Preparation of yttria-stabilized zirconia reaction sintered products

1. A method of making a reaction sintered yttria stabilized zirconia, the method comprising:

providing separate powders of zirconia, yttria, and a metal oxide and mixing them into a powdered mixture of zirconia, yttria and about 2%, by wt., or less of a metal oxide, wherein yttria-stabilized zirconia is not added to the mixture;

sintering the powdered mixture at about 1500° C. or less, for about 5 hours or less, to form the reaction-sintered yttria stabilized zirconia comprising cubic YSZ.

2. The method of claim 1 , wherein the presintered zirconia comprises monoclinic ZrO 2 .

3. The method of claim 2 , wherein presintered zirconia comprises more of the monoclinic ZrO 2 than cubic ZrO 2 .

4. The method of claim 2 , wherein substantially all the monoclinic ZrO 2 is converted into cubic ZrO 2 during the sintering.

5. The method of claim 1 , wherein the presintered zirconia and yttria are not calcined prior to the sintering.

6. The method of claim 1 , wherein the metal oxide is dissolved in the cubic YSZ to make the reaction-sintered yttria stabilized zirconia a single phase material.

7. The method of claim 1 , wherein the metal oxide is selected from the group consisting of nickel oxide, iron oxide, cobalt oxide, manganese oxide, copper oxide, and mixtures thereof.

8. The method of claim 1 , wherein the metal oxide is nickel oxide.

9. The method of claim 1 , wherein the metal oxide is about 1%, by wt., or less of the powdered mixture.

10. The method of claim 1 , wherein the metal oxide is about 0.5%, by wt., or less of the powdered mixture.

11. The method of claim 1 , wherein the powdered mixture comprises about 3-mol % to about 10-mol % yttria.

12. The method of claim 11 , wherein the powdered mixture comprises about 8-mol % yttria.

13. The method of claim 1 , wherein the reaction sintered yttria-stabilized zirconia forms an electrolyte of a solid oxide fuel cell.

14. The method of claim 13 , wherein the electrolyte is co-sintered with an electrode of the solid oxide fuel cell.

15. The method of claim 14 , wherein the electrode comprises a second reaction sintered yttria stabilized zirconia.

16. The method of claim 15 , wherein the second reaction sintered yttria-stabilized zirconia is formed from a powdered mixture of zirconia, yttria and greater than 2%, by wt., of a metal oxide.

17. The method of claim 16 , wherein the metal oxide is nickel oxide.

18. A method of making a fuel cell electrolyte, the method comprising:

forming a green body comprising separate powders of zirconia, yttria and about 2%, by wt., or less of a metal oxide that are mixed into a powdered mixture, wherein yttria-stabilized zirconia is not added to the green body; and

sintering the green body at about 1500° C. or less to form a reaction sintered body comprising cubic yttria-stabilized zirconia.

19. The method of claim 18 , wherein the green body is formed on an electrode of the fuel cell.

20. The method of claim 19 , wherein the electrode is an anode.

21. The method of claim 19 , wherein the electrode forms a second green body comprising zirconia, yttria and greater than 2%, by wt., of the metal oxide.

22. The method of claim 21 , wherein the metal oxide in the second green body is about 50%, by wt., or more.

23. The method of claim 21 , wherein the electrolyte and the electrode are co-sintered.

24. The method of claim 23 , wherein the co-sintering forms a single phase cubic YSZ in the electrolyte and a two-phase composite of metal oxide and cubic YSZ in the electrode.

25. The method of claim 24 , wherein the electrolyte and the electrode are exposed to a reducing atmosphere to convert at least a portion of the metal oxide into metal.

26. The method of claim 25 , wherein the reducing atmosphere reduces the metal oxide component in the electrode to a conductive metal.

27. The method of claim 25 , wherein the reducing atmosphere comprises hydrogen.

28. The method of claim 18 , wherein the metal oxide is nickel oxide.

29. The method of claim 18 , wherein the green body is sintered for about 5 hours or less.

30. A method of making a ceramic oxide fuel cell, the method comprising:

forming a self-supporting electrode;

forming an electrolyte on the self supporting electrode; and

forming a second electrode on the electrolyte,

wherein the electrolyte is made by:

combining separate powders of zirconia, yttria and about 2%, by wt., or less of a metal oxide, and mixing them into a powdered mixture, wherein yttria-stabilized zirconia is not added to the mixture; and

sintering the mixture at about 1500° C. or less, for about 5 hours or less, to form a reaction sintered yttria-stabilized zirconia and the metal oxide.

31. The method of claim 30 , wherein the ceramic oxide fuel cell is a solid oxide fuel cell.

32. The method of claim 30 , wherein the solid electrolyte fuel cell is a protonic ceramic fuel cell.

33. The method of claim 30 , wherein the metal oxide comprises nickel oxide.

34. The method of claim 30 , wherein the self supporting electrode is formed by:

combining zirconia, yttria and greater than about 50%, by wt., of the metal oxide;

co-sintering the self supporting electrode with the electrolyte, wherein the co-sintering forms a single phase cubic YSZ in the electrolyte and a two-phase composite of metal oxide and cubic YSZ in the electrode; and

reducing at least a portion of the metal oxide in the sintered electrode to conductive metal.