Molybdenum powder

Abstract

This powder containing molybdenum has the average particle diameter of 0.5-3.0 μm by a Fsss method, the BET specific surface area of 0.3 m2 / g to 5.5 m2 / g by a gas absorption method, the aggregation coefficient of 5.5 or lower as calculated from the average particle diameter by the Fsss method and the BET specific surface area by the gas absorption method, and the apparent density of 2.13 g / cm3 or lower as measured in accordance with JIS Z 2504 (2012).

Description

Technical Field

[0001] The present disclosure relates to a powder containing molybdenum. This application claims priority based on Japanese Patent Application No. 2021-168283, filed on October 13, 2021. All the descriptions described in the Japanese patent application are incorporated herein by reference.

Background Art

[0002] Conventionally, a powder containing molybdenum has been disclosed, for example, in Japanese Patent Application Laid-Open No. 11-36006 (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The powder containing molybdenum of the present disclosure has an average particle size by the Fsss method of 0.5 μm or more and 3.0 μm or less, a BET specific surface area by the gas absorption method of 0.3 m 2 / g or more and 5.5 m 2 / g or less, an aggregation coefficient calculated from the average particle size by the Fsss method and the BET specific surface area of 5.5 or less, and an apparent density measured according to JIS Z2504 (2012) of 2.13 g / cm 3 or less.

Modes for Carrying Out the Invention

[0005] [Problems to be Solved by the Present Disclosure] Conventional powders containing molybdenum had a problem of poor sinterability.

[0006] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0007] In the conventional method, ammonium molybdate or MoO 3 (molybdenum trioxide) powder is used to fill a reduction boat (such as a heat-resistant alloy boat), inserted into a reduction furnace in a hydrogen atmosphere, and reduced at a constant temperature to produce an intermediate product. The intermediate product is further heated at a high temperature to produce Mo powder. As a characteristic of the molybdenum powder produced by this method, a sintering temperature of about 1800°C to 2000°C is required to obtain a dense molybdenum sintered body by a general powder metallurgy method, and sintering treatment at a high temperature is essential. For this reason, the sintering cost of the powder containing molybdenum produced by the conventional method becomes high.

[0008] In addition, in the joining with substances other than molybdenum such as ceramics in metallization, etc., generally, the sintering (joining) temperature with the material containing molybdenum powder is as high as 1000°C or more, and problems such as warping of the workpiece after firing may occur due to the difference in thermal expansion with substances such as ceramics other than molybdenum. The cause is considered to be a problem with the shrinkage characteristics during sintering caused by variations in the particle size of the molybdenum powder and aggregation of the particles.

[0009] In the case of the method for producing powder containing molybdenum in the conventional powder metallurgy method, aggregation is likely to occur. In order to obtain relatively sinterable fine molybdenum powder by the conventional method, it is necessary to reduce at a relatively low temperature, and as a result, grain growth does not proceed sufficiently, and there is a tendency for particularly more aggregation. There is a trade-off relationship between reducing the particle size for the purpose of improving sinterability and the large amount of aggregation of the fine molybdenum powder produced for this purpose.

[0010] Considering these, molybdenum powder with fine particles, less aggregation, and good sinterability at low temperature is considered useful.

[0011] In the powder metallurgy method of Patent Document 1, ammonium molybdate or MoO 3When reducing the powder of molybdenum trioxide, K and P are doped into the intermediate product generated, and reduction is carried out in a hydrogen atmosphere. A method for producing molybdenum powder with a bulk density of 2.2 or more and no particles of 22 μm or less in the particle size distribution is described. The Mo powder obtained by the method of Patent Document 1 has less aggregation than conventional powders containing molybdenum, but it is considered that its sinterability is not good because of its large particle size. Further, Patent Document 1 describes an improvement in the packing density of Mo powder, but does not mention sinterability at all.

[0012] The powder containing molybdenum of the present disclosure has an average particle size (hereinafter, also referred to as Fsss average particle size) by the Fsss method of 0.5 μm or more and 3.0 μm or less, and a BET specific surface area (hereinafter, also referred to as BET specific surface area) by the gas absorption method of 0.3 m 2 / g or more and 5.5 m 2 / g or less, and an aggregation coefficient calculated from the average particle size by the Fsss method and the BET specific surface area is 5.5 or less.

[0013] (1) Description of the product The present disclosure relates to a powder containing molybdenum with less aggregation and excellent sinterability, and it has been found that an effect can be obtained by setting the following characteristic values within a predetermined range.

[0014] Regarding the Fsss average particle size, BET specific surface area, and aggregation coefficient, the required ranges are: Fsss average particle size of 0.5 μm or more and 3.0 μm or less, BET specific surface area of 0.3 m 2 / g or more and 5.5 m 2 / g or less, and aggregation coefficient of 5.5 or less. The aggregation coefficient γ is represented by the following formula.

[0015] γ = Fsss average particle size / d = (Fsss average particle size × BET specific surface area × ρ) / 6 Here, d is the BET particle size calculated from the BET specific surface area, and ρ is the density.

[0016] A more preferable range is: Fsss average particle size of 0.5 μm or more and 3.0 μm or less, BET specific surface area of 0.3 m 2 / g or more and 5.5 m 2Below / g, the agglomeration coefficient is 1.5 or more and 5.1 or less.

[0017] A more preferable range is that the Fsss average particle size is 0.5 μm or more and 2.5 μm or less, and the BET specific surface area is 0.4 m 2 / g or more and 5.5 m 2 / g or less, and the agglomeration coefficient is 1.5 or more and 5.1 or less. If it is within this range, the sinterability is further improved.

[0018] The preferable range of molybdenum purity is 99.5 mass% or more. A more preferable range is that the molybdenum purity is 99.9 mass% or more. If it is within this range, the risk of impurities affecting the sinterability is small.

[0019] As a composition other than molybdenum, it can contain at least one of Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, Si, Na, K, As, P, and W. The proportion of each composition is less than 0.1 mass%. For the analysis method, Fe, Ca, Si, Al, and Mg are determined by JISH1404 (2001), K, Na, and As are determined by atomic absorption spectrometry (manufactured by Analytik Jena Japan: contrAA300), and P and other metals can be determined by ICP emission spectrometry (manufactured by Shimadzu Corporation: ICPS - 8100).

[0020] The preferable range of the particle size distribution is that D90 / D10 is 4.3 or less. A more preferable range is that D90 / D10 is 1.5 or more and 4.0 or less. If it is within this range, the sinterability is further improved.

[0021] D90 represents the D90% diameter, which means the particle size at which the cumulative frequency of particles with a particle size below this value is 90% in the particle size distribution graph. D10 represents the D10% diameter, which means the particle size at which the cumulative frequency of particles with a particle size below this value is 10% in the particle size distribution graph. If it is within this range, the sinterability is further improved.

[0022] The preferable range of the crystallite size is 1000 nm or less. A more preferable range is that the crystallite size is 75 nm or more and 980 nm or less. If it is within this range, the sinterability is further improved.

[0023] The preferable range of lattice distortion is 0.018% or more. A more preferable range is that the lattice distortion is 0.02% or more. If it is within this range, the sinterability is further improved.

[0024] As these effects, a relative density of 70% or more can be achieved during sintering at 800 °C, and a relative density of 85% or more can be achieved during sintering at 1400 °C.

[0025] The apparent density measured according to JIS Z2504 (2012) is 2.13 g / cm 3 or less. Preferably, the tap density measured according to JIS Z2512 (2012) is 4.34 g / cm 3 or less.

[0026] (2) Manufacturing method Powder containing molybdenum is manufactured according to Step 1 (raw material sieving), Step 2 (primary reduction), Step 3 (intermediate sieving), Step 4 (secondary reduction), Step 5 (final sieving), and Step 6 (mortar pulverization).

[0027] Step 1: Raw material sieving The raw material MoO 3 powder is sieved. The raw material is passed through a sieve mesh with a predetermined mesh size to remove coarse grains and agglomerated powder, and the undersize is recovered. The mesh size of the sieve is appropriately changed according to the raw material and the target molybdenum powder particle size.

[0028] Step 2: Primary reduction (MoO 3 →MoO 2 ) The MoO 3 sieved in Step 1 is filled into a heat-resistant alloy boat, and is reduced to MoO 3 →MoO 2 and taken out. Optimal reduction conditions (temperature, hydrogen flow rate, boat filling amount, equipment used, etc.) are appropriately selected according to the target powder particle size.

[0029] Step 3: Intermediate sieving The MoO 2 powder obtained in Step 2 is sieved. The MoO 2Pass the powder through to remove coarse particles and agglomerated powder and recover the undersize. The mesh opening of the sieve is appropriately changed according to the MoO 2 powder and the target molybdenum powder particle size.

[0030] Step 4: Two-stage reduction (MoO 2 →Mo) Fill the MoO 2 screened in Step 3 into a heat-resistant alloy boat, reduce it to MoO 2 →Mo and take it out. Appropriate selection of the optimal reduction conditions (temperature, hydrogen flow rate, boat filling amount, equipment used, etc.) according to the target powder particle size. Thereby, a powder containing molybdenum is obtained.

[0031] Step 5: Final screening Screen the powder containing molybdenum obtained in Step 4. Pass the powder containing molybdenum through a sieve with a predetermined mesh opening to remove coarse particles and agglomerated powder and recover the undersize. The mesh opening of the sieve is appropriately changed according to the powder containing molybdenum and the target molybdenum powder particle size.

[0032] Step 6: Mortar grinding Rub the powder containing molybdenum obtained in Step 5 in a mortar. Thereby, the crushing of the slightly remaining agglomerated powder proceeds and lattice strain is introduced.

[0033] [Details of Embodiments of the Present Disclosure] <Example> Manufacture of Sample No. 1 A powder containing molybdenum was manufactured according to Step 1 (raw material screening), Step 2 (one-stage reduction), Step 3 (intermediate screening), Step 4 (two-stage reduction), Step 5 (final screening), and Step 6 (mortar grinding).

[0034] Step 1: Raw material screening Use raw materials with an Fsss average particle size of 4 μm and MoO 3 with a molybdenum purity of 66.33% or more (99.5% or more in terms of Mo powder) in MoO 3 powder. Screen with a mesh opening of 250 μm to remove coarse particles and agglomerated powder and recover the undersize.

[0035] The Fsss average particle size is preferably 0.5 μm or more and 50 μm or less. If it exceeds this range, the Fsss average particle size of the powder containing molybdenum may be 3.0 μm or more. Note that "may be" indicates that there is a slight possibility of it being so, and does not mean that it will be so with a high probability.

[0036] MoO 3 The molybdenum purity in it is preferably 66.33% or more (99.5% or more in terms of Mo powder).

[0037] If it is less than this, it will be of low purity and may not be suitable for industrial products. Note that more preferably, the molybdenum purity in MoO 3 is more preferably 66.6% or more (99.9% or more in terms of Mo powder). This is because the more impurities contained in molybdenum, the more likely it is to affect the sinterability of molybdenum.

[0038] The mesh opening is preferably 300 μm or less. If it exceeds this, there is a possibility that coarse particles or agglomerated powder cannot be removed.

[0039] Step 2: One-stage reduction (MoO 3 →MoO 2 ) The MoO 3 screened in Step 1 is filled into a heat-resistant alloy boat to a thickness of 35 mm. Using a pusher-type reduction furnace, reduction treatment is carried out under the conditions of a hydrogen flow rate of 5 m 3 / h and a reduction temperature of 500 °C to obtain MoO 2 .

[0040] The thickness of the MoO 3 filled in the alloy boat is preferably 50 mm or less. If it exceeds this, there is a possibility that the reduction of MoO 3 in the boat will not proceed.

[0041] The hydrogen flow rate is preferably 3 m 3 / h or more. If it is less than this, there is a possibility that the reduction of MoO 3 in the boat will not proceed.

[0042] The reduction temperature is preferably 450 °C or higher and 650 °C or lower. If it exceeds this range, since it will be near the melting point, there is a risk that the raw material will melt. If it is less than this, there is a risk that the reduction of MoO in the boat will not proceed. 3 in the boat may not proceed. 3

[0043] Step 3: Intermediate screening The MoO obtained in Step 2 2 is screened with a mesh opening of 75 μm to remove coarse grains and agglomerated powder, and the undersize is collected.

[0044] The mesh opening is preferably 150 μm or less. If it exceeds this, there is a risk that coarse grains or agglomerated powder cannot be removed.

[0045] Step 4 Two-stage reduction (reduction of MoO 2 ) After the intermediate screening in Step 3, MoO 2 is filled into a heat-resistant alloy boat to a thickness of 20 mm. Using a pusher-type reduction furnace, reduction treatment is carried out under conditions of a hydrogen flow rate of 10 m 3 / h and a reduction temperature in the range of about 600 - 920 °C to obtain a powder containing molybdenum.

[0046] The thickness of MoO filled in the heat-resistant alloy boat 2 is preferably 50 mm or less. If it exceeds this, there is a risk that the reduction of MoO 2 in the boat may not proceed.

[0047] The hydrogen flow rate is preferably 5 m 3 / h or more. If it is less than this, there is a risk that the reduction of MoO 2 in the boat may not proceed.

[0048] The reduction temperature is preferably 600 °C or higher and 950 °C or lower. If it exceeds this, the Fsss average particle size of the powder containing molybdenum may become 3.0 μm or more. If it is less than this, there is a risk that the reduction of MoO 2 in the boat may not proceed.

[0049] Step 5 Final screening The obtained molybdenum-containing powder is sieved with a mesh size of 45 μm or less (20 μm for Sample No. 1), and the coarse particles and agglomerated powder are removed, and the undersize is recovered.

[0050] The mesh size is preferably 45 μm or less. If it exceeds this, there is a risk that coarse particles or agglomerated powder cannot be removed.

[0051] Step 6 Mortar grinding The Mo powder obtained by the final sieving is ground in an automatic mortar. 500 g is charged per batch and it is carried out for 10 minutes.

[0052] For Sample Nos. 2 to 33, based on the production method of Sample No. 1, the reduction conditions (temperature, hydrogen flow rate, boat filling amount) in the two-stage reduction in Step 4 and the mesh size of the sieve in Step 5 final sieving were changed.

[0053] For Sample Nos. 41 to 60 as comparative examples, the reduction conditions (temperature, hydrogen flow rate, boat filling amount) in the two-stage reduction in Step 4 and the mesh size of the sieve in Step 5 final sieving were changed, and Step 6 mortar grinding was omitted. Thereby, powders containing molybdenum of Sample Nos. 1 to 33 and 41 to 60 were obtained.

[0054] The powders containing molybdenum were evaluated as follows. <Measurement method of Fsss average particle size> The measurement of the Fsss average particle size is carried out by the Fisher method.

[0055] The apparatus used is Fisher Sub-Sieve Sizer Model95 from Fisher Scientific. The sample tube is filled with a sample of true density, the porosity is determined from the sample height, air at a pressure of 1 MPa is passed through it, the manometer water level is read as a value on the calculator chart, and that value is taken as the Fsss average particle size and the unit is expressed in μm. The Fsss average particle size represents the average particle size of the powder, and the lower the numerical value, the smaller the average particle size.

[0056] <BET specific surface area> The BET specific surface area is measured by the gas adsorption method. The measuring device used is the Macsorb HM Model-1208 manufactured by MOUNTECH Co., Ltd. Nitrogen gas is adsorbed onto the powder, and the BET specific surface area of the powder is measured from the amount of adsorbed gas molecules. The unit of the BET specific surface area is m 2 / g, and the smaller the Fsss average particle size, the greater the tendency for the BET specific surface area to be larger.

[0057] <Coefficient of aggregation> The coefficient of aggregation is expressed as the ratio of the Fsss average particle size (μm) to the BET particle size (μm) obtained from the BET specific surface area. The closer the coefficient of aggregation is to 1, the less the aggregation, and the larger it is, the more the aggregation. In principle, the coefficient of aggregation takes a value of ≧1.

[0058] The Fsss average particle size means the secondary particle size including aggregation, while the BET particle size obtained from the BET specific surface area means a value close to the primary particle size without aggregation.

[0059] When assuming that the particles are spherical, the following equation holds between the BET specific surface area (m 3 / g) and the BET particle size (diameter) d (μm). Here, ρ represents the density (g / cm 3 ).

[0060] BET specific surface area = 6 / ρd That is, the BET particle size d is d = 6 / (ρ × BET specific surface area).

[0061] Therefore, the coefficient of aggregation γ is γ = Fsss average particle size / d = (Fsss average particle size × BET specific surface area × ρ) / 6.

[0062] <Method for measuring particle size distribution> The particle size distribution is measured by the laser diffraction / scattering method. By this method, D90 and D10 are obtained.

[0063] The measuring device used is the Microtrac BEL MT3300EX2, which is a laser light diffraction / scattering type. Pure water is used as the solvent, and the particle refractive index is 2.76 and the solvent refractive index is 1.33.

[0064] The larger the value of D90 / D10, the broader the particle size distribution, and the smaller the value, the sharper (more uniform) the particle size distribution.

[0065] <Lattice strain, crystallite size> Lattice strain and crystallite size are measured by X-ray diffraction method.

[0066] The device used is EMPYREAM from PANalytical. When X-rays of a certain wavelength irradiate the analysis sample, the scattered X-rays show a diffraction pattern specific to the substance depending on the arrangement state of the atoms and molecules of the substance. Rietveld analysis is performed by fitting this diffraction pattern with a non-linear least squares method to obtain the lattice strain and crystallite size.

[0067] The crystallite size indicates the smallest unit part that can be regarded as a single crystal within the crystallite grains. When the crystallite size is small, the particle diameter tends to be small. When the particle diameter is small, the contact area between particles becomes large and sintering progresses easily, so the relative density of the sintered body can be improved.

[0068] Looking at the substance at the atomic level, the atoms are arranged in a lattice. When a force is applied to this lattice, the shape of the lattice changes and strain occurs. This strain is called lattice strain. <Apparent density, tap density> The analysis method for apparent density is JIS Z2504 (2012), and the analysis method for tap density is JIS Z2512 (2012). Comparing the measurement method of the Tungsten - Molybdenum Industry Association Standard TMS1101, which is the measurement method in Patent Document 1, with the above JIS measurement method, the measurement results are almost the same.

[0069] These results are shown in Table 1 and Table 2.

[0070]

Table 1

[0071]

Table 2

[0072] In Tables 1 and 2, “final screening mesh size” refers to the mesh size of the sieve used in the final screening in Step 5. “Mortar grinding” indicates the presence or absence of mortar grinding in Step 6. “Fsss”, “BET”, “aggregation coefficient”, “particle size distribution”, and “crystallite size” refer to the Fsss average particle size, BET specific surface area, aggregation coefficient, particle size distribution D90 / D10, and crystallite size of the molybdenum-containing powder obtained through Step 5 or 6.

[0073] Using the molybdenum-containing powder shown in Tables 1 and 2, a sintered body was fabricated and its density was determined. The method for measuring the density of the sintered body is as follows.

[0074] For the production of the sintered body for density measurement, first, 10 g of the molybdenum-containing powder was put into a mold with a diameter of φ20 mm and press-molded with a 30 t press machine so that a pressure of 50 MPa was applied. Next, sintering was performed for 2 hours in a hydrogen atmosphere at a sintering temperature of 800 °C or for 2 hours at a sintering temperature of 1400 °C to obtain a sintered body. After infiltrating paraffin into the sintered body for about 10 minutes to fill the voids in the sintered body, the density of the sintered body was measured using the Archimedes method.

[0075] These results are shown in Tables 3 and 4.

[0076]

Table 3

[0077]

Table 4

[0078] In Tables 3 and 4, “relative density after sintering at 800 °C” refers to the relative density of the sintered body after sintering at a temperature of 800 °C. “Relative density after sintering at 1400 °C” refers to the relative density of the sintered body after sintering at a temperature of 1400 °C.

[0079] When sintered at a sintering temperature of 800 °C, if the relative density is 70% or more, it was judged that the sinterability was good. When sintered at a sintering temperature of 1400 °C, if the relative density is 85% or more, it was judged that the sinterability was good.

[0080] It was found that Samples Nos. 1 to 33 contain molybdenum powder that has less aggregation, is fine-grained and uniform-grained, and has a large lattice strain, so it is easier to sinter at a lower temperature than before. As a result, the sintering cost is reduced and the energy used is also reduced, which solves the energy problem.

[0081] Since it can be sintered at a low temperature, the thermal expansion difference from other substances is small and it is easy to sinter. Therefore, when used for metallizing applications, etc., the shrinkage rate can be controlled by the sintering temperature.

[0082] For sintered bodies that can be plastically processed such as rolling and forging, a relative density of 85% or more is required. To manufacture it, it was necessary to sinter the molybdenum compact at 1800 °C or higher. However, since the product of the present disclosure can be manufactured at a temperature of 1400 °C, the manufacturing cost can be reduced.

[0083] For Sample Nos. 4, 10, 18, and 28 whose aggregation coefficient exceeds 5.1, it can be seen that the sinterability is slightly reduced compared to the samples in Tables 1 and 3 having the same Fsss average particle size or BET specific surface area. Therefore, the aggregation coefficient is more preferably 1.5 or more and 5.1 or less.

[0084] Also, from the results of Tables 1 and 3, the smaller the Fsss average particle size, the higher the relative density after sintering at 800 °C and the relative density after sintering at 1400 °C tend to be, and the BET specific surface area tends to be larger.

[0085] For sample numbers 28, 29, 30, 31, 32, and 33 where the Fsss average particle size exceeds 2.5 μm, the relative density after sintering at 800 °C and the relative density after sintering at 1400 °C become values close to the lower limits of 70% or more and 85% or more, which were judged to be effective in this disclosure. Furthermore, for sample numbers 30 and 33 where the Fsss average particle size is 2.5 μm and the BET specific surface area is less than 0.5, it can be seen that the sinterability decreases, with the relative density after sintering at 800 °C being 72% or less and the relative density after sintering at 1400 °C being 85% or less compared to sample numbers 27 and 29, respectively. Therefore, it is more preferable that the Fsss average particle size is 0.5 μm or more and 2.5 μm or less, the BET specific surface area is 0.4 m 2 / g or more and 5.5 m 2 / g or less, and the aggregation coefficient is 1.5 or more and 5.1 or less.

[0086] For sample numbers 8, 18, and 28 where the particle size distribution D90 / D10 exceeds 4.3, it can be seen that the sinterability is slightly reduced compared to the samples in Tables 1 and 3 having the same Fsss average particle size or BET specific surface area. Therefore, it is preferable that the particle size distribution D90 / D10 is 4.3 or less.

[0087] Furthermore, for sample numbers 11, 17, 19, and 24 where the particle size distribution D90 / D10 exceeds 4.0, it can be seen that the sinterability is slightly reduced compared to the samples in Tables 1 and 3 having the same Fsss average particle size or BET specific surface area. Therefore, it is more preferable that the particle size distribution D90 / D10 is 4.3 or less.

[0088] For sample numbers 31 and 32 where the crystallite size exceeds 1000 nm, it can be seen that the sinterability is slightly reduced compared to the samples in Tables 1 and 3 having the same Fsss average particle size or BET specific surface area. Therefore, it is preferable that the crystallite size is 1000 nm or less.

[0089] Furthermore, it can be seen that sample number 33 with a crystallite size exceeding 980 nm has a slightly lower sinterability compared to the samples in Tables 1 and 3 having an equivalent Fsss average particle size or BET specific surface area. Therefore, the crystallite size is more preferably 75 nm or more and 980 nm or less.

[0090] Furthermore, it can be seen that sample numbers 11, 17, 22, 24, and 32 with a lattice strain of less than 0.018% have a slightly lower sinterability compared to the samples in Tables 1 and 3 having an equivalent Fsss average particle size or BET specific surface area. Therefore, the lattice strain is preferably 0.018% or more.

[0091] Furthermore, it can be seen that sample numbers 18, 28, and 31 with a lattice strain of less than 0.020% have a slightly lower sinterability compared to the samples in Tables 1 and 3 having an equivalent Fsss average particle size or BET specific surface area. Therefore, the lattice strain is more preferably 0.020% or more.

[0092] From Tables 1 and 2, the apparent density measured according to JIS Z2504 (2012) is less than 1.96 g / cm 3 The tap density measured according to JIS Z2512 (2012) is preferably 4.34 g / cm 3 or less.

[0093] The embodiments and examples disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims rather than the above description, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

Claims

Claim 1 The average particle size by the Fsss method is 0.5 μm or more and 3.0 μm or less, the BET specific surface area by the gas absorption method is 0.3 m ２ / g or more and 5.5 m ２ / g or less, the aggregation coefficient calculated from the average particle size by the Fsss method and the BET specific surface area by the gas adsorption method is 5.5 or less, and the apparent density measured according to JIS Z2504 (2012) is 2.13 g / cm ３ or less, A molybdenum powder having a ratio D90 / D10 of 4.3 or less when the D10% diameter and D90% diameter of the particle size distribution are D10 and D90, respectively, and a molybdenum purity of 99.5 mass% or more. Claim 2 The molybdenum powder according to claim 1, having a crystallite size of 1000 nm or less. Claim 3 The molybdenum powder according to claim 1 or 2, having a lattice strain of 0.018% or more. Claim 4 The tap density measured in accordance with JIS Z 2512 (2012) is 4.34 g / cm ３ The molybdenum powder according to claim 1 or 2, which is as follows.

Images