Ceramic material, component, and method for producing the component

Abstract

A ceramic material, a component, and a method for producing a component are disclosed. In an embodiment a ceramic material includes a structure based on a system selected from the group consisting of NiCoMnO, NiMnO and CoMnO, and at least one dopant selected from lanthanides, wherein the ceramic material has a negative temperature coefficient of an electrical resistance.

Claims

1. A ceramic material comprising: a structure based on a system selected from the group consisting of NiCoMnO, NiMnO, and CoMnO; and at least one dopant selected from lanthanides, wherein the dopant is selected from the group consisting of Pr, Nd, and combinations thereof, and wherein the ceramic material has a negative temperature coefficient of an electrical resistance.

2. The ceramic material according to claim 1, wherein the dopant is contained in the ceramic material in an amount of up to and including 10 mol %.

3. The ceramic material according to claim 1, wherein the system further contains at least one element selected from Al, Fe, Cu, Zn, Ca, Zr, Ti, Mg, Sr and combinations thereof.

4. The ceramic material according to claim 1, wherein the ceramic material has a spinel structure.

5. The ceramic material according to claim 4, wherein the spinel structure has the general formula AB.sub.2O.sub.4, wherein A is selected from the group consisting of Ni, Co, Mn, Mg, Sr, Zn, Ca, Zr, Cu and combinations thereof, wherein B is selected from the group consisting of Mn, Co, Al, Fe, Ti and combinations thereof, and wherein A comprises at least Ni and B comprises at least Mn, or A comprises at least Ni and B comprises at least Mn and Co, or A comprises at least Mn or Co and B comprises at least Co or Mn.

6. The ceramic material according to claim 5, wherein the dopant is disposed at a B position of the spinel structure.

7. The ceramic material according to claim 5, wherein the spinel structure is selected from the group consisting of NiMn.sub.2O.sub.4, Ni.sup.2+Mn.sup.3+Co.sup.3+O.sub.4, MnCo.sub.2O.sub.4, and CoMn.sub.2O.sub.4.

8. A component comprising: a ceramic base element comprising a ceramic material according to claim 1; and at least two electrodes disposed on the ceramic base element.

9. The component according to claim 8, wherein the component is a temperature sensor.

10. The component according to claim 8, wherein the ceramic base element has a volume selected from a range of 0.03 cm.sup.3 inclusive to 0.23 cm.sup.3 inclusive.

11. The component according to claim 8, wherein the ceramic base element has a resistance R.sub.25 selected from a range of 2000 to 3000 and a B value selected from a range of 3500 K to 4300 K.

12. The component according to claim 8, further comprising an encapsulation, wherein the encapsulation comprises glass or a polymer.

13. A method for producing the component according to claim 8, the method comprising: producing a powder containing starting materials of the ceramic material; producing a film from the powder; producing substrates containing the ceramic material from the film; and singulating the substrates.

14. The method according to claim 13, further comprising adding further starting materials of the at least one dopant in form of oxides, hydroxides, carbonates, nitrates, sulfates and/or oxalates to the starting materials in order to produce the powder.

15. A ceramic material comprising: a structure based on a system selected from the group consisting of NiCoMnO, NiMnO, and CoMnO; and at least one dopant selected from lanthanides, wherein the ceramic material has a negative temperature coefficient of an electrical resistance, wherein the dopant is contained in the ceramic material in an amount of up to and including 10 mol %, and wherein the ceramic material has a spinel structure of the general formula AB.sub.2O.sub.4, where: A is selected from the group consisting of Ni, Co, Mn, Mg, Sr, Zn, Ca, Zr, Cu and combinations thereof, B is selected from the group consisting of Mn, Co, Al, Fe, Ti and combinations thereof, and A comprises at least Ni and B comprises at least Mn, or A comprises at least Ni and B comprises at least Mn and Co, or A comprises at least Mn or Co and B comprises at least Co or Mn, wherein the dopant is disposed at a B position of the spinel structure.

16. A component comprising: a ceramic base element comprising a ceramic material, the ceramic material comprising: a structure based on a system selected from the group consisting of NiCoMnO, NiMnO, and CoMnO; and at least one dopant selected from lanthanides, wherein the ceramic material has a negative temperature coefficient of an electrical resistance; and at least two electrodes disposed on the ceramic base element, wherein the ceramic base element has a volume selected from a range of 0.03 cm.sup.3 inclusive to 0.23 cm.sup.3 inclusive, or wherein the ceramic base element has a resistance R.sub.25 selected from a range of 2000 to 3000 and a B value selected from a range of 3500 K to 4300 K.

17. The component according to claim 16, wherein the system further contains at least one element selected from Al, Fe, Cu, Ti, Mg, and combinations thereof.

18. The component according to claim 16, wherein the ceramic material has a spinel structure.

19. The component according to claim 18, wherein the spinel structure has the general formula AB.sub.2O.sub.4, wherein A is selected from the group consisting of Ni, Co, Mn, Mg, Sr, Zn, Ca, Zr, Cu and combinations thereof, wherein B is selected from the group consisting of Mn, Co, Al, Fe, Ti and combinations thereof, and wherein A comprises at least Ni and B comprises at least Mn, or A comprises at least Ni and B comprises at least Mn and Co, or A comprises at least Mn or Co and B comprises at least Co or Mn.

20. The component according to claim 19, wherein the spinel structure is selected from the group consisting of NiMn.sub.2O.sub.4, Ni.sup.2+Mn.sup.3+Co.sup.3+O.sub.4, MnCo.sub.2O.sub.4, and CoMn.sub.2O.sub.4.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the ceramic material and component described here will be explained in greater detail by means of exemplary embodiments and accompanying figures.

(2) FIG. 1 shows the relationship between resistivity p and the B value by means of exemplary embodiments;

(3) FIGS. 2A and 2B show the effect of the amount of dopant added 1 in accordance with the basic formulation of the ceramic material on the B value and the resistivity p by means of exemplary embodiments;

(4) FIGS. 3A to 3C show the drift behavior of the ceramic material under various conditions;

(5) FIG. 4A shows a schematic side view of a conventional component; and

(6) FIG. 4B shows an exemplary embodiment of a component.

(7) Elements in the figures that are identical, similar, or have the same effect are indicated with the same reference numbers. The figures and the size relationships among the elements shown in the figures are not to be considered true to scale. Rather, the size of individual elements may be exaggerated in order to make them clearer and/or easier to understand.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(8) FIG. 1 shows the relationship between the resistivity p and the B value for conventional undoped NTC ceramics (P) based on the systems NiMnCoO.sub.4 and NiMn.sub.2O.sub.4 and for the exemplary embodiments of doped ceramic materials Co.sub.1.5-0.5aMn.sub.1.5-0.5aPr.sub.aO.sub.4, Co.sub.1.8-0.5aMn.sub.1.2-0.5aPr.sub.aO.sub.4, and Ni.sub.0.97-0.33aMn.sub.1.2-0.33aFe.sub.0.82-0.33aPr.sub.aO.sub.4, where 0<a0.3 (E). The x axis shows the B value in K, and the y axis shows the resistivity in cm. The diamonds P indicate the values for conventional NTC ceramics, and the squares E indicate the values for the exemplary embodiments of the ceramic material.

(9) It can be seen from FIG. 1 that for the ceramic materials doped with a lanthanide (E), resistivity values of 200cm to 500cm can be set over a B value range of 3500 K to 4300 K. In the same B value range, the resistivity values p for conventional NTC ceramics (P) are between 500cm and 20000cm.

(10) The low resistivity values of the lanthanide-doped ceramic materials are advantageous in that in contrast to the NTC ceramic compositions of prior art, substantially smaller component shapes can be realized with the same real resistance values. Because of the resulting reduction in component sizes, more NTC ceramic bodies comprising the ceramic material can be produced from the same basic amount of ceramic material. This provides a cost advantage and makes up for higher raw material costs.

(11) FIGS. 2A and 2B show the effect of the amount of dopant added 1, depending on the basic formulation of the ceramic material, on the B value (FIG. 2A) and the value (FIG. 2B). The x axis shows the respective amount of 1 added in mol %. The y axis of FIG. 2A represents the B value in K, and the y axis of FIG. 2B shows the resistivity p in Scm.

(12) The two basic formulations are indicated by squares E.sub.1 (basic formulation 1) and diamonds E.sub.2 (basic formulation 2) respectively. The term basic formulation is to be understood as referring to the respective composition of the ceramic material to which different amounts of the dopant 1 are added. Basic formulation E.sub.1 is Co.sub.1.8-0.5aMn.sub.1.5-0.5aPr.sub.aO.sub.4, where 0<a0.3, and basic formulation E.sub.2 is Co.sub.1.8-0.5aMn.sub.1.2-0.5aPr.sub.aO.sub.4, where 0<a0.3.

(13) It can be clearly seen from FIGS. 2A and 2B that the B values can be modified by selecting the basic formulation E.sub.1 or E.sub.2 to which the dopants are added (FIG. 2A), wherein at the same time, the resistivity remains independent of the basic formulation (FIG. 2B).

(14) FIGS. 3A to 3C show the drift behavior of the ceramic material by means of an exemplary embodiment under different conditions. The drift behavior is determined by means of glass-encapsulated NTC temperature detectors containing the lanthanide-doped ceramic material. The lanthanide-doped ceramic material has a structure based on the system NiCoMnO, NiMnO, or CoMnO. The systems can optionally also comprise Al, Fe, Cu, Zn, Ca, Zr, Ti, Mg, Sr and combinations thereof, and the system has a spinel structure. The ceramic material has a dopant concentration of up to 10 mol %. The dopant is preferably Pr, Nd, or combinations thereof. For example, it can be Co.sub.1.5-0.5aMn.sub.1.5-0.5aPr.sub.aO.sub.4, Co.sub.1.8-0.5aMn.sub.1.2-0.5aPr.sub.aO.sub.4, or Ni.sub.0.97-0.33aMn.sub.1.21-0.33aFe.sub.0.82-0.33aPr.sub.aO.sub.4, where 0<a0.3 in each case.

(15) FIG. 3A shows the drift behavior dR/R in % relative to the time t in hours h. T.sub.1 shows the behavior of the ceramic material under a first temperature storage condition in dry heat at 155 C., and T.sub.2 shows the behavior at a second temperature storage condition in dry heat at 300 C. Under both temperature storage conditions T.sub.1 and T.sub.2, the ceramic material shows a quite minimal drift behavior of less than 0.5%, even after 1000 hours.

(16) FIG. 3B shows the drift behavior dR/R in % with a rapid temperature change. The x axis in FIG. 3B shows the number of cycles Z of the temperature change. TW.sub.1 shows the behavior with a rapid temperature change (first temperature change condition) from 55 C. to 155 C., and TW.sub.2 shows the behavior with a rapid temperature change (second temperature change condition) from 55 C. to 200 C. Under both condition TW.sub.1 and condition TW.sub.2, no change in resistance R can be seen.

(17) FIG. 3C shows the effect of storage in moist heat on the drift behavior dR/R. This is again indicated in % on the y axis. The x axis shows the number of days d. Storage is carried out at a temperature of 85 C. and at 85% relative humidity. Under these conditions as well, the observed drift behavior is below 0.5%.

(18) FIG. 4A shows a schematic side view of a conventional component compared to an exemplary embodiment of a component shown in FIG. 4B. Both components comprise electrodes 10. The conventional component I further comprises the ceramic base element 20, which has a volume of 1.8 to 3.4 cm.sup.3. By contrast, the ceramic base element 30 of the exemplary embodiment of the component II has a volume of 0.03 to 0.23 cm.sup.3. Both components have a resistance R.sub.25 of 2200 and a B value of 3500 to 4300 K. The component I shows an resistivity p of 1500 to 3000cm, and that of component II is 200 to 500cm. Components I and II can further comprise encapsulations, e.g., of glass or a polymer (not shown here).

(19) The ceramic base element 30 of the component II comprises a lanthanide-doped ceramic material having a structure based on the system NiCoMnO, NiMnO, or CoMnO. The systems can optionally also comprise Al, Fe, Cu, Zn, Ca, Zr, Ti, Mg, Sr and combinations thereof, and the system has a spinel structure. The ceramic material has a dopant concentration of up to 10 mol %. The dopant is preferably Pr, Nd or combinations thereof. For example, the ceramic material is Co.sub.1.5-0.5aMn.sub.1.5-0.5aPr.sub.aO.sub.4, Co.sub.1.8-0.5aMn.sub.1.2-0.5aPr.sub.aO.sub.4, or Ni.sub.0.97-0.33aMn.sub.1.21-0.33aFe.sub.0.82-0.33aPr.sub.aO.sub.4, with 0<a0.3 in each case.

(20) It can thus be shown that by selecting the ceramic material, the component size can be dramatically reduced, and at the same time, high B values combined with low resistivity values can be realized.

(21) The invention is not limited to the description by means of the exemplary embodiments. Rather, the invention comprises each new feature and each combination of features that in particular contain(s) each combination of features in the patent claims, even if this feature or this combination is/are not explicitly mentioned in the patent claims or examples.