Sensor element, sensor arrangement, and method for manufacturing a sensor element and a sensor arrangement

1. A sensor element comprising:

a ceramic main body;

at least one electrode arranged directly at the ceramic main body, wherein the electrode comprises an electrode base which directly overlaps with the ceramic main body and which is partially covered by a surface layer; and

at least one contact piece in form of a separate contact element electrical contacting the electrode,

wherein the contact piece is fastened to a part of the electrode base which is free from the surface layer,

wherein the surface layer is an oxidation preventing surface layer for exposed parts of the electrode base,

wherein the surface layer comprises an oxidation inhibiting metal selected from the group consisting of silver, gold, copper and aluminum, and

wherein the surface layer is a sputtered layer and has a thickness in the range of 0.05 μm to 20 μm.

2. The sensor element according to claim 1 , wherein the contact piece is fastened by gap welding, thermode welding or laser welding.

3. The sensor element according to claim 1 , wherein the contact piece is fastened to the electrode base by thick-wire bonding or thin-wire bonding.

4. The sensor element according to claim 1 , wherein the contact piece comprises a metal from the group consisting of Cu, Fe and Ni.

5. The sensor element according to claim 1 , wherein the electrode has at least one layer which is formed by a burnt-in paste.

6. The sensor element according to claim 1 , wherein the electrode has at least one sputtered layer.

7. The sensor element according to claim 6 , wherein the sputtered layer comprises nickel.

8. The sensor element according to claim 1 , wherein the electrode base has multiple layers which are arranged directly one above the other.

9. The sensor element according to claim 8 , wherein the electrode base has a layer comprising nickel.

10. The sensor element according to claim 9 , wherein the contact piece is fastened to a layer which is partially covered by the surface layer.

11. A sensor arrangement comprising:

the sensor element according to claim 1 ; and

a support for supporting the ceramic main body.

12. The sensor arrangement according to claim 11 , wherein the contact piece is a separate wire connecting the sensor element with the support.

13. The sensor arrangement according to claim 11 , wherein the contact piece forms an integral constituent part of the support.

14. The sensor arrangement according to claim 11 , wherein the support is a circuit board or has at least one thick wire.

15. The sensor arrangement according to claim 11 , wherein the support comprises two support elements, wherein the sensor element comprises two electrodes and two contact elements, and wherein each of the contact elements connects one of the electrodes with one of the support elements.

16. The sensor arrangement according to claim 15 , wherein the contact elements are thick wires or bars.

17. The sensor arrangement according to claim 11 , wherein the support has a rod-shaped form.

18. The sensor arrangement according to claim 11 , wherein the support comprises a ceramic having at least one metallization for electrically connecting the electrode.

19. A method for producing the sensor element according to claim 16 , the method comprising:

fastening the at least one contact piece to the electrode base, which is partially covered by the surface layer, wherein the electrode base, which is partially covered by the surface layer, is arranged at the ceramic main body.

20. A sensor element, comprising:

a ceramic main body; and

at least one electrode arranged at the ceramic main body, each electrode of the least one electrode comprising an electrode base, which directly overlaps with the ceramic main body and a surface layer, wherein the electrode base a part of the electrode situated under the surface layer, wherein the surface layer covers the entire surface of the electrode base except for a part of the electrode base to which at least one contact piece is fastened;

wherein the at least one contact piece is in the form of a separate contact element and is suited for electrically contacting the electrode;

wherein the surface layer is an oxidation-preventing surface layer for parts of the electrode base which are not covered by the contact element;

wherein the surface layer comprises an oxidation-inhibiting metal selected from the group consisting of silver, gold, copper and aluminium; and

wherein the surface layer is a sputtered layer and has a thickness in the range of 0.05 μm to 20 μm.

21. A sensor element, comprising:

a ceramic main body;

two electrodes are arranged directly at the ceramic main body wherein each electrode comprises an electrode base which directly overlaps with the ceramic main body and which is partially covered by a surface layer; and

at least two contact pieces in the form of a separate contact element for electrically contacting each electrode;

wherein each contact piece is fastened to a part of each electrode base of each electrode, which is free from the surface layer;

wherein the surface layer is an oxidation-preventing surface layer for exposed parts of the electrode base;

wherein the surface layer comprises an oxidation-inhibiting metal selected from the group consisting of silver, gold, copper and aluminium; and

wherein the surface layer is a sputtered layer of substantially constant thickness and has a thickness in the range of 0.05 μm to 20 μm.

22. The sensor element according to claim 21 , wherein the surface layer is mainly flat.