Process For Preparing Tantalum Powders For Use In An Electrolytic Capacitor With High Reliability and High Specific Capacitance

Abstract

The present invention provides a process for preparing tantalum powders for use in an electrolytic capacitor with high reliability and high specific capacitance, characterized in that the ratio of the average particle size of raw tantalum powders to the average particle size of tantalum flake powders is 0.5-25, preferably 1.5-10, more preferably 2-5. The process of the present invention is simple and has good controllability, the tantalum flake powder obtained has low content of metal impurities, high specific surface area, and after agglomerated, have good flowability and moldability, have high specific capacitance, and when used under high voltage, have low leakage current and high breakdown voltage.

Claims

1. A process for preparing tantalum powders for use in an electrolytic capacitor with high reliability and high specific capacitance, wherein the ratio of the average particle size of raw tantalum powders to the average particle size of tantalum flake powders is 0.5-25.

2. A process for preparing tantalum powders for use in an electrolytic capacitor with high reliability and high specific capacitance, comprising the steps of: 1) preparation of raw tantalum powders: providing raw tantalum powders having suitable average particle size according to the requirement for targeted average particle size of tantalum flake powders, wherein the ratio of the average particle size of raw tantalum powders to the average particle size of tantalum flake powders is 0.5-25; 2) preparation of tantalum flake powders: processing the raw tantalum powders into flaky shape to obtain tantalum flake powders with a processing method comprising: ball milling, pounding or squashing; 3) removal of impurities by acid washing: acid washing the tantalum flake powders obtained in step 2) to decrease the impurities therein to obtain flake raw powders; 4) subsequent processing step of flake raw powders: subjecting the flake raw powders obtained in step 3) to subsequent processing step to give tantalum powders for use in an electrolytic capacitor with high reliability and high specific capacitance, said subsequent processing step is one step or a combination of several steps selected from the group consisting of spherically granulation, heat treatment at high temperature in high vacuum, and deoxidation by magnesium.

3. The process according to claim 2, wherein said raw tantalum powders are tantalum powders subjected to pre-treatment, said pre-treatment is one step or a combination of several steps selected from the group consisting of spherically granulation, heat treatment at high temperature in vacuum, and deoxidation by magnesium.

4. The process according to claim 2, wherein step 2) and step 3) can be repeated at least once.

5. The process according to claim 2, wherein said ball milling is wet ball milling, and ethanol is used as a grinding aid.

6. The process according to claim 2, wherein the acid used for acid washing is an acid or a mixture of several acids selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid, or the acid used for acid washing is a acidic mixture obtained by adding hydrogen peroxide or hydrofluoric acid into the acid selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid.

7. A process for wet ball milling of tantalum powder, in which ethanol is used as a grinding aid in the process, wherein said grinding aid further comprises a surfactant that can improve the dispersion effect of tantalum powder in the grinding aid.

8. A grinding aid for wet ball milling of tantalum powder, consisting of ethanol and a surfactant that can improve the dispersion effect of tantalum powder in the grinding aid.

9. A tantalum powder for use in an electrolytic capacitor with high reliability and high specific capacitance, prepared by a process according to claim 1.

10. An anode for an electrolytic capacitor made of tantalum powder according to claim 9.

11. The process according to claim 1, wherein the ratio of the average particle size of raw tantalum powders to the average particle size of tantalum flake powders is 1.5-10.

12. The process according to claim 1, wherein the ratio of the average particle size of raw tantalum powders to the average particle size of tantalum flake powders is 2-5.

13. The process according to claim 3, wherein a flame retardant is added during the pre-treatment, said flame retardant is selected from the group consisting of substances containing phosphorus, nitrogen, and boron.

14. The process according to claim 13, wherein said flame retardant is selected from the group consisting of ammonium hexafluorophosphate, ammonium dihydrogen phosphate, nitrogen gas and boric acid.

15. The process according to claim 5, wherein ethanol is used as a grinding aid.

16. The process according to claim 15, wherein said grinding aid further comprises a surfactant that can improve the dispersion effect of tantalum powders in the grinding aid.

17. The process according to claim 16, wherein said surfactant is oleic acid, benzoic acid, butanone, polyethylene glycol, isopropanol, cyclohexanol, sodium hexametaphosphate or sodium tripolyphosphate.

18. The process according to claim 16, wherein the added amount of said surfactant is 0.001-50% of the weight of tantalum powder.

19. The process according to claim 16, wherein the added amount of said surfactant is 5-50% of the weight of tantalum powder.

20. The process according to claim 2, wherein the acid used for acid washing is nitric acid in a concentration of 15-35% by weight, or a mixed acid of nitric acid and hydrofluoric acid.

21. The tantalum powder according to claim 9, wherein said tantalum powder is a tantalum flake powder, the content of metal impurities thereof is Fe+Ni+Cr<60 ppm, the content of C thereof is <60 ppm.

22. The tantalum powder according to claim 9, wherein the specific capacitance thereof is 5000-60000 f.Math.V/g, and the formation voltage thereof is 50-270 V.

23. The process according to claim 1, wherein said raw tantalum powders are tantalum powders subjected to pre-treatment, said pre-treatment is one step or a combination of several steps selected from the group consisting of spherically granulation, heat treatment at high temperature in vacuum, and deoxidation by magnesium.

24. The process according to claim 23, wherein a flame retardant is added during the pre-treatment, said flame retardant is selected from the group consisting of substances containing phosphorus, nitrogen, and boron.

25. The process according to claim 24, wherein said flame retardant is selected from the group consisting of ammonium hexafluorophosphate, ammonium dihydrogen phosphate, nitrogen gas and boric acid.

Description

EMBODIMENTS

[0049] The embodiments of the invention are described by combining the following examples. However, a person skilled in the art understands that the following examples are only intended to describe the invention, and shall not be regarded as defining the scope of the invention. When the particular conditions are not indicated in Examples, the invention is carried out according to the conventional conditions or according to conditions suggested by manufacturers. The reagents or apparatuses, the manufacturers of which are not indicated, are the conventional products that are commercially available.

Example 1

[0050] The physical properties of raw tantalum powders used in sample A were shown in table 1, and the content of chemical impurities thereof was shown in table 2. The raw tantalum powders of sample A were sodium-reduced raw powders, which were treated by following method to obtain flake raw powders. The sodium reduction raw powders were blended with 100 ppm phosphorus (i.e. ammonium dihydrogen phosphate, which is converted to 100 ppm of phosphorus content), added with 20% (weight percent) H.sub.2O, vibrated, shook and screened by mesh, pre-agglomerated into granules, then dried, heated in 10.sup.3 Pa vacuum to 1280 C. and held at this temperature for 40 min, then screened to pass through 60 mesh screen, the raw powders passing through 60 mesh screen were stirred and ball milled in a grinding aid (the grinding aid was a mixture obtained by adding oleic acid in an amount of 50% of the weight of the tantalum powders into ethanol (the concentration of ethanol is 99.7%)) for 20 hours to form flakes. The ball milled powders were washed with a mixed acid of HNO.sub.3 and HF (the mixed acid was a mixture of 69% HNO.sub.3 solution, 40% HF solution and water, the volume ratio of HNO.sub.3 solution, HF solution and water is 4:1:20) to remove impurities, then dried, and then screened to obtain flake raw powders. The ratio of the particle size of the raw powders of Sample A to the particle size of the obtained flake raw powders was 2.48.

[0051] The physical properties of the flake raw powders obtained above were shown in Table 1, and the chemical properties thereof were shown in Table 2. The flake raw powders were heated in 10.sup.3 Pa vacuum to 1150 C. and held for 60 minutes, crushed by means of jaw crusher to 50 mesh, subjected to second heat treatment and deoxidation treatment, i.e., heated in 10.sup.3 Pa vacuum to 1300 C. and held for 60 minutes, crushed by means of jaw crusher to 50 mesh, subjected to deoxidation treatment at 900 C., washed with 20% (by weight) HNO.sub.3 to remove magnesium oxide and residual magnesium, dried, and then screened to pass through 50 mesh screen to obtain sample A (i.e. product powders). The chemical impurities of sample A were shown in Table 2.

[0052] Sample A was pressed into pellets, the green density was 5.0 g/cm.sup.3, the weight of pellets was 0.15 g, and the pellets were measured according to the national standard (GBT 3137-2007 test method of tantalum powder electrical property). The pellets were separately sintered at 1300 C., 1350 C., 1400 C. or 1450 C. in 10.sup.3 Pa vacuum oven for 30 minutes to form sintered pellets. The sintered pellets were formed in 0.01% (by weight) phosphoric acid solution at a voltage of 70 V to obtain an anode of capacitor. The electrical properties of the anode were measured and shown in Table 3.

[0053] Sample A was pressed into pellets, the green density was 5.0 g/cm.sup.3, the weight of pellets was 0.15 g. The pellets were measured according to the national standard (GBT 3137-2007 test method of tantalum powder electrical property). The pellets were sintered at 1350 C. in 10.sup.3 Pa vacuum oven for 30 minutes to form sintered pellets. The sintered pellets were formed in 0.01% (by weight) phosphoric acid solution at a voltage of 50V, 70V, or 100V to obtain an anode of capacitor. The electrical properties of the anode were measured and shown in Table 4.

TABLE-US-00002 TABLE 1 physical properties of raw tantalum powders and flake raw powders of sample A Average particle Average particle size of raw size of flake Particle tantalum powders raw powders size sample (m) (m) ratio Sample A 10.7 4.3 2.49

TABLE-US-00003 TABLE 2 comparison of impurities content of raw tantalum powders, flake raw powders and product powders of sample A Powders type Raw tantalum Flake raw Product parameters powders powders powders Fe (ppm) 10 25 26 Ni (ppm) 5 5 6 Cr (ppm) 5 5 5 C (ppm) 15 40 45

TABLE-US-00004 TABLE 3 specific capacitance and leakage current of electrolytic capacitor anode obtained from sample A at different sintering conditions Sintering temperature ( C./min) Property parameters 1300/30 1350/30 1400/30 1450/30 Leakage current I (A/g) 18.2 14.6 12.5 10.6 Capacitance value (F .Math. V/g) 59930 58370 52443 48700

TABLE-US-00005 TABLE 4 specific capacitance and leakage current of electrolytic capacitor anode obtained from sample A at different formation voltage formation voltage (V) Property parameters 50 70 100 Leakage current I (A/g) 8.2 14.6 22.8 Capacitance value (F .Math. V/g) 64730 58370 50420

Example 2

[0054] The physical properties of raw tantalum powders used in sample B were shown in table 5, and the content of chemical impurities thereof was shown in table 6. The raw tantalum powders of sample B were sodium-reduced raw powders, which were treated by following method to obtain flake raw powder. The sodium reduction raw powders were blended with 100 ppm phosphorus (i.e. ammonium dihydrogen phosphate, which is converted to 100 ppm of phosphorus content), heated in 10.sup.3 Pa vacuum to 1360 C. and held at this temperature for 40 minutes, screened to pass through 60 mesh screen, subjected to deoxidation treatment at 900 C., then washed with 20% (by weight) HNO.sub.3 to remove magnesium oxide and residual magnesium, dried, and then screened to pass through 50 mesh screen. The powders passing through 50 mesh screen were stirred and ball milled in a grinding aid (the grinding aid was a mixture obtained by adding oleic acid of 5% (by weight) of the weight of tantalum powders into ethanol (the concentration of ethanol was 99.7%) for 5 hours to form flakes. The ball milled powder were washed with a mixed acid of HNO.sub.3 and HF (the mixed acid was a mixed acid of 69% HNO.sub.3 solution, 40% HF solution and water, the volume ratio of HNO.sub.3 solution, HF solution and water is 4:1:20) to remove metal impurities, then dried, and then screened to obtain flake raw powders. The ratio of the particle size of the raw powders of Sample B to the particle size of the obtained flake raw powders was 4.89.

[0055] The physical properties of the flake raw powders obtained above were shown in Table 5, and the chemical properties thereof were shown in Table 6. The flake raw powders were heated in 10.sup.3 Pa vacuum to 1300 C. and held for 60 minutes, crushed by means of jaw crusher to 50 mesh, subjected to second heat treatment and deoxidation treatment, i.e., heated in 10.sup.3 Pa vacuum to 1450 C. and held for 60 minutes, crushed by means of jaw crusher to 50 mesh, subjected to deoxidation treatment at 900 C., washed with 20% (by weight) HNO.sub.3 to remove magnesium oxide and residual magnesium, dried, and then screened to pass through 50 mesh screen to obtain sample B (i.e. product powders). The content of chemical impurities of sample B was shown in Table 6.

[0056] Sample B was pressed into pellets, the green density was 5.0 g/cm.sup.3, the weight of pellets was 0.15 g. The pellets were measured according to the national standard (GBT 3137-2007 test method of tantalum powder electrical property). The pellets were separately sintered at 1450 C., 1500 C., 1550 C. or 1600 C. in 10.sup.3 Pa vacuum oven for 30 minutes to form sintered pellets. The sintered pellets were formed in 0.01% (by weight) phosphoric acid solution at a voltage of 140 V to obtain an anode of capacitor. The electrical properties of the anode were measured and shown in Table 7.

[0057] Sample B was pressed into pellets, the green density was 5.0 g/cm.sup.3, the weight of pellets was 0.15 g. The pellets were measured according to the national standard (GBT 3137-2007 test method of tantalum powder electrical property). The pellets were sintered at 1500 C. in 10.sup.3 Pa vacuum oven for 30 minutes to form sintered pellets. The sintered pellets were formed in 0.01% (by weight) phosphoric acid solution at a voltage of 100V, 140V or 200V to obtain an anode of capacitor. The electrical properties of the anode were measured and shown in Table 8.

TABLE-US-00006 TABLE 5 physical properties of raw tantalum powders and flake raw powders of sample B Average particle Average particle size of raw size of flake Particle tantalum powder raw powder size sample (m) (m) ratio Sample B 35.2 7.2 4.89

TABLE-US-00007 TABLE 6 comparison of impurities content of raw tantalum powders, flake raw powders and product powders of sample B Powders type Raw Flake Product parameters tantalum powders Raw powders powders Fe (ppm) 8 25 27 Ni (ppm) 5 5 5 Cr (ppm) 5 5 5 C (ppm) 15 46 47

TABLE-US-00008 TABLE 7 specific capacitance and leakage current of electrolytic capacitor anode obtained from sample B at different sintering conditions Sintering temperature ( C./min) Property parameters 1450/30 1500/30 1550/30 1600/30 Leakage current I (A/g) 6.1 5.8 3.3 3.0 Capacitance value (F .Math. V/g) 28500 21727 19888 17800

TABLE-US-00009 TABLE 8 specific capacitance and leakage current of electrolytic capacitor anode obtained from sample B at different formation voltage formation voltage (V) Property parameters 100 140 200 Leakage current I (A/g) 4.6 5.8 7.3 Capacitance value (F .Math. V/g) 26460 21727 16800

Example 3

[0058] Raw tantalum powders used in sample C and sample D were sodium-reduced raw powders, physical properties thereof were shown in table 9 and the content of chemical impurities thereof was shown in table 10. The raw tantalum powders were treated by following method to obtain flake raw powders. The sodium reduction raw powders were blended with 100 ppm phosphorus (i.e. ammonium dihydrogen phosphate, which is converted to 100 ppm of phosphorus content), added with 20% (weight percent) H.sub.2O, vibrated shook and screened by mesh, pre-pelletized into granules, dried, heated in 10.sup.3 Pa vacuum to 1360 C. and held at this temperature for 40 minutes, then screened to pass through 60 mesh screen, and then subjected to deoxidation treatment at 900 C., washed with 20% (by weight) HNO.sub.3 to remove magnesium oxide and residual magnesium, dried, screened to pass through 50 mesh screen. The powders passing through 50 mesh screen were stirred and ball milled, wherein: sample C was ball milled in a grinding aid (the grinding aid was a mixture obtained by adding oleic acid of 20% (by weight) of the weight of tantalum powders into ethanol (the concentration of ethanol was 99.7%) for 12 hours to form flakes; sample D was ball milled in a grinding aid (the grinding aid was a mixture obtained by adding benzoic acid of 20% (by weight) of the weight of tantalum powders into ethanol (the concentration of ethanol was 99.7%) for 12 hours to form flakes. The ball milled powder was separately washed with a mixed acid of HNO.sub.3 and HF (the mixed acid was a mixture of 69% HNO.sub.3 solution, 40% HF solution and water, the volume ratio of HNO.sub.3 solution, HF solution and water is 4:1:20) to remove metal impurities, dried and then screened to obtain flake raw powders. The ratio of the particle size of the raw powders of Sample C to the particle size of the obtained flake raw powders was 4.32. The ratio of the particle size of the raw powders of Sample D to the particle size of the obtained flake raw powders was 4.10.

[0059] The physical properties of the flake raw powders obtained above were shown in Table 9, and the chemical properties thereof were shown in Table 10. The flake raw powders were separately heated in 10.sup.3 Pa vacuum to 1200 C. and held for 60 minutes, crushed by means of jaw crusher to 50 mesh, then subjected to second heat treatment and deoxidation treatment, i.e., heated in 10.sup.3 Pa vacuum to 1400 C. and held for 60 minutes, crushed by means of jaw crusher to 50 mesh, subjected to deoxidation treatment at 900 C., washed with 20% (by weight) HNO.sub.3 to remove magnesium oxide and residual magnesium, dried, and then screened to pass through 50 mesh screen to obtain sample C and sample D (i.e. product powders). The contents of chemical impurities of sample C and sample D were shown in Table 10.

[0060] Sample C and sample D were separately pressed into pellets, the green density was 5.0 g/cm.sup.3, the weight of pellets was 0.15 g. The pellets were separately measured according to the national standard (GBT 3137-2007 test method of tantalum powder electrical property). The pellets were separately sintered at 1400 C., 1450 C. or 1500 C. in 10.sup.3 Pa vacuum oven for 30 minutes to form sintered pellets. The sintered pellets were separately formed in 0.01% (by weight) phosphoric acid solution at a voltage of 100 V to obtain two anodes of capacitors. The electrical properties of the two anodes were measured and shown in Table 11.

[0061] Sample C and sample D were separately compacted into pellets, the green density was 5.0 g/cm.sup.3, the weight of pellets was 0.15 g. The pellets were separately measured according to the national standard (GBT 3137-2007 test method of tantalum powder electrical property). The pellets were separately sintered at 1400 C. in 10.sup.3 Pa vacuum oven for 30 minutes to form sintered pellets. The sintered pellets were energized in 0.01% (by weight) phosphoric acid solution at a voltage of 70V, 100V or 140V to obtain two anodes of capacitors. The electrical properties of the two anodes were measured and shown in Table 12.

TABLE-US-00010 TABLE 9 physical properties of raw tantalum powders and flake raw powders of sample C, sample D or sample E Average particle Average particle size of raw size of flake Particle tantalum powders raw powders size sample (m) (m) ratio Sample C 22.2 5.14 4.32 Sample D 22.2 5.42 4.10 Sample E (do not 128.6 5.02 25.62 belong to the present invention

TABLE-US-00011 TABLE 10 comparison of impurities content of raw tantalum powders, flake raw powders and product powders of sample C, sample D or sample E Powder type Raw Flake Product parameters tantalum powders Raw powders powders Sample C Fe (ppm) 11 18 22 Ni (ppm) 5 5 5 Cr (ppm) 4 5 5 C (ppm) 16 35 38 Sample D Fe (ppm) 11 20 23 Ni (ppm) 5 5 5 Cr (ppm) 4 5 5 C (ppm) 16 40 42 Sample E Fe (ppm) 9 69 72 Ni (ppm) 6 30 31 Cr (ppm) 7 19 19 C (ppm) 16 86 89

TABLE-US-00012 TABLE 11 specific capacitance and leakage current of electrolytic capacitor anode obtained from samples C, D or E at different sintering conditions Sample Sintering temperature ( C./min) number Property parameters 1400/30 1450/30 1500/30 1550/30 C Leakage current I (A/g) 13.3 8.7 6.5 5.0 Capacitance value 38526 36150 33653 28700 (F .Math. V/g) D Leakage current I (A/g) 15.1 9.1 7.4 6.1 Capacitance value 37320 35520 32450 26980 (F .Math. V/g) E Leakage current I (A/g) 28.7 23.3 18.4 6.8 Capacitance value 31585 23551 19535 22401 (F .Math. V/g)

TABLE-US-00013 TABLE 12 specific capacitance and leakage current of electrolytic capacitor anode obtained from samples C, D or E at different formation voltage Sample formation voltage (V) number Property parameter 70 100 140 C Leakage current I (A/g) 8.1 13.3 17.8 Capacitance value (F .Math. V/g) 40930 38526 23420 D Leakage current I (A/g) 8.9 15.1 19.8 Capacitance value (F .Math. V/g) 39092 37320 22054 E Leakage current I (A/g) 12.3 18.7 23.8 Capacitance value (F .Math. V/g) 37020 36585 19887

Comparative Example 1

[0062] Sample E was produced by the process for producing tantalum flake powders described in U.S. Pat. No. 5,580,367. Sodium-reduced raw powders were subjected to pass through 60 mesh screen, the physical properties of the employed sodium-reduced raw powders were shown in Table 9, and the chemical properties thereof were shown in Table 10. Screened sodium reduction raw powders, which was not subjected heat treatment, were directly stirred and ball milled in a grinding aid (the grinding aid was a mixture obtained by adding oleic acid of 20% (by weight) of the weight of tantalum powder into ethanol (the concentration of ethanol was 99.7%) for 12 hours to form flakes. It was found by analysis that after ball milled, the particle size was 30.6 m, ball milling was continuously carried out for 36 hours. The ball milled powders was washed with a mixed acid of HNO.sub.3 and HF (the mixed acid was a mixture of 69% HNO.sub.3 solution, 40% HF solution and water, the volume ratio of HNO.sub.3 solution, HF solution and water is 4:1:20) to remove metal impurities, dried with and then screened to obtain flake raw powders of sample E. The ratio of the particle size of the raw powders of Sample E to the particle size of the obtained flake raw powders was 4.32.

[0063] The physical properties of the flake raw powders obtained above were shown in Table 9, and the chemical properties thereof were shown in Table 10. The flake raw powders of sample E were heated in a sealed container to about 850 C., hydrogen was introduced to lower the temperature to room temperature and to carry out hydrogenation. The hydrogenated flake raw powders were impacted by jet mill into small flakes. The small flakes were heated in 10.sup.3 Pa vacuum to 1200 C. and held for 60 minutes, crushed by means of jaw crusher to 50 mesh, subjected to second heat treatment and deoxidation treatment, i.e., heated in 10.sup.3 Pa vacuum to 1400 C. and held for 60 minutes, crushed by means of jaw crusher to 50 mesh, subjected to deoxidation treatment at 900 C., washed with 20% (by weight) HNO.sub.3 to remove magnesium oxide and residual magnesium, dried, and then screened to pass through 50 mesh screen to obtain sample E (i.e. product powders). The content of chemical impurities of sample E was shown in Table 10.

[0064] Like sample C and sample D, sample E was pressed into pellets, the green density was 5.0 g/cm.sup.3, the weight of pellets was 0.15 g. The pellets were measured according to the national standard (GBT 3137-2007 test method of tantalum powder electrical property). The pellets were separately sintered at 1400 C., 1450 C. or 1500 C. in 10.sup.3 Pa vacuum oven for 30 minutes to form sintered pellets. The sintered pellets were formed in 0.01% (by weight) phosphoric acid solution at a voltage of 100 V to obtain an anode of capacitor. The electrical properties of the anode were measured and shown in Table 11.

[0065] Like sample C and sample D, sample E was pressed into pellets, the green density was 5.0/cm.sup.3, the weight of pellets was 0.15 g. The pellets were measured according to the national standard (GBT 3137-2007 test method of tantalum powder electrical property). The pellets were sintered at 1400 C. in 10.sup.3 Pa vacuum oven for 30 minutes to form sintered pellets. The sintered pellets were formed in 0.01% (by weight) phosphoric acid solution at a voltage of 100V, 140V or 200V to obtain an anode of capacitor. The electrical properties of the anode were measured and shown in Table 12.

[0066] It can be seen by comparison that the impurities amounts of samples C and D are obviously less than those of sample E, the leakage current of electrolytic capacitor anode obtained from sample C or sample D is obviously less than that of the anode prepared from sample E, while the specific capacitance of the electrolytic capacitor anode obtained from sample C or sample D is obviously higher than that of the anode prepared from sample E.

[0067] It is clearly seen from the comparative data in Tables 1-12 that the smaller the average particle size of raw materials is, the smaller the average particle size of the tantalum flake powders obtained after ball milled is. The ratio of the particle size of raw materials to the particle size of flake powders was controlled between 2 and 5, the tantalum powders obtained are used to prepare the anode of electrolytic capacitor, which has higher specific capacitance and lower leakage current.

[0068] It can be seen from above examples that the anode of electrolytic capacitor anode manufactured by the tantalum powder obtained in the present invention has high specific capacitance and low leakage current at high sintering temperature and under high formation voltage.