Phase stable doped zirconia electrolyte compositions with low degradation

1. A scandia stabilized zirconia electrolyte composition for a solid oxide fuel cell, comprising;

a formula (ZrO 2 ) 1-w-x-b (Sc 2 O 3 ) w (CeO 2 ) x (Yb 2 O 3 ) b , where:

w=0.1; x=0.01 and b=0.01; or

w=0.1; x=0.01 and b=0.005; or

w=0.1; x=0.005 and b=0.005;

wherein:

the scandia stabilized zirconia electrolyte composition consists of a single layer located in direct contact with an anode on a first major surface of the single layer and in direct contact with a cathode on a second major surface of the single layer;

the composition does not experience a degradation of ionic conductivity of greater than 15% after 4000 hrs and at a temperature of 850° C.;

the composition comprises a cubic phase which substantially lacks tetragonal phase domains after operating in a solid oxide fuel cell at 850° C. for at least 4000 hours in at least one of air or hydrogen ambient; and

the composition does not experience a cubic to rhombohedral phase transition at a temperature of about 25 to 850° C.

2. The composition of claim 1 , wherein:

the composition is utilized as an electrolyte layer of a planar solid oxide fuel cell comprising the anode and the cathode;

the electrolyte layer supports the anode and cathode;

the solid oxide fuel cell is located in a solid oxide fuel cell stack adjacent to an interconnect comprising at least 94 wt % Cr, 4-6 wt % Fe and 0-1 wt % Y; and

a coefficient of thermal expansion of the electrolyte differs by 1% or less from a coefficient of thermal expansion of the interconnect.

3. The composition of claim 1 , wherein w=0.1; x=0.01 and b=0.01.

4. The composition of claim 1 , wherein w=0.1; x=0.01 and b=0.005.

5. The composition of claim 1 , wherein w=0.1; x=0.005 and b=0.005.

6. A scandia stabilized zirconia electrolyte composition for a solid oxide fuel cell, comprising a formula (ZrO 2 ) 1-w-x-b (Sc 2 O 3 ) w (CeO 2 ) x (Yb 2 O 3 ) b , where:

0.09≦w≦0.11; 0.005<x<0.015 and 0.0025<b≦0.015;

wherein:

the scandia stabilized zirconia electrolyte composition consists of a single layer located in direct contact with an anode on a first major surface of the single layer and in direct contact with a cathode on a second major surface of the single layer;

the composition does not experience a degradation of ionic conductivity of greater than 15% after 4000 hrs and at a temperature of 850° C.;

the composition comprises a cubic phase which substantially lacks tetragonal phase domains after operating in a solid oxide fuel cell at 850° C. for at least 4000 hours in at least one of air or hydrogen ambient; and

the composition does not experience a cubic to rhombohedral phase transition at a temperature of about 25 to 850° C.

7. The composition of claim 6 , wherein:

0.01≦x≦0.015 and 0.005≦b≦0.0125.

8. The composition of claim 7 , wherein:

0.005≦b≦0.01.

9. The composition of claim 8 , wherein:

w=0.1, b=0.01 and x=0.01.

10. The composition of claim 6 , wherein:

0.005≦x≦0.0125 and 0.0025≦b≦0.01.

11. The composition of claim 6 , wherein:

0.0025≦b≦0.0125.

12. The composition of claim 11 , wherein:

0.005≦x≦0.01 and 0.005≦b≦0.01.

13. The composition of claim 8 , wherein:

w=0.1 and x=0.01.

14. A planar fuel cell comprising the electrolyte of the composition of claim 6 .

15. A scandia stabilized zirconia electrolyte composition for a solid oxide fuel cell, comprising:

a formula (ZrO 2 ) 1-w-x-b (Sc 2 O 3 ) w (CeO 2 ) x (Yb 2 O 3 ) b , where w=0.1; x=0.01 and b=0.01;

wherein:

the scandia stabilized zirconia electrolyte composition consists of a single layer located in direct contact with an anode on a first major surface of the single layer and in direct contact with a cathode on a second major surface of the single layer;

the composition experiences a degradation of ionic conductivity of 1-5% after 4000 hrs and at a temperature of 850° C.;

the composition comprises a cubic phase which substantially lacks tetragonal phase domains after operating in a solid oxide fuel cell at 850° C. for at least 4000 hours in at least one of air or hydrogen ambient; and

the composition does not experience a cubic to rhombohedral phase transition at a temperature of about 25 to 850° C.

16. The composition of claim 15 , wherein the composition have a starting ionic conductivity of 0.14 S/cm or greater.

17. The composition of claim 16 , wherein the composition have a starting ionic conductivity of 0.16 to 0.17 S/cm.