WO2016129578A1

WO2016129578A1 - Gas sensor

Info

Publication number: WO2016129578A1
Application number: PCT/JP2016/053752
Authority: WO
Inventors: 重和日高
Original assignee: 株式会社デンソー
Priority date: 2015-02-12
Filing date: 2016-02-09
Publication date: 2016-08-18

Abstract

　Provided is a gas sensor in which a facing plate can be made less susceptible to cracking, and the temperature distribution (temperature difference) in a gas chamber to be measured can be reduced. This gas sensor 1 includes: a solid electrolyte substrate 2 that has oxygen ion conductivity; a ceramic facing plate 3 that is disposed facing a first surface 201 of the solid electrolyte substrate 2; a ceramic first spacer 51 that is interposed between the facing plate 3 and the solid electrolyte substrate 2; a ceramic heater substrate 4 that is disposed facing a second surface 202 of the solid electrolyte substrate 2; and a ceramic second spacer 52 that is interposed between the heater substrate 4 and the solid electrolyte substrate 2. The sintered density of an inner section 31 of the facing plate 3 in contact with a gas chamber 101 to be measured is 0.8-5.0% less than the sintered density of an outer section 32 of the facing plate 3 in contact with the first spacer 51.

Description

Gas sensor

Cross-reference of related applications

This application is based on Japanese Application No. 2015-25776 filed on February 12, 2015 and Japanese Application No. 2015-197908 filed on October 5, 2015, the contents of which are incorporated herein by reference. To do.

The present disclosure relates to a gas sensor formed by laminating a counter plate and a heater substrate on a solid electrolyte substrate.

For example, a gas sensor that detects the concentration of a specific gas component such as NOx has a solid electrolyte substrate having electrodes on its surface, a counter plate and a first spacer that form a gas chamber to be measured, and a first gas chamber that forms a reference gas chamber. The two spacers and the heater substrate for heating the solid electrolyte substrate are laminated to form. The gas chamber to be measured is formed between the solid electrolyte substrate and the counter plate and surrounded by the first spacer, and the reference gas chamber is surrounded by the second spacer between the solid electrolyte substrate and the heater substrate. It is formed.

Further, when the solid electrolyte substrate is heated by the heater substrate, the temperature of the gas chamber to be measured becomes higher as the temperature is closer to the heater substrate. This temperature distribution in the gas chamber to be measured affects the detection accuracy of the concentration of the specific gas component. Therefore, a device has been devised to mitigate the influence of this temperature distribution.

For example, Patent Document 1 describes a gas sensor formed by laminating a heater on a laminate of solid electrolyte layers provided with a measurement electrode and a reference electrode. Further, the reference electrode located closer to the heater than the measurement electrode is covered with a reference gas introduction layer that is a porous body. This makes it difficult for heat from the heater to be transmitted to the reference electrode, reduces the temperature difference between the reference electrode and the measurement electrode, and reduces variations in electromotive force generated between the reference electrode and the measurement electrode.

JP 2012-211183 A

By the way, when the gas sensor is used, heat from the heater substrate is transmitted to the second spacer, the solid electrolyte substrate, and the first spacer by heat conduction. In the counter plate, the portion overlapping the first spacer is more easily heated than the portion in contact with the gas chamber to be measured. In addition, the portion of the counter plate that contacts the gas chamber to be measured is easily cooled by heat radiation to the outside. Therefore, the portion of the counter plate that contacts the gas chamber to be measured is pulled by the portion of the counter plate that overlaps the first spacer, and tensile stress acts on the portion of the counter plate that contacts the gas chamber to be measured. And depending on the case, there exists a possibility that a crack may arise in the boundary position of both. Even Patent Document 1 cannot solve this cracking problem.

In order to prevent the counter plate from cracking, it is conceivable to increase the thickness of the counter plate. However, in this case, another problem arises in that the heat from the heater is taken away by the counter plate, and the activation time of the gas sensor becomes long.

The present disclosure has been made in view of such a background, and is obtained by providing a gas sensor that can make a counter plate less likely to be cracked and can reduce a temperature distribution (temperature difference) in a gas chamber to be measured. It is what was done.

One aspect of the present disclosure includes a solid electrolyte substrate having oxygen ion conductivity, a ceramic counter plate disposed to face the first surface of the solid electrolyte substrate, the counter plate, and the solid electrolyte substrate. Between the counter plate and the solid electrolyte substrate, a ceramic first spacer that forms a gas chamber to be measured and a heat generation layer that generates heat when energized are sandwiched between the counter plate and the solid electrolyte substrate. A ceramic heater substrate disposed opposite to the second surface of the solid electrolyte substrate, and sandwiched between the heater substrate and the solid electrolyte substrate; and between the heater substrate and the solid electrolyte substrate. A ceramic-made second spacer that forms a reference gas chamber for allowing a reference gas to flow in between, and a sintered dense portion of an inner portion including a region in contact with the gas chamber to be measured in the counter plate Is from 0.8 to 5.0% lower than the sintered density of the outer portion including a region in contact with the first spacer, in the gas sensor.

The inner portion can be the entire region (portion) in contact with the gas chamber to be measured in the counter plate, or can be a part of the region in contact with the gas chamber to be measured in the counter plate. Further, the inner portion can be the entire region in contact with the gas chamber to be measured in the counter plate and a part of the region in contact with the first spacer in the counter plate (portion overlapping the first spacer).

Cross-sectional explanatory drawing which shows the sensor element concerning embodiment. FIG. 2 is a diagram illustrating the sensor element according to the embodiment, and is a cross-sectional explanatory view taken along line II-II in FIG. 1. FIG. 3 is a diagram illustrating the sensor element according to the embodiment, and is a cross-sectional explanatory view taken along line III-III in FIG. 1. Explanatory drawing which shows the sensor element concerning the embodiment seen from the direction of the arrow X of FIG. Cross-sectional explanatory drawing which shows the state which pinches | interposes the laminated body of the sensor element concerning 1st Embodiment between a 1st type | mold and a 2nd type | mold, and sinters. FIG. 4 is a diagram illustrating another sensor element according to the embodiment, and is an explanatory diagram corresponding to a cross section taken along line II-II in FIG. FIG. 4 is a diagram illustrating another sensor element according to the embodiment, and is an explanatory diagram corresponding to a cross section taken along line II-II in FIG. FIG. 4 is a diagram illustrating another sensor element according to the embodiment, and is an explanatory diagram corresponding to a cross section taken along line II-II in FIG.

Preferred embodiments of the above-described gas sensor will be described with reference to the drawings.

As shown in FIGS. 1 to 3, the gas sensor 1 of this embodiment includes a solid electrolyte substrate 2 having oxygen ion conductivity, a ceramic counter plate 3, a ceramic first spacer 51, a ceramic heater substrate 4, and A ceramic second spacer 52 is provided.

The counter plate 3 is disposed to face the first surface 201 of the solid electrolyte substrate 2. The first spacer 51 is sandwiched between the opposing plate 3 and the solid electrolyte substrate 2, and the measured gas chamber 101 for allowing the measured gas G to flow between the opposing plate 3 and the solid electrolyte substrate 2. Is formed. The heater substrate 4 has a heat generating layer 41 that generates heat when energized, and is disposed to face the second surface 202 of the solid electrolyte substrate 2. The second spacer 52 is sandwiched between the heater substrate 4 and the solid electrolyte substrate 2, and forms a reference gas chamber 102 for allowing the reference gas A to flow between the heater substrate 4 and the solid electrolyte substrate 2. To do. As shown in FIGS. 1, 2, and 4, the sintering density of the inner portion 31 located in the region in contact with the gas chamber 101 to be measured (that is, the portion adjacent to the gas chamber 101 to be measured) in the counter plate 3 is The sintered density of the outer portion 32 located in the region in contact with the first spacer 51 (that is, the portion overlapping the first spacer 51) is 0.8 to 5.0% lower. In the present disclosure, the expression “numerical value to numerical value” includes a numerical value at the boundary.

Hereinafter, the gas sensor 1 of the present embodiment will be described in detail with reference to FIGS.

The solid electrolyte substrate 2, the counter plate 3, the first spacer 51, the heater substrate 4, and the second spacer 52 constitute the sensor element 10 of the gas sensor 1.

The sensor element 10 is held in a housing via an insulator, and a cover that covers the sensor element 10 is attached to the housing. And the gas sensor 1 comprised using the sensor element 10, an insulator, a housing, and a cover is arrange | positioned at the exhaust pipe of an internal combustion engine. The gas sensor 1 is used to detect the concentration of NOx (that is, nitrogen oxide) as a specific gas component in the exhaust gas using the exhaust gas passing through the exhaust pipe as the measurement gas G.

As shown in FIGS. 1 to 3, the first surface 201 of the solid electrolyte substrate 2 has a pump electrode 21 used for adjusting the oxygen concentration in the gas G to be measured, and the oxygen concentration is adjusted in the pump electrode 21. In order to detect the NOx concentration in the measurement gas G after the oxygen concentration is adjusted in the monitor electrode 22 and the pump electrode 21 used for measuring the residual oxygen concentration in the measurement gas G after A sensor electrode 23 to be used is provided. On the second surface 202 of the solid electrolyte substrate 2, a reference electrode 24 that is exposed to the reference gas A that is the atmosphere is provided at a position opposite to the position where the pump electrode 21, the monitor electrode 22, and the sensor electrode 23 are provided. ing. The reference electrode 24 can be individually provided on the opposite side of the position where the pump electrode 21, the monitor electrode 22, and the sensor electrode 23 are provided.

The pump electrode 21 and the monitor electrode 22 are made of a material showing activity against oxygen, and the sensor electrode 23 is made of a material showing activity against oxygen and NOx.

As shown in FIGS. 1 and 2, between the pump electrode 21 and the reference electrode 24, the voltage application means 61 uses the solid electrolyte substrate 2 to make the oxygen concentration in the measurement gas G constant. A variable voltage is applied. A predetermined voltage is applied between the monitor electrode 22 and the reference electrode 24 and between the sensor electrode 23 and the reference electrode 24 via the solid electrolyte substrate 2 to show the limiting current characteristics.

A pump cell is formed by the pump electrode 21, the reference electrode 24, and the solid electrolyte substrate 2 sandwiched between them. A monitor cell is formed by the monitor electrode 22, the reference electrode 24, and the solid electrolyte substrate 2 sandwiched between them. A sensor cell is formed by the sensor electrode 23, the reference electrode 24, and the solid electrolyte substrate 2 sandwiched between them.

In the monitor cell, the oxygen ion current flowing between the monitor electrode 22 and the reference electrode 24 via the solid electrolyte substrate 2 is measured by the current detection means 62, whereby the residual oxygen concentration in the gas G to be measured is obtained. . In the sensor cell, the current detection means 63 measures the oxygen ion current flowing between the sensor electrode 23 and the reference electrode 24 via the solid electrolyte substrate 2, so that the NOx concentration and the residual oxygen concentration in the measurement gas G are measured. The sum of is required. Then, the NOx concentration in the measurement gas G is obtained by subtracting the oxygen ion current of the monitor cell from the oxygen ion current of the sensor cell.

As shown in FIGS. 1 and 3, a gas introduction port 511 for introducing the measurement gas G into the measurement gas chamber 101 is provided at the tip of the sensor element 10. The gas inlet 511 is provided at the tip of the first spacer 51, and the porous body 512 as a diffusion resistor when the gas G to be measured is introduced into the gas chamber 101 to be measured is provided in the gas inlet 511. Is arranged.

The gas G to be measured flows in the gas chamber 101 to be measured from the distal end side where the gas inlet 511 is provided to the proximal end side. The pump electrode 21 is arranged at a position close to the gas inlet 511, and the monitor electrode 22 and the sensor electrode 23 are located downstream of the pump electrode 21 in the flow of the gas G to be measured in the gas chamber 101 to be measured. They are arranged side by side in the horizontal direction B.

The reference gas A is introduced into the reference gas chamber 102 from the base end side of the second spacer 52. The heater substrate 4 wraps in all directions a heat generating layer 41 that generates Joule heat when energized.

The solid electrolyte substrate 2 is made of yttria-stabilized zirconia, and the counter plate 3, the first spacer 51, the second spacer 52, and the heater substrate 4 are made of alumina (that is, aluminum oxide) that exhibits insulation properties. Yes. In addition to alumina, the insulating material constituting the counter plate 3 and the like can be aluminum nitride, silicon nitride, cordierite, mullite, steatite, forsterite, or the like.

The counter plate 3, the heater substrate 4, the first spacer 51, and the second spacer 52 are sintered bodies obtained by sintering (firing) a material having ceramic particles, a solvent, and a binder at a predetermined temperature. In the sintered body, the solvent and the binder are removed, the volume shrinks, and the ceramic particles are bonded together. The sintering density of the outer portion 32, the heater substrate 4, the first spacer 51, and the second spacer 52 in the counter plate 3 is in the range of 95 to 100%. Thereby, the intensity | strength of the outer part 32, the heater board | substrate 4, the 1st spacer 51, and the 2nd spacer 52 can be kept appropriate.

Here, the case where the sintered density is 100% means a state in which the whole amount of the solvent and the binder is removed, and only the ceramic particles that are bonded to each other are left, and the entire ceramic particles are completely contracted. For example, the case where the sintered density is 95% means a case where the bulk density is 5% smaller than the bulk density (kg / m3) when the sintered density is 100%.

When the sensor element 10 is manufactured, as shown in FIG. 5, the solid electrolyte sheet, the counter plate 3, the heater substrate 4, the first spacer 51, and the second spacer 52 that constitute the solid electrolyte substrate 2 are formed. A laminated body (that is, the sensor element 10) is formed by laminating ceramic sheets. Moreover, the 1st type | mold 71 and the 2nd type | mold 72 for applying a pressure to a laminated body are used. A concave portion 711 for reducing pressure is formed in a portion of the first mold 71 that faces the inner portion 31 of the counter plate 3.

And a laminated body is inserted | pinched between the 1st type | mold 71 and the 2nd type | mold 72, a pressure is applied to a laminated body, a laminated body is heated in the state which applied this pressure, and a laminated body is sintered. At this time, the pressure acting on the inner portion 31 of the counter plate 3 facing the concave portion 711 of the first mold 71 is smaller than the pressure acting on the outer portion 32 of the counter plate 3. As a result, the interparticle distance of the ceramic particles constituting the inner portion 31 becomes larger than the interparticle distance of the ceramic particles constituting the outer portion 32. That is, by making the pressure applied to the inner part smaller than the pressure applied to the outer part at the time of sintering, the degree of close contact between the ceramic particles is relaxed, and the sintering density of the inner part is made smaller than the sintering density of the outer part. Can be lowered.

It should be noted that a sheet 73 that is evaporated and completely removed when the laminate is sintered is disposed in the space in which the gas chamber 101 to be measured and the space in which the reference gas chamber 102 is formed.

Next, when the laminate is heated to evaporate the solvent and the binder, the state in which the interparticle distance of the ceramic particles constituting the inner portion 31 is larger than the interparticle distance of the ceramic particles constituting the outer portion 32 is maintained. The Thereby, when the laminate is sintered, a state is formed in which the sintered density of the inner portion 31 in the opposing plate 3 is 0.8 to 5.0% lower than the sintered density of the outer portion 32 in the opposing plate 3. Is done. Thus, the inner portion 31 forms a portion having a coarse sintered density because the shrinkage rate during sintering is smaller than that of the outer portion 32.

As shown in FIG. 4, the inner portion 31 of the counter plate 3 of the present embodiment is a portion in contact with the measured gas chamber 101. Further, the inner portion 31 of the counter plate 3 is the entire portion of the counter plate 3 that forms the measured gas chamber 101, in other words, the entire portion that does not overlap the first spacer 51. On the other hand, the outer portion 32 of the counter plate 3 of the present embodiment is a portion in contact with the first spacer 51. The outer portion 32 of the counter plate 3 is the entire portion of the counter plate 3 that overlaps the first spacer 51, in other words, the entire portion of the counter plate 3 that does not form the measured gas chamber 101. The outer portion 32 is formed so as to surround the entire circumference of the inner portion 31.

In the counter plate 3 of this embodiment, the width in the horizontal direction B of the gas chamber 101 to be measured and the width in the horizontal direction B of the inner portion 31 are the same.

Here, in the sensor element 10, the direction in which the distal end side and the proximal end side are located is defined as the longitudinal direction L, and the direction in which the solid electrolyte substrate 2, the counter plate 3, the first spacer 51, the heater substrate 4, and the second spacer 52 overlap each other. The laminating direction T is set, and the lateral direction B is a direction orthogonal to the longitudinal direction L and the laminating direction T.

The inner portion 31 of the counter plate 3 can be configured as follows.

As shown in FIG. 6, the inner portion 31 is a part of a region in contact with the measured gas chamber 101 in the opposing plate 3, and the outer portion 32 is a remaining portion of the region in contact with the measured gas chamber 101 in the opposing plate 3; It can be a region in contact with the first spacer 51 in the counter plate 3. In this case, when the width of the gas chamber 101 to be measured in the horizontal direction B is W, the width W1 of the inner portion 31 in the horizontal direction B is in the range of 0.8 W to less than 1.0 W.

As shown in FIG. 7, the inner portion 31 is the entire region in contact with the gas chamber 101 to be measured and a part of the region in contact with the first spacer 51 in the counter plate 3, and the outer portion 32 is in the counter plate. 3, the remaining part of the region in contact with the first spacer 51. In this case, when the width of the gas chamber 101 to be measured in the horizontal direction B is W, the width W1 of the inner portion 31 in the horizontal direction B is in the range of more than 1.0 W and not more than 1.5 W.

In the case of FIG. 7, as shown in FIG. 8, the counter plate 3 includes an inner portion 31 A located on the inner side and an outer portion 32 A that is located outside the inner portion 31 A and has a smaller thickness than the inner portion 31 A. And can be formed. The outer portion 32 A has a reduced thickness so that the surface facing the first spacer 51 approaches the outer surface 301 of the facing plate 3. Further, the corner portion on the side facing the first spacer 51 in the inner portion 31A is formed on the tapered surface 311 and the corner portion on the side facing the inner portion 31A in the first spacer 51 is formed with the tapered surface 311. The taper surfaces 513 can be opposed to each other. In this case, the interface between the counter plate 3 and the first spacer 51 can be widened to increase the ratio of the inner portion 31A having a coarse sintered density.

The gas sensor 1 of this embodiment is designed to intentionally generate stress on the counter plate 3 by partially changing the sintering density (firing density) of the counter plate 3.

Specifically, the opposing plate 3 is provided with an inner portion 31 and an outer portion 32, and the sintering density of the inner portion 31 is 0.8 to 5.0% lower than the sintering density of the outer portion 32. . When the sintered density of the inner portion 31 is lower than the sintered density of the outer portion 32, the sensor element 10 can be manufactured in a state where compressive stress is applied from the outer portion 32 to the inner portion 31.

As a result, even when thermal stress is generated when the sensor element 10 is sintered, the end portion of the region in contact with the gas chamber 101 to be measured (that is, the inner portion 31 and the outer portion 32 between the opposing plates 3). It is possible to always maintain a state where compressive stress is generated at the boundary position. And the intensity | strength with respect to the compressive stress of ceramic material is remarkably higher than the intensity | strength with respect to the tensile stress. Therefore, it is possible to make it difficult for the counter plate 3 to crack at the end of the region in contact with the gas chamber 101 to be measured.

In addition, since the sintered density of the inner portion 31 is lowered, the heat retaining property by the inner portion 31 is improved. Thereby, the heat of the measurement gas G heated by the heat generating layer 41 of the heater substrate 4 is not easily radiated from the inner portion 31 to the outside of the sensor element 10. And the temperature distribution in a measurement gas chamber becomes small, and the detection accuracy of the gas concentration by the gas sensor 1 can be improved.

Therefore, according to the gas sensor 1 of the present embodiment, the counter plate 3 can be hardly cracked, and the temperature distribution (that is, the temperature difference) in the measured gas chamber 101 can be reduced.

(Confirmation test)
In this confirmation test, the difference between the sintered density of the inner portion 31 in the opposing plate 3 and the sintered density of the outer portion 32 in the opposing plate 3 (referred to as the sintered density difference) (%), and the gas chamber to be measured A test for confirming the strength of the opposing plate 3 and the NOx sensitivity of the gas sensor 1 when the width W1 of the inner portion 31 in the lateral direction B was changed with respect to the width W of the lateral direction B of 101 was performed.

In this confirmation test, the difference in the sintered density is in the range of 0.8% to 5.0%, and the width W1 in the lateral direction B of the inner portion 31 is in the range of 0.8W to 1.5W. Products 1-9 were tested. For comparison, tests were also performed on comparative products 1 to 5 in which the difference in sintering density or the width W1 in the lateral direction B of the inner portion 31 was out of the above ranges.

The strength was confirmed by performing a destructive test by thermal shock (that is, a crack generation confirmation test) and checking whether or not a crack occurred at the end of the counter plate 3 in the region in contact with the gas chamber 101 to be measured. This destructive test was performed based on the Charpy impact test, and the Charpy impact value, which is the required energy when the end portion of the sensor element 10 in contact with the gas chamber 101 to be measured was destroyed, was obtained. Then, the strength of the sensor element 10 was evaluated using this Charpy impact value as an index. In the strength evaluation, cracks did not occur in the destructive test but were overloaded, and the Charpy impact value when the crack was intentionally generated was rated as “excellent”. When the crack was intentionally generated in an overloaded state without generating a crack, the Charpy impact value was small.

The NOx sensitivity was confirmed by whether or not the measurement accuracy of the NOx concentration was lowered due to the temperature distribution generated in the measured gas chamber 101 when the NOx concentration was measured using the gas sensor 1. In the evaluation of NOx sensitivity, in the test, the NOx sensitivity did not decrease, the overloaded state required a large amount of energy when intentionally generating the NOx sensitivity decrease was considered “excellent”. No reduction in NOx sensitivity, no load required when the reduction in NOx sensitivity is intentionally caused in an overload state is defined as “good”, and no reduction in NOx sensitivity in the test is “impossible” "

Table 1 shows the sintered density difference between the test products 1 to 9 and the comparative products 1 to 5, the width W1 in the lateral direction B of the inner portion 31, and the results of this confirmation test.

For the

test products

2 and 3 in which the difference in sintering density is 1.0% or 3.0% and the width W1 in the lateral direction B of the inner portion 31 is 0.8 W, both strength and NOx sensitivity are “excellent”. became. From this result, it was found that the difference in the sintered density is most preferably in the range of 1.0 to 3.0% from the viewpoint of strength and NOx sensitivity.

Further, the difference in crystal density is 0.8%, 4.0%, or 5.0%, and the width W1 in the lateral direction B of the inner portion 31 is 0.8 W, 1.0 W, 1.4 W, and 1.5 W. For

certain test products

1 and 4 to 9, the strength was “good” and the NOx sensitivity was “excellent”. From this result, the sintered density difference is in the range of 0.8% to 5.0%, and the width W1 in the lateral direction B of the inner portion 31 is in the range of 0.8W to 1.5W. It was found that both strength and NOx sensitivity were excellent.

On the other hand, in the case where there is no difference in sintered density (that is, 0%), there is no inner portion 31 (the width W1 in the lateral direction B of the inner portion 31 is 0). Is less than 0.8% or more than 5.0%, or the comparative products 2 to 5 in which the width W1 in the lateral direction B of the inner part 31 is less than 0.8% or more than 1.5% And at least one of the NOx sensitivity was “impossible”. From this result, when the sintered density difference is less than 0.8% or more than 5.0%, or the width W1 in the lateral direction B of the inner portion 31 is less than 0.8% or more than 1.5%. It has been found that there is a possibility that cracks may occur at the end portion of the counter plate 3 in contact with the gas chamber 101 to be measured, or that the NOx concentration detection accuracy may be lowered.

DESCRIPTION OF SYMBOLS 1 Gas sensor 10 Sensor element 101 Gas chamber to be measured 102 Reference gas chamber 2 Solid electrolyte substrate 201 1st surface 202 2nd surface 3 Opposing plate 31 Inner part 32 Outer part 4 Heater substrate 41 Heating layer 51 First spacer 52 Second spacer G Gas to be measured A Reference gas

Claims

A solid electrolyte substrate (2) having oxygen ion conductivity;
A ceramic counter plate (3) disposed opposite the first surface (201) of the solid electrolyte substrate;
Ceramics sandwiched between the counter plate and the solid electrolyte substrate and forming a gas chamber (101) to be measured for allowing the gas to be measured (G) to flow between the counter plate and the solid electrolyte substrate A first spacer (51) made of
A heater layer (4) made of ceramics provided inside with a heat generating layer (41) that generates heat by energization and disposed opposite to the second surface (202) of the solid electrolyte substrate;
The ceramic substrate is sandwiched between the heater substrate and the solid electrolyte substrate and forms a reference gas chamber (102) for allowing a reference gas (A) to flow between the heater substrate and the solid electrolyte substrate. A second spacer (52),
The sintered density of the inner portion (31) including the region in contact with the gas chamber to be measured in the counter plate is 0.8 to less than the sintered density of the outer portion (32) including the region in contact with the first spacer. 5.0% lower gas sensor (1).
The gas sensor according to claim 1, wherein the sintered density of the outer portion is 95 to 100%.
The gas sensor according to claim 1 or 2, wherein the width (W1) of the inner portion is in the range of 0.8 to 1.5W, where W is the width of the gas chamber to be measured.