Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

• US 5,389,456 A
• Filed: 02/14/1994
• Issued: 02/14/1995
• Est. Priority Date: 02/14/1994
• Status: Expired due to Term

• Current Assignee: Siemens Energy Incorporated (Siemens AG)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Ruka, Roswell J., Singh, Prabhakar
• Primary Examiner(s): Skapars, Anthony
• Application Number:
  US08/195,935
• Time in Patent Office: 365 Days
• Field of Search: 429/30-33, 429/27, 29/623.5, 29/623.2, 427/115, 427/126.3, 427/446, 427/453
• US Class Current: 429/488
• CPC Class Codes: C23C 4/18 After-treatment
• CPC Class Codes: H01M 2008/1293 Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 2300/0074 Ion conductive at high temperature
• CPC Class Codes: H01M 8/0215 Glass; Ceramic materials
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y10T 29/49115 including coating or impregnating

Abstract

A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO₃ particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO₃ particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr₂ O₃ on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO₃ layer coated with CaO and Cr₂ O₃ surface deposit at from about 1000° C. to 1200° C. to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO₃ layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power.

Claims

1. A method of forming a dense, substantially gas-tight, electrically conductive interconnection layer on a porous electrically conductive electrode structure, comprising the steps of:

a. providing an electrode structure;

b. forming by thermal spraying a doped LaCrO₃ powder, on a selected portion of the electrode structure, a layer of porous, doped LaCrO₃ interconnection material bonded to the electrode surface;

c. depositing on the surface of said porous, doped LaCrO₃ layer a mixture comprising CaO and Cr₂ O₃ capable of forming, in part, liquid CaCrO₄ upon heating; and

,

d. heating said porous, doped LaCrO₃ layer with the CaO and Cr₂ O₃ surface deposit in air at from about 1000°

C. to 1200°

C. to form, in part, liquid CaCrO₄, such that the pores of said porous thermally sprayed porous doped LaCrO₃ interconnection layer are substantially closed, at least on the surface, to provide a dense, substantially gas-tight, electrically conductive interconnection material bonded to the electrode surface.

2. The method of claim 1 wherein the doped LaCrO₃ layer of step b) and step d) each independently have the general formula La_1-x M_x Cr_1-y N_y O₃, where M is a dopant selected from the group consisting of Ca, Sr, Ba, and mixtures thereof, N is a dopant selected from the group consisting of Mg, Co, Ni, Al, and mixtures thereof, and, x and y are each independently about 0.01-0.25.

3. The method of claim 1, wherein the heating step d) is from about 1100°

to 1200°

C.

4. The method of claim 1, wherein the heating of step d) closes the pores of the porous, doped LaCrO₃ layer substantially at the surface.

5. The method of claim 1, wherein the electrode is an air electrode, a solid oxide electrolyte is applied to the unselected portion of the electrode surface, and wherein a fuel electrode is applied to the solid electrolyte, to form an electrochemical cell.

6. The method of claim 5, wherein the heating of step d) closes the pores of the porous, doped LaCrO₃ layer substantially at the surface facing the fuel electrode.

7. The method of claim 5, wherein the air electrode is porous, doped LaMnO₃, the solid oxide electrolyte is substantially gas-tight, yttria stabilized ZrO₂, and the fuel electrode is porous, nickel-zirconia cermet.

8. The method of claim 1, wherein the electrode structure is generally tubular.

9. The method of claim 1, wherein the electrode structure is generally planar.

10. The method of claim 1, wherein the thermal spraying of step (b) comprises plasma arc spraying.

12. The method of claim 1, wherein the CaO and Cr₂ O₃ is deposited in step (c) using a tape.

13. The method of claim 1, wherein the doped LaCrO₃ powder of step (b) is agglomerated.

14. The method of claim 1, wherein the doped LaCrO₃ powder of step (b) is compensated with Cr₂ O₃.

15. The method of claim 1, wherein the doped LaCrO₃ powder of step (b) is compensated with dopant.

16. A dense, substantially gas-tight, thermally sprayed, electrically conductive interconnection layer produced according to claim 1.

11. The method of clairol, wherein the CaO and Cr₂ O₃ is deposited in step (c) using a slurry solution.

17. A method of forming a dense, substantially gas-tight, electrically conductive interconnection layer on a porous electrically conductive electrode structure, comprising the steps of:

a. providing an electrode structure;

b. forming by thermal spraying a doped ABO₃ perovskite powder, on a selected surface portion of the electrode structure, a layer of porous, doped ABO₃ perovskite interconnection material bonded to the electrode surface;

c. depositing on the surface of said porous, doped ABO₃ perovskite layer a mixture comprising CaO and Cr₂ O₃ capable of forming, in part, liquid CaCrO₄ upon heating; and

,

d. heating said porous, doped ABO₃ layer with the CaO and Cr₂ O₃ surface deposit in air at from about 1000°

C. to 1200°

C. to form, in part, liquid CaCrO₄, such that the pores of said porous thermally sprayed porous doped ABO₃ interconnection layer are substantially closed, at least on the surface, to provide a dense, substantially gas-tight, electrically conductive interconnection material bonded to the electrode surface.

18. A high temperature, solid oxide electrolyte electrochemical cell, comprising:

a first electrode;

a solid oxide electrolyte disposed on a first portion of the first electrode;

a second electrode disposed on a portion of the solid electrolyte;

an electrically conductive, substantially gas-tight interconnection material disposed on a second portion of the first electrode for electrical coupling to the cell, said interconnection material comprising a thermally sprayed doped LaCrO₃ layer having pores, and subsequently coated with a mixture of CaO+Cr₂ O₃ and heated to temperatures of about 1000°

C. to 1200°

C. to substantially close the pores, at least on the surface of the thermally sprayed doped LaCrO₃ layer.

19. The high temperature, solid oxide electrolyte electrochemical cell of claim 18, wherein the first electrode is an air electrode and the second electrode is a fuel electrode.