles, which is not conducive to micro-fine grinding. For the purpose of facilitating pulverization, it is preferred to add a surfactant as a grinding aid to the dispersion medium. Because the surfactant can adhere to the surface of the tantalum powder particles to form a protective layer, the material particles can be surface passivated while miniaturizing the ball mill, which can effectively inhibit the oxidation of the ultrafine powder during ball milling and subsequent processing, and ensure the product. quality. Preferred grinding aids are butanone and/or isopropanol. More preferably, the grinding aid is added in an amount of from 0.5 to 5%, preferably from 1 to 4%, more preferably from 1.8 to 3.6% by weight of the niobium powder.

The dehydrogenation and oxygen reduction used in the present invention may be conventional dehydrogenation and oxygen reduction. For example, it can be carried out by generally adding a small amount of a reducing agent having an affinity for oxygen to the affinity of oxygen, such as an alkaline earth metal, a rare earth metal and a hydride thereof, in the tantalum powder, and the most common one is in the tantalum powder. Mixing metal magnesium powder with 0.2-6.0% by weight of niobium powder, heating under vacuum or inert gas protection (preferably inert gas), holding at 800-900 ° C for 1-3 hours, then vacuuming, then Heat for 2-6 hours under vacuum. Then, the temperature is lowered and passivated to obtain a powder containing no hydrogen.

It should be understood that pickling and decontamination can reduce impurities such as oxygen, carbon, iron, nickel, chromium, and the like in the tantalum powder. For example, the tantalum powder can be pickled by mixing with 10% by mass of HNO ₃ , the solid-liquid ratio of tantalum powder to HNO ₃ is 1:1, and stirring for 10-90 minutes to dissolve the impurity metal in the tantalum powder, for example, reducing property. The metal and its oxide are then filtered to remove the spent acid solution, which is then dried and sieved.

The bulk density in the present invention is measured in accordance with GB/T 1479 "Determination of the bulk density of metal powders", Part 1, "Funnel method".

Gas and metal impurity content is measured in accordance with GB/T 15076 "Chemical Analysis Methods".

The particle size distribution and median particle size (D50) of the powders produced by the present invention were measured using a Malvern instrument Mastersizer 2000.

Surprisingly, it has been found that the high-temperature sintering described in the present invention brings many advantages: for example, 1). Since the raw material tantalum powder (sodium-reduced tantalum powder) is subjected to high-temperature heat treatment, fine particles are coagulated, adhered, grown, and tend to The homogenization reduces the activity of the powder and greatly reduces the risk of ignition during the subsequent mechanical crushing process. At the same time, due to the decrease in the activity of the powder, the possibility of re-agglomeration of the particles during the late crushing process is reduced, which is advantageous for fine grinding. 2). The degree of densification of the tantalum powder particles is increased by high-temperature sintering, which is beneficial to the control of the final oxygen content, and the corresponding bulk density is greatly increased. 3). By high-temperature sintering, the alkali metal such as K, Na, etc. brought in during the sodium reduction process escapes, and the purpose of purification is achieved. As is known to those skilled in the art, in semiconductor devices, alkali metals such as K, Na, etc. have a very bad influence on the interfacial properties of metal-oxide-semiconductor (MOS). 4) By high-temperature sintering, the gas impurities and moisture adsorbed on the surface of the tantalum powder can be removed, and the oxide film on the surface of the tantalum powder can be activated to increase the permeability of hydrogen gas, increase the hydrogenation effect, and avoid subsequent crushing due to incomplete hydrogenation. The large particles appearing in the process are not easily broken, resulting in a dispersion of the particle size distribution and a "tail". The presence of large particles causes uneven thickness of the deposited film and decreases reliability.

The bulk density as referred to herein refers to the mass of the metal powder that is freely filled per unit volume under the specific conditions of no vibration or no pressure.

In summary, the present invention has one or more of the following advantages:

The waste crucible powder produced in the production process of the capacitor with the high specific volume powder can be used as the raw material, the resource utilization is reasonable, the cost is low, and the adaptability to the raw material is strong;

Equipment investment is small;

high working efficiency;

Short process route; and

The process has a high safety factor.

detailed description:

The following examples are provided for purposes of illustration and not limitation. In order to highlight the advantageous effects of the present invention, the impurity content and bulk density in the raw material are measured, however, it is understood that a general sodium reduced niobium powder can serve as a raw material of the present invention.

Example 1: Raw material bismuth powder-1 as shown in Table 1 was used. The tantalum powder was heated to 1400 ° C under vacuum for 10 ^-3 Pa for 180 minutes, cooled, passivated, and baked to obtain a sintered mass. The agglomerate was heated to 800 ° C, cooled and subjected to hydrogenation treatment to obtain a crucible having good hydrogen embrittlement, and then the powder was crushed to obtain a crucible powder which was completely passed through a 100 mesh sieve. The above-mentioned glutinous powder is made of anhydrous ethanol as a ball milling medium, and methyl ethyl ketone is used as a grinding aid (the amount of methyl ketone added is 0.5% of the weight of cerium powder), and the mixed acid of HNO ₃ and HF is used after wet stirring ball milling for 0.5 hour. The metal impurities were removed by washing, and dried through a 200 mesh sieve to obtain a hydrogenated tantalum powder. Add 2% magnesium chips to the hydrogenated tantalum powder, heat it to 850 ° C for 2 hours in a closed oven under argon atmosphere, then vacuum again, and then heat-cool for 3 hours, then cool down and passivate. , dehydrogenation and oxygen reduction of bismuth powder. The tantalum powder with reduced oxygen concentration is dehydrogenated 10% by mass of HNO ₃ mixed with tantalum powder of the solid-liquid mass ratio of 1 HNO _3, stirred for 60min, tantalum powder was dissolved in magnesium and magnesium oxide, and then filtered The spent acid solution was removed, dried in a tray, and sieved to obtain a tantalum powder sample 1-1 of the present invention. The main impurity content, bulk density and size distribution are shown in Table 1.

Example 2: Raw material bismuth powder-1 as shown in Table 1 was still used. The tantalum powder was heated to 1600 ° C for 10 minutes under vacuum of 10 ^-3 Pa, cooled, passivated, and baked to obtain a sintered mass. The agglomerate was heated to 800 ° C, cooled and subjected to hydrogenation treatment to obtain a crucible having good hydrogen embrittlement, and then the powder was crushed to obtain a crucible powder which was completely passed through a 100 mesh sieve. The above-mentioned glutinous powder is made of anhydrous ethanol as a ball milling medium, and methyl ethyl ketone and isopropanol are used as grinding aids (the amount of methyl ethyl ketone added is 0.5% by weight of cerium powder, and the amount of isopropyl alcohol ketone added is 2.0 by weight of strontium powder). %), after performing wet agitating ball milling for 1.5 h, the metal impurities were removed by acid pickling with HNO ₃ and HF, and dried to a 200 mesh sieve to obtain a hydrogenated tantalum powder. Add 2% magnesium chips to the hydrogenated tantalum powder, heat it to 850 ° C for 2 hours in a closed oven, then vacuum, then heat for 3 hours and then cool down and passivate. A dehydrogenated and dehydrated niobium powder is obtained. The dehydrogenated and dehydrated niobium powder was mixed with 10% by mass of HNO ₃ , the solid-liquid ratio of niobium powder to HNO ₃ was 1:1, stirred for 60 min, the magnesium and magnesium oxide in the niobium powder were dissolved, and then the waste was removed by filtration. The acid solution was dried and sieved to obtain a powder sample 1-2 of the present invention. The main impurity content, bulk density and size distribution are shown in Table 1.

Comparative Example 1. Raw material bismuth powder-1 as shown in Table 1 was still used. The tantalum powder was directly subjected to wet agitating ball milling without heat treatment for 1.5 hours, and then washed with a mixed acid of HNO ₃ and HF to remove metal impurities, and dried through a 200 mesh sieve to obtain a hydrogenated tantalum powder. Add 2% magnesium chips to the hydrogenated tantalum powder, heat it to 850 ° C for 3 hours in a closed oven, then vacuum, and then heat for 3 hours, then cool down and passivate. A non-hydrogen-containing tantalum powder is obtained. The dehydrogenated and dehydrated niobium powder was mixed with 10% by mass of HNO ₃ , the solid-liquid ratio of niobium powder to HNO ₃ was 1:1, stirred for 60 min, the magnesium and magnesium oxide in the niobium powder were dissolved, and then the waste was removed by filtration. The acid solution was dried and sieved to obtain a comparative powder sample 1-1. The main impurity content, bulk density and size distribution are shown in Table 1.

Example 3: Raw material tantalum powder-2 as described in Table 1 was used as a raw material. The tantalum powder was heated to 1800 ° C under vacuum for 10 ^-3 Pa for 120 minutes, cooled, passivated, and baked to obtain a sintered mass. The agglomerate was heated to 800 ° C, cooled and subjected to hydrogenation treatment to obtain a crucible having good hydrogen embrittlement, and then the powder was crushed to obtain a crucible powder which was completely passed through a 100 mesh sieve. The above-mentioned glutinous rice powder is made of anhydrous ethanol as a ball milling medium, and methyl ethyl ketone and isopropyl alcohol are used as grinding aids (the amount of methyl ethyl ketone added is 1.0% by weight of cerium powder, and the amount of isopropyl alcohol ketone added is 3.0 by weight of strontium powder). %), after performing wet agitating ball milling for 1.5 h, the metal impurities were removed by acid pickling with HNO ₃ and HF, and dried to a 200 mesh sieve to obtain a hydrogenated tantalum powder. Add 2% magnesium chips to the hydrogenated tantalum powder, heat it to 830 ° C for 2 hours in a closed oven, then vacuum, and then heat for 3 hours, then cool down and passivate. The bismuth powder after dehydrogenation and oxygen reduction is obtained. The dehydrogenated and dehydrated niobium powder was mixed with 10% by mass of HNO ₃ , the solid-liquid ratio of niobium powder to HNO ₃ was 1:1, stirred for 60 min, the magnesium and magnesium oxide in the niobium powder were dissolved, and then the waste was removed by filtration. The acid solution was again dried in a tray and sieved to obtain a tantalum powder sample 2-1 of the present invention. The main impurity content, bulk density and size distribution are shown in Table 1.

Comparative Example 2: Raw material tantalum powder-2 as described in Table 1 was still used as a raw material. The tantalum powder is directly heated to 800 ° C without heat treatment, and then subjected to hydrogenation treatment to obtain a hydrogenated tantalum powder, which is then ball milled by wet stirring for 1.5 hours, and then washed with a mixed acid of HNO ₃ and HF to remove metal impurities and dried. A 200 mesh sieve gave a hydrogenated tantalum powder. Add 2% magnesium chips to the hydrogenated tantalum powder, heat it to 830 ° C for 2 hours in a closed oven, then vacuum, and then heat for 3 hours, then cool down and passivate. A dehydrogenated and oxygen-reducing tantalum powder is obtained. The dehydrogenated and dehydrated niobium powder was mixed with 10% by mass of HNO ₃ , the solid-liquid ratio of niobium powder to HNO ₃ was 1:1, stirred for 60 min, the magnesium and magnesium oxide in the niobium powder were dissolved, and then the waste was removed by filtration. The acid solution was dried and sieved to obtain a bismuth powder comparative sample 2-1 of the present invention. The main impurity content, bulk density and size distribution are shown in Table 1.

Example 4: The raw material tantalum powder-2 as described in Table 1 was still used as a raw material. The tantalum powder was heated to 1950 ° C for 120 minutes under vacuum of 10 ^-3 Pa, cooled, passivated, and baked to obtain a sintered cake. The agglomerate was heated to 800 ° C, cooled and subjected to hydrogenation treatment to obtain a crucible having good hydrogen embrittlement, and then the powder was crushed to obtain a crucible powder which was completely passed through a 100 mesh sieve. The above-mentioned glutinous powder was prepared by using anhydrous ethanol as a ball milling medium and isopropanol as a grinding aid (the amount of isopropanol ketone added was 5.0% by weight of the cerium powder), and mixing with HNO ₃ and HF after wet stirring ball milling for 3 hours. The acid pickling removes the metal impurities and is dried over a 200 mesh sieve to obtain a hydrogenated tantalum powder. Add 2% magnesium chips to the hydrogenated tantalum powder, heat it to 830 ° C for 2 hours in a closed oven, then vacuum, and then heat for 3 hours, then cool down and passivate. A dehydrogenated and oxygen-reducing tantalum powder is obtained. The dehydrogenated and dehydrated niobium powder was mixed with 10% by mass of HNO ₃ , the solid-liquid ratio of niobium powder to HNO ₃ was 1:1, stirred for 60 min, the magnesium and magnesium oxide in the niobium powder were dissolved, and then the waste was removed by filtration. The acid solution was dried in a tray and sieved to obtain a tantalum powder sample 2-2 of the present invention. The main impurity content, bulk density and size distribution are shown in Table 1.

Comparative Example 3: The raw material tantalum powder-2 as described in Table 1 was still used as a raw material. The tantalum powder is directly heated to 800 ° C without heat treatment, and then subjected to hydrogenation treatment to obtain a hydrogenated tantalum powder, which is then ball milled by wet stirring for 3 hours, and then washed with a mixed acid of HNO ₃ and HF to remove metal impurities, and dried and discharged. There was a fire and the material was not processed. For convenience of comparison, it is still indicated by the comparison sample 2-2 in the table.

Example 5: Raw material tantalum powder-3 as described in Table 1 was used as a raw material. The tantalum powder was heated to 1500 ° C under vacuum for 10 ^-3 Pa for 180 minutes, cooled, passivated, and baked to obtain a sintered mass. The agglomerate was heated to 800 ° C, cooled and subjected to hydrogenation treatment to obtain a crucible having good hydrogen embrittlement, and then the powder was crushed to obtain a crucible powder which was completely passed through a 100 mesh sieve. The above-mentioned glutinous powder is made of anhydrous ethanol as a ball milling medium, butanone is used as a grinding aid (the amount of methyl ethyl ketone added is 1.5% of the weight of cerium powder), and the mixed acid of HNO ₃ and HF is used after wet stirring ball milling for 2.0 hours. The metal impurities were removed by washing, and dried through a 200 mesh sieve to obtain a hydrogenated tantalum powder. Add 2% magnesium chips to the hydrogenated tantalum powder, heat it to 850 ° C for 2 hours in a closed oven, then vacuum, and then heat for 3 hours, then cool down and passivate. The bismuth powder after dehydrogenation and oxygen reduction is obtained. The dehydrogenated and dehydrated niobium powder was mixed with 10% by mass of HNO ₃ , the solid-liquid ratio of niobium powder to HNO ₃ was 1:1, stirred for 60 min, the magnesium and magnesium oxide in the niobium powder were dissolved, and then the waste was removed by filtration. The acid solution was again dried in a tray and sieved to obtain a tantalum powder sample 3-1 of the present invention. The main impurity content, bulk density and size distribution are shown in Table 1.

Comparative Example 4: The raw material 钽 powder-3 in Table 1 was still used as a raw material. The tantalum powder was directly subjected to wet stirring ball milling for 2.0 hours without heat treatment, and then the metal impurities were removed by acid pickling with HNO3 and HF, and dried to a 200 mesh sieve to obtain a hydrogenated tantalum powder. Add 2% magnesium chips to the hydrogenated tantalum powder, heat it to 850 ° C for 3 hours in a closed oven, then vacuum, and then heat for 3 hours, then cool down and passivate. A dehydrogenated and oxygen-reducing tantalum powder is obtained. The dehydrogenated and dehydrated niobium powder was mixed with 10% by mass of HNO ₃ , the solid-liquid ratio of niobium powder to HNO ₃ was 1:1, stirred for 60 min, the magnesium and magnesium oxide in the niobium powder were dissolved, and then the waste was removed by filtration. The acid solution was dried and sieved to obtain a comparative bismuth powder comparison sample 3-1. The main impurity content, bulk density and size distribution are shown in Table 1.

Note that the D50 of Comparative Example 2-1 was 4.967 μm, but its bulk density was 1.22, and thus was not within the scope of the present invention.

It can be seen from the above data that the cerium powder treated by the method of the present invention has a concentrated particle size distribution range and a small size, D50 < 5 μm, and has a low O, K, Na impurity content and a large bulk density.

The analysis equipment and model of each parameter involved in this application are shown in the following table.

Analysis Project Analyze device name Specification model Average particle size (μm) Malvern laser particle size analyzer Mastersizer 2000 O Oxygen and nitrogen analyzer LECO CS-436 K, Na Atomic absorption spectrometer Varian 220FS/220Z Fe, Ni, Cr Direct Reading Spectrometer GV-5 Bulk Density Scott Cup ——

Claims (10)

A fine tantalum powder having a D50 < 5 μm, preferably D50 < 4.5 μm, characterized by a bulk density of 2.0-6.0 g/cm ³ , preferably 2.2-4.5 g/cm ³ . The fine tantalum powder according to claim 1, wherein the niobium powder has a K+Na content of not more than 20 ppm, preferably not more than 15 ppm; and optionally an oxygen content of not more than 6000 ppm, preferably not more than 4000 ppm. A method of preparing the fine tantalum powder according to claim 1 or 2, the method comprising: 1) providing powdered raw materials; 2) sintering the raw material at a high temperature to obtain a sintered block; 3) hydrocracking the agglomerate to obtain hydrogenated tantalum powder, and 4) Dehydrogenation, dehydration, pickling, drying and sieving of the hydrogenated tantalum powder. The method of claim 3 wherein the hydrogenated powder is mechanically broken up in a hydrocracking process to pass through a 100 mesh screen and then ground using a wet agitating ball mill until its D50 &lt; 5 μm, followed by pickling. The method of claim 4 wherein a surfactant such as methyl ethyl ketone and/or isopropanol is added to the milling media used in the ball milling process, preferably in an amount of from 0.5 to 5% by weight based on the weight of the tantalum powder. The method of any one of claims 3 to 5, wherein the high temperature sintering is carried out under high vacuum conditions, for example, from 1 ^{-2 to} 10 ^-5 Pa, preferably from about 10 ^-3 pa. The method according to any one of claims 3 to 5, wherein the powdered raw material is sodium reduced niobium powder, for example, waste tantalum powder produced in the production process of tantalum powder, particularly in the production process of high specific volume tantalum powder for capacitors. The waste powder is used as a raw material. The method according to any one of claims 3 to 7, wherein the sintering temperature for the high-temperature sintering is 1400 to 2000 ° C, and the holding time at the sintering temperature is 1-5 hours, preferably 2-3 hours. The method according to claim 4 or 5, wherein the zirconia balls (for example, zirconia balls having a diameter of from 1 to 5 mm, preferably from 2 to 4 mm) are used as a ball milling medium, preferably water or an organic solvent, preferably alcohol, as a dispersion medium, and continuously ball milled at 0.5. -4h, preferably 1-3h, such that D50 < 5 μm. Use of the tantalum powder of claims 1-2 for semiconductor and/or surface coating.