Tantalum powder and method of making the same

Abstract

Tantalum powder capable of producing anodes of improved electrical capacitance is prepared by the addition of phosphorus-containing materials in amounts from about 5 to about 400 ppm based on elemental phosphorus. In one embodiment, the flow properties of the powder are also improved.

What is claimed is: .[.1. A tantalum powder containing an added phosphorus-containing material in an amount equivalent to from about 5 to about 400 parts per million of elemental phosphorus..]. .[.2. A tantalum powder in accordance with claim 1 in which the powder particles are agglomerated..]. .[.3. A tantalum powder in accordance with claim 1 in which the powder particles are unagglomerated..]. .[.4. A tantalum powder in accordance with claim 2 in which said phosphorus-containing material is added to said tantalum powder prior to the agglomeration thereof..]. .[.5. A tantalum powder in accordance with claim 2 in which said phosphorus-containing material is added to said tantalum powder after the 
     
        agglomeration thereof..]. .[.6.  A tantalum powder in accordance with claim 2 in which at least a portion of said phosphorus-containing material is calcium orthophosphate, added after agglomeration in an amount equivalent to from about 20 to about 80 parts per million of elemental phosphorus..]. .[.7. A tantalum powder in accordance with claim 1 in which the phosphorus-containing material is free of metallic cations..]. .[.8. A tantalum powder in accordance with claim 2 in which a major portion of the phosphorus in said powder is obtained by the addition of a phosphorus-containing material having no metallic cations and a minor portion is obtained by the addition of calcium orthophosphate after agglomeration in an amount not exceeding about 80 parts per million of 
     
     
        elemental phosphorus..]. 9. A tantalum powder in accordance with claim .[.1.]. .Iadd.32 .Iaddend.in which at least a major portion of said phosphorus-containing material is added in the form of an orthophosphate compound of the group consisting of ammonium orthophosphate, ammonium hydrogen orthophosphate, ammonium di-hydrogen orthophosphate, and orthophosphoric acid. .[.10. A tantalum anode prepared by pressing and sintering the tantalum powder of claim 1..]. .[.11. A tantalum anode prepared by pressing tantalum powder into the shape of an anode, adding to said pressed tantalum powder a phosphorus-containing material in an amount equivalent to from about 5 to about 400 parts per million of elemental phosphorus, and thereafter sintering said pressed tantalum powder..]. .[.12. A method of improving a tantalum powder which comprises adding to said powder an amount of a phosphrous-containing material corresponding to from about 5 to about 400 parts per million of phosphorus..]. .[.13. A method in accordance with claim 1 in which said tantalum powder is agglomerated prior to the addition of said phosphorus-containing material..]. .[.14. A method in accordance with claim 12 in which said phosphorus-containing material is added to said powder prior to agglomeration..]. .[.15. A method in accordance with claim 12 in which said phosphorus-containing material comprises a minor proportion of calcium orthophosphate and a larger proportion of a phosphorus-containing material having no metallic cations, said calcium orthophosphate being added after agglomeration in an amount equivalent to from about 20 to 
     
     
        about 80 parts per million of elemental phosphorus..]. 16. A method of improving a tantalum powder which comprises adding to said powder while it is in the form of tantalum hydride an amount of phosphorus-containing material corresponding to from about .[.5.]. .Iadd.37.5 to about 400 parts per million of phosphorus and thereafter converting said tantalum hydride 
     
     
        to metallic tantalum. 17. A method in accordance with claim 16 in which said tantalum hydride is converted to metallic tantalum during 
     
     
        agglomeration. 18. A method in accordance with claim 16 in which said tantalum hydride is converted to metallic tantalum and thereafter agglomerated. .[.19. A method of forming an improved tantalum anode which comprises pressing and sintering the tantalum powder of claim 1..]. .[.20. A method of forming an improved tantalum anode which comprises pressing a tantalum powder into the shape of an aode, adding to said pressed tantalum powder to phosphorus-containing material in an amount equivalent to from about 5 to about 400 parts per million of elemental phosphorus, and 
     
     
        thereafter sintering said pressed tantalum powder..]. .Iadd.21.  A method of increasing the specific capacitance of a tantalum powder which comprises adding to said powder an amount of a phosphorus-containing material sufficient to provide an improved level of specific capacitance, the amount of added phosphorus-containing material being within the range corresponding to from about 5 to about 400 parts per million of phosphorus, said phosphorus-containing material comprising a minor proportion of calcium orthophosphate and a larger proportion of a phosphorus-containing material having no metallic cations, said calcium orthophosphate being added after agglomeration in an amount equivalent to from about 20 to about 80 parts per million of elemental phosphorus..Iaddend. .Iadd.22. A tantalum powder containing an added phosphorus-containing material in an amount equivalent to from about 37.5 to about 400 parts per million of elemental phosphorus..Iaddend. 
     
     
        .Iadd.     A tantalum powder as in claim 22 containing an added phosphorus-containing material in an amount equivalent to at least about 50 parts per million of elemental phosphorus..Iaddend. .Iadd.24. A tantalum powder as in claim 22 containing an added phosphorus-containing material in an amount equivalent to at least 65 parts per million of elemental phosphorus..Iaddend. .Iadd.25. A tantalum anode prepared by pressing and sintering the tantalum powder of claim 22..Iaddend. 
     
     
        .Iadd.     A method of improving the specific capacity of tantalum powder for use in making tantalum anodes comprising adding to tantalum powder an amount of an ammonium hydrogen phosphate, within the range equivalent to from about 20 to about 400 parts per million of elemental phosphorus, sufficient to improve the specific capacity (CV/g) of the untreated tantalum by at least about 8.9% when pressed in the forms of anodes and sintered at 1800° C..Iaddend. .Iadd.27. A method of improving the specific capacity of tantalum powder for use in making tantalum anodes comprising adding to tantalum powder, which is in the form of tantalum hydride prior to reduction to metallic tantalum, an amount of phosphorus-containing material, within the range equivalent to from about 37.5 to about 400 parts per million of elemental phosphorus, sufficient to improve the specific capacity (CV/g) of the untreated tantalum by at least 5.2% when pressed in the form of anodes and sintered at 1800° C. 
     
     
        .Iadd.28.  A method of forming an improved tantalum anode having improved capacitance which comprises pressing a tantalum powder into the shape of an anode, adding to said pressed tantalum powder an amount of a phosphorus-containing material sufficient to provide the improved level of specific capacitance, said phosphorus-containing material being added in an amount equivalent to from about 37.5 to about 400 parts per million of elemental phosphorus and thereafter sintering said pressed tantalum powder..Iaddend. .Iadd.29. A method of improving the specific capacity of tantalum powder for use in making tantalum anodes comprising adding to tantalum powder an amount of phosphorus-containing material, within the range equivalent to from about 50 to about 400 parts per million of elemental phosphorus, sufficient to improve the specific capacity (CV/g) of the untreated tantalum by at least 5.2% when pressed in the form of 
     
     
        anodes and sintered at 1800° C..Iaddend. .Iadd.30.  A method as in claim 29 in which the phosphorus-containing material is present in an amount equivalent to at least about 65 parts per million of elemental phosphorus..Iaddend. .Iadd.31. A tantalum powder characterized by increased specific capacitance and improved flow characteristics containing calcium orthophosphate added after agglomeration in an amount equivalent to about 20 to about 80 parts per million of elemental phosphorus..Iaddend. .Iadd.32. A tantalum powder characterized by increased specific capacitance containing an added phosphorus-containing material which is free of metallic cations in an amount equivalent to from about 5 to about 400 parts per million of elemental phosphorus..Iaddend. 
     
     
        .Iadd.33.  A tantalum powder characterized by increased specific capacitance and improved flow properties containing an added phosphorus material which is comprised of a phosphorus-containing material having no metallic cations and a minor amount, not exceeding about 80 parts per million of elemental phosphorus, of calcium orthophosphate added after agglomeration, the total amount of added phosphorus-containing material being in an amount equivalent to from about 5 to about 400 parts per million of elemental phosphorus..Iaddend. .Iadd.34. A method of improving the specific capacity of tantalum powder for use in making tantalum anodes comprising adding to tantalum powder an amount of phosphorus-containing material, within the range equivalent to from about 37.5 to about 400 parts per million of elemental phosphorus, sufficient to improve the specific capacity (CV/g) of the untreated tantalum by at least about 5.2% when pressed in the form of anodes and sintered at 1800° 
     
     
        C..Iaddend. .Iadd.35.  A method in accordance with claim 34 in which the phosphorus-containing material is phosphoric acid..Iaddend. .Iadd.36. A method in accordance with claim 34 in which the phosphorus-containing material is added to tantalum powder which is in the form of metallic tantalum..Iaddend.