Method of forming a piezoelectric actuator

1. A method of forming a piezoelectric actuator, comprising:

providing a stack having piezoelectric layers and electrode layers arranged between the piezoelectric layers;

placing an outer electrode onto an outer side of the stack; and

thermally spraying a material onto parts of an upper side of the outer electrode and the outer side of the stack;

wherein the material forms a bonding layer on the parts of the outer electrode and outer side of the stack.

2. The method according to claim 1 , wherein thermally spraying the material comprises performing a method selected from the group consisting of flame spraying, plasma spraying, cold-gas spraying and arc spraying.

3. The method according to claim 2 , wherein a temperature of the stack during the thermal spraying is below a melting temperature of the material.

4. The method according to claim 3 , wherein the temperature of the stack is less than 200° C. during the thermally spraying the material.

5. The method according to claim 4 , wherein the thermally spraying comprises thermally spraying the material at a temperature and speed that, when the material impinges on a surface of the outer electrode or the stack, particles of the material bond to one another and to the surface to form the bonding layer.

6. The method according to claim 1 , wherein the material comprises an electrically conductive material.

7. The method according to claim 6 , wherein the material comprises a metal.

8. The method according to claim 7 , wherein the metal is selected from the group consisting of copper, silver, aluminum and tin.

9. The method according to claim 1 , wherein the outer electrode comprises holes and wherein thermally spraying the material comprises spraying the material into the holes.

10. The method according to claim 1 , further comprising sintering the stack prior to the thermally spraying.

11. The method according to claim 10 , wherein all layers of the stack are sintered at one and the same time.

12. The method according to claim 1 , wherein the bonding layer extends contiguously from past a first edge of the outer electrode over an upper side of the bonding layer and past a second edge of the outer electrode opposite the first edge;

wherein the bonding layer extends past a third edge of the outer electrode at a first end of the outer electrode, wherein the third edge is adjacent to the first edge and the second edge; and

wherein a second end of the outer electrode opposite the first end extends past the bonding layer such a first portion of the outer electrode is free of the bonding layer.

13. The method according to claim 12 , further comprising mounting a lead on, and electrically connected to, the outer electrode;

wherein the lead is fastened to the upper side of the first portion of the outer electrode.

14. The method according to claim 12 , further comprising mounting a lead on, and electrically connected to, an outer surface of the bonding layer.

15. The method according to claim 1 , further comprising:

providing a contact layer on the outer side of the stack, the contact layer for electrical contacting the electrode layers; and

wherein the placing an outer electrode onto an outer side of the stack comprises placing the outer electrode on the contact layer.

16. The method according to claim 1 , wherein the bonding layer bonds to the entire upper side of the outer electrode.

17. The method according to claim 1 , wherein the outer electrode comprises a wire fabric.

18. A method of forming a piezoelectric actuator, comprising:

providing a stack comprising piezoelectric layers and electrode layers arranged between the piezoelectric layers;

providing an outer electrode;

fastening the outer electrode to the stack by applying a bonding layer by thermal spraying.

19. The method according to claim 18 , wherein the outer electrode comprises a wire fabric.