PIEZOELECTRIC CERAMIC, METHOD FOR THE PRODUCTION THEREOF AND ELECTROCERAMIC COMPONENT COMPRISING THE PIEZOCERAMIC

Abstract

A hard lead zirconate titanate (PZT) ceramic of the general structure ABO3 is specified, wherein the PZT ceramic has doping with Mn on the B sites and doping with Cu on the A sites and/or on the B sites. A process for producing a ceramic material and an electroceramic component are moreover specified.

Claims

1. A hard lead zirconate titanate (PZT) ceramic of the general structure ABO3, characterized in that the PZT ceramic has doping with Mn on the B sites and additionally doping with Cu on the A sites and/or on the B sites.

2. The PZT ceramic as claimed in the preceding claim, wherein the A sites have at least one further doping with Na, K, Ag, Nd, La, Ba, Sr, Ca or Bi, preferably Na and/or K.

3. The PZT ceramic as claimed in either of the preceding claims, wherein the B sites have at least one further doping with Fe, Nb, Zn, Ge, Sn, Al, Ga or Sb, preferably Nb.

4. The PZT ceramic as claimed in any of the preceding claims, wherein the doping on the A sites and/or B sites comprises up to 1.0 atom % of Cu, preferably from 0.05 to 0.1 atom % of Cu.

5. The PZT ceramic as claimed in any of the preceding claims, wherein the doping on the B sites comprises up to 5.0 atom % of Mn, preferably from 2.0 to 3.0 atom % of Mn.

6. The PZT ceramic as claimed in any of the preceding claims, wherein the ceramic has a general formula (Pb1-(a.Math.2/m)Mma.Math.2/m)1-y(Zr1-x-(b.Math.4/n)TixNnb.Math.4/n)yO3, where Mm represents one or more dopings having the respective valence m, Nn represents one or more dopings having the respective valence n and: 0a0.1; 0<b0.2; 0.2x0.8 and 0.4y0.6.

7. A process for producing a ceramic material comprising a hard lead zirconate titanate (PZT) ceramic as claimed in any of the preceding claims, comprising the steps: A) Provision of starting materials Pb, Zr and Ti and doping elements Mn and Cu and optionally additional doping elements, B) Mixing and milling of the starting materials and doping elements to produce a starting mixture, C) Sintering of the starting mixture to the hard PZT ceramic in order to obtain the ceramic material.

8. The process as claimed in the preceding claim, wherein at least one of the doping elements, in particular Cu or, if present, Ag is present in a superstoichiometric proportion relative to the proportion of the doping element in the hard PZT ceramic in the starting mixture.

9. The process as claimed in either claim 7 or 8, wherein step C) is carried out in a sintering atmosphere in which at least one of the doping elements can change its valence.

10. The process as claimed in any of claims 7 to 9, wherein at least part of at least one of the doping elements is reduced to the metal in step C).

11. A ceramic material obtainable by the process as claimed in claim 10, wherein the ceramic material comprises the hard PZT ceramic and metallic precipitates, for example metallic particles, dispersed in the PZT ceramic.

12. The ceramic material as claimed in the preceding claim, wherein the metallic particles comprise at least one of the doping elements in elemental form, in particular elemental copper or elemental silver.

13. A ceramic composition comprising a ceramic component and a metallic component, wherein the ceramic component comprises a hard lead zirconate titanate (PZT) ceramic as claimed in any of claims 1 to 6 and the metallic component comprises a doping element, which is also present in the hard lead zirconate titanate (PZT) ceramic, in a form which has been reduced to the metal.

14. An electroceramic component, in particular a transducer, having a monolithic multilayer structure and comprising a stack of superposed ceramic layers and at least two electrode layers located inbetween, wherein the electrode layers contain elemental copper and the ceramic layers comprise a hard PZT ceramic as claimed in any of claims 1 to 6 or a ceramic material as claimed in claim 11 or a ceramic composition as claimed in claim 13.

15. The electroceramic component as claimed in the preceding claim, wherein a ceramic layer of the stack has subregions adjoining the electrode layers and subregions which are further away and are at a distance of more than 1.5 mm, in particular more than 2 mm or more than 4 mm, away from the electrode layers adjoining the ceramic layer.

16. The electroceramic component as claimed in the preceding claim, wherein the subregions adjoining the electrode layers and the subregions which are further away have Cu contents which differ by not more than 10%.

17. The piezoelectric component as claimed in any of claims 14 to 16, wherein the ceramic layers have a main surface which has a length of from 50 to 150 mm, preferably from 70 to 100 mm, and/or a width of from 4 to 25 mm, preferably from 6 to 18 mm.

18. The piezoelectric component as claimed in the preceding claim, wherein not more than 75%, in particular not more than 60% or not more than 50%, of the main surface of a ceramic layer is covered with an electrode layer.

Description

[0030] The invention will be illustrated below with the aid of figures and working examples, but these are not to be interpreted as restricting the subject matter of the invention. Rather, the invention encompasses each novel feature and each combination of features, which includes, in particular, any combination of features in the claims, even when this feature or this combination is itself not explicitly indicated in the claims or working examples.

[0031] FIG. 1 schematically shows a plan view of a main surface of a ceramic layer KS having an internal copper electrode EL arranged on the ceramic layer. The subregions AT adjoining the electrode layer and subregions ET which are further away are characterized by different patterns.

[0032] FIG. 2 shows photographs of a side face (a) and a main surface (b) of an electroceramic component having a monolithic multilayer structure with internal Cu electrodes and ceramic layers which have been made using a hard PZT ceramic according to the invention.

[0033] FIG. 3 shows photographs of side faces (a) and main surfaces (b) of electroceramic components having a monolithic multilayer structure with internal Cu electrodes and ceramic layers which have been made using a conventional hard PZT ceramic without Cu doping.

[0034] In a working example according to the invention, the PZT ceramic with dopings of 0.0075 atom % of Na on the A sites and 0.054 atom % of Nb, 0.027 atom % of Mn and 0.003 atom % of Cu on the B sites was tested. As comparative example, the corresponding PZT ceramic without Cu doping was used. The PZT ceramics were processed with internal copper electrodes in a monolithic multilayer structure to give electroceramic components. The ceramic layers had a main surface having a length of about 71 mm and a width of about 6 mm. The stack height of the components was about 2.8 mm. The electroceramic components made using the PZT ceramic of the invention displayed particularly advantageous properties in respect of dimensional accuracy and deflection behavior (FIG. 2). In contrast, components made using the conventional ceramic were characterized by considerable distortion both in the stacking direction of the component (FIG. 2a) and transverse to the stacking direction (FIG. 2b).

REFERENCE SYMBOLS

[0035] KS Ceramic layer [0036] EL Internal copper electrode [0037] AT Subregions adjoining electrode layer [0038] ET Subregions further away from electrode layer