Ceramic laminate body, gas sensor element and related manufacturing method

Abstract

A ceramic laminate body, a gas sensor element employing such a ceramic laminate body and related manufacturing method are disclosed as including first and second ceramic sheets, made of material compositions different from each other, and an intermediate bonding layer, bonding the first and second ceramic sheets to each other so as to form a closed hollow space between the first and second ceramic sheets. The intermediate bonding layer has a multilayer structure including first and second unit intermediate layers laminated on each other such that innermost end portions of the first and second unit intermediate layers are displaced from each other to adapt a difference in degreasing contraction rates of associated component parts.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view showing a ceramic laminate body of a first embodiment according to the present invention.

FIG. 2 is a cross sectional view showing a ceramic green sheet, used for the ceramic laminate body shown in FIG. 1, with a status in which a first bonding layer ceramic paste is applied.

FIG. 3 is a cross sectional view showing the ceramic green sheet, used for the ceramic laminate body shown in FIG. 1, with a status in which a second bonding layer paste is formed on the first bonding layer ceramic paste.

FIG. 4 is a cross sectional view showing an unburned ceramic laminate body, employing the ceramic sheet shown in FIG. 3, for use in manufacturing the ceramic laminate body of the first embodiment shown in FIG. 1.

FIG. 5 is a graph showing variations in degreasing contraction factors of the ceramic green sheet and the first and second bonding layer pastes in term of temperatures in the ceramic laminate body of the first embodiment shown in FIG. 1.

FIG. 6 is a cross sectional view showing a ceramic laminate body of a second embodiment according to the present invention.

FIG. 7 is a cross sectional view showing a ceramic laminate body of a third embodiment according to the present invention.

FIG. 8 is a cross sectional view showing a ceramic laminate body of a fourth embodiment according to the present invention.

FIG. 9 is a cross sectional view showing a ceramic laminate body of a fifth embodiment according to the present invention.

FIG. 10 is a cross sectional view showing a gas sensor element of a sixth embodiment according to the present invention.

FIG. 11 is a graph showing measures results on the maximum stresses occurring in the related art ceramic laminate body and the laminate body implementing the present invention.

FIG. 12 is a cross sectional view showing a specimen used as a gas sensor element of a seventh embodiment according to the present invention.

FIG. 13 is a cross sectional view showing another specimen used as a gas sensor element of the related art.

FIG. 14 is a graph showing the relationship between the maximum stress and defective fraction appearing in the gas sensor elements shown in FIGS. 12 and 13.

FIG. 15 is a graph showing the relationship between a displacement value L1 and the maximum stress appearing in the gas sensor elements shown in FIGS. 12 and 13.

FIG. 16 is a cross sectional view showing a ceramic laminate of the related art.

FIG. 17 is an illustrative view for illustrating a stress occurring in a boundary area between a ceramic green sheet and a bonding layer paste forming the ceramic laminate body of the related art shown in FIG. 16.

FIG. 18 is a graph showing a difference in contraction factors of two ceramic green sheets during cooling step.

Claims

1. A ceramic laminate body comprising: a first ceramic sheet;a second ceramic sheet made of material compositions different from those of the first ceramic sheet; andan intermediate bonding layer, bonding the first and second ceramic sheets to each other so as to form a closed hollow space between the first and second ceramic sheets;the intermediate bonding layer has a multilayer structure including first and second unit intermediate layers laminated on each other such that an innermost end portion of one of the first and second unit intermediate layers protrudes inward in the closed hollow space and is displaced from an innermost end portion of the other of the first and second unit intermediate layers.

2. The ceramic laminate body according to claim 1, wherein: the first and second unit intermediate layers, forming the intermediate bonding layer, have a thickness ranging from 5 to 100 μm.

3. The ceramic laminate body according to claim 1, wherein: the innermost end portion of the one of the first and second unit intermediate layers is displaced from the innermost end portion of the other of the first and second unit intermediate layers by a displacement value greater than a thickness of the one of the first and second unit intermediate layers.

4. The ceramic laminate body according to claim 1, wherein: the one of the first and second unit intermediate layers is made of alumina in major proportions and the other of the first and second unit intermediate layers is made of zirconia in major proportions.

5. The ceramic laminate body according to claim 1, wherein: the first and second unit intermediate layers have inward end portions, exposed to the closed hollow space, which have substantially arc-shaped configurations in cross section, respectively.

6. The ceramic laminate body according to claim 1, wherein: the first and second unit intermediate layers have different degreasing contraction factors.

7. The ceramic laminate body according to claim 6, wherein: the first unit intermediate layer comprises a hardened adhesive paste and the second unit intermediate layer comprises a hardened ceramic paste.

8. The ceramic laminate body according to claim 1, wherein: the intermediate bonding layer further includes a third unit intermediate layer interposed between the second unit intermediate layer and the second ceramic sheet.

9. The ceramic laminate body according to claim 8, wherein: the third unit intermediate layer has an innermost end portion protruding further inward to the closed hollow space than the innermost end portion of the second unit intermediate layer by a displacement value greater than a thickness of the third unit intermediate layer.

10. The ceramic laminate body according to claim 8, wherein: the third unit intermediate layer has an innermost end portion exposed to the closed hollow space and is displaced outward from the innermost end portion of the second unit intermediate layer by a displacement value greater than a thickness of the third unit intermediate layer.

11. The ceramic laminate body according to claim 5, wherein: the arc-shaped configurations of the first and second unit intermediate layers are aligned on the same orientations.

12. The ceramic laminate body according to claim 5, wherein: the arc-shaped configurations of the first and second unit intermediate layers are aligned on the opposite orientations.

13. The ceramic laminate body according to claim 1, wherein: the second ceramic sheet has a recessed portion to define a part of the closed hollow space.

14. The ceramic laminate body according to claim 1, wherein: the innermost end portions of the first and second unit intermediate layers are displaced from each other by a displacement value expressed by t≦L1 where “t” represents a thickness of one of the first and second unit intermediate layers and “L1” represents the displacement value between the innermost end portions of the first and second unit intermediate layers.

15. A gas sensor element comprising: a ceramic laminate body including a first ceramic sheet, a second ceramic sheet made of material compositions different from those of the first ceramic sheet, and an intermediate bonding layer, bonding the first and second ceramic sheets to each other so as to form a closed hollow space between the first and second ceramic sheets, which has a multilayer structure including first and second unit intermediate layers laminated on each other such that an innermost end portion of one of the first and second unit intermediate layers protrudes inward in the closed hollow space and is displaced from an innermost end portion of the other of the first and second unit intermediate layers;a reference gas detecting electrode formed on one surface of the first ceramic sheet in face-to-face relation with the closed hollow space;a measuring gas detecting electrode formed on the other surface of the first ceramic sheet and exposed in a measuring gas chamber;a diffusion resistance layer stacked on the other surface of the first ceramic sheet so as to define the measuring gas chamber in an area around the measuring gas detecting electrode and operative to permeate measuring gas to the measuring gas chamber; anda shielding layer laminated on the diffusion resistance layer.

16. A method of manufacturing a ceramic laminate body, the method comprising the steps of: preparing a first green ceramic sheet;preparing a second green ceramic sheet made of material compositions different from those of the first ceramic sheet;forming first and second bonding layer pastes, having different degreasing contraction factors, on at least one of the first and second ceramic sheets to form an intermediate bonding layer in a multilayer structure;stacking the first and second ceramic green sheets via the intermediate bonding layer so as to form a closed hollow space for thereby providing an unburned laminate body; andfiring the unburned laminate body to form the ceramic laminate body.

17. The method of manufacturing the ceramic laminate body according to claim 16, wherein: the first bonding layer paste comprises an adhesive paste and the second bonding layer paste comprises a ceramic paste having a degreasing contraction factor between those of the first bonding layer and one of the first and second ceramic green sheets.

18. The method of manufacturing the ceramic laminate body according to claim 16, wherein: the first and second bonding layer pastes are formed in a pattern such that an innermost end portion of one of the first and second bonding layer pastes protrudes inward in the closed hollow space and is displaced from an innermost end portion of the other of the first and second bonding layer pastes.

19. The method of manufacturing the ceramic laminate body according to claim 16, wherein: the ceramic laminate body forms a part of a gas sensor element of a stack type for detecting a specified gas concentration in measuring gases.

20. The method of manufacturing the ceramic laminate body according to claim 16, wherein: the first and second bonding layer pastes, forming the intermediate bonding layer, have a thickness ranging from 5 to 100 μm in hardened states.

21. The method of manufacturing the ceramic laminate body according to claim 16, wherein: the innermost end portion of the one of the first and second bonding layer pastes is displaced from the innermost end portion of the other of the first and second bonding layer pastes by a displacement value greater than a thickness of the one of the first and second bonding layer pastes.

22. The method of manufacturing the ceramic laminate body according to claim 16, wherein: the one of the first and second bonding layer pastes is made of alumina in major proportions and the other of the first and second bonding layer pastes is made of zirconia in major proportions.

23. The method of manufacturing the ceramic laminate body according to claim 16, wherein: the first and second bonding layer pastes have inward end portions, exposed to the closed hollow space, which have substantially arc-shaped configurations in cross section, respectively.

24. The method of manufacturing the ceramic laminate body according to claim 16, further comprising the step of: forming a third bonding layer paste on at least the other one of the first and second ceramic sheets.

25. The method of manufacturing the ceramic laminate body according to claim 24, wherein: the third bonding layer paste has an innermost end portion protruding further inward to the closed hollow space than the innermost end portion of the second third bonding layer paste by a displacement value greater than a thickness of the third bonding layer paste.

26. The method of manufacturing the ceramic laminate body according to claim 24, wherein: the third bonding layer paste has an innermost end portion exposed to the closed hollow space and is displaced outward from the innermost end portion of the second bonding layer paste by a displacement value greater than a thickness of the third bonding layer paste.

27. The method of manufacturing the ceramic laminate body according to claim 23, wherein: the arc-shaped configurations of the first and second bonding layer pastes are aligned on the same orientations.

28. The method of manufacturing the ceramic laminate body according to claim 23, wherein: the arc-shaped configurations of the first and second bonding layer pastes are aligned on the opposite orientations.

29. The method of manufacturing the ceramic laminate body according to claim 16, wherein: the second ceramic sheet has a recessed portion to define a part of the closed hollow space.

30. The method of manufacturing the ceramic laminate body according to claim 18, wherein: the innermost end portions of the first and second bonding layer pastes are displaced from each other by a displacement value expressed by t≦L1 where “t” represents a thickness of one of the first and second bonding layer pastes and “L1” represents the displacement value between the innermost end portions of the first and second bonding layer pastes.