JP2005135868A - Ceramic heater, gas sensor element and manufacturing methods thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic heater capable of suppressing a change in resistance of a heating element resulting from repeated temperature rising and falling, and to provide a gas sensor element comprising the same and a manufacturing method of the gas sensor element. <P>SOLUTION: The ceramic heater 21 comprises the heating element 22 and a lead portion 23 connected to the heating element 22 for feeding a current thereto that are embedded in a ceramic insulating layer 24. A heating portion 26 made up of the heating element 22 and the ceramic insulating layer 24 covering the heating element 22 has a volume of 16 to 105 mm<SP>3</SP>, and the ratio of a common material of the heating element 22 is 36 to 46% by volume. This oxygen sensor element also comprises the ceramic heater 21. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ceramic heater, a gas sensor element, and a manufacturing method thereof, and more specifically, a ceramic heater suitable for a plate-like oxygen sensor element used for detecting an oxygen concentration in automobile exhaust gas, a gas sensor element including the ceramic heater, and The present invention relates to these manufacturing methods.

In recent years, environmental issues have been highlighted, and efforts are being made to put the global environment as a top priority in each industry. In particular, in the automobile industry, as represented by the exhaust gas regulations of California, USA, it has become a trend to reduce the amount of CO ₂ , CO, HC and NOx in exhaust gas year by year. . Among them, in order to further reduce the gas in the exhaust gas, it is important how to burn the fuel efficiently. For that purpose, the residual oxygen amount in the exhaust gas is instantaneously measured and the information is obtained. There is a growing demand for oxygen sensors that can provide fast feedback to the combustion system.

  Up to now, oxygen sensors have used a heat of exhaust gas to raise the temperature of a cylindrical sensor sealed at one end to develop a sensor function. However, until the sensor function appears, the exhaust gas is in a state of running down, and it has become impossible to meet the recent strict exhaust gas regulations. Therefore, an oxygen sensor that actively heats a cylindrical sensor with a heater has been developed. By using such an oxygen sensor, the sensor function can be expressed quickly, and information can be fed back more responsively.

  However, in the cylindrical sensor as described above, the size is inevitably increased, and the distance between the heater and the sensor is increased, so that the speed of the sensor function is limited.

  Therefore, recently, a plate-like oxygen sensor element has been developed in which the sensor part is made into a plate shape, and the temperature rise rate is increased by integrally forming the sensor part and the heater so that the sensor function can be expressed more quickly. An oxygen sensor provided is being developed (see, for example, Patent Document 1). The oxygen sensor described in Patent Document 1 uses a ceramic heater having a tip width of 4 mm and a common material ratio in the heating element of about 30% by volume. As described above, in recent years, the tip width of the ceramic heater is narrowed, and the volume of the heat generating part composed of the heating element and the insulating layer covering the heating element is reduced, thereby increasing the temperature rising rate of the oxygen sensor and improving the sensor function. Attempts have been made to develop it quickly. Usually, plate-shaped ceramic heaters and oxygen sensor elements are produced by stacking and adhering green sheets on which a heating element pattern is printed using printing paste, green sheets on which printing paste is not printed, etc., and firing them. ing.

However, in order to further increase the temperature rise rate of the oxygen sensor, the temperature rise rate of the oxygen sensor can be increased with a ceramic heater in which the tip width is reduced to about 2 to 3.5 mm and the volume of the heat generating portion is made smaller. However, there has been a problem that the resistance of the heating element is gradually changed by repeatedly raising and lowering the temperature, making it difficult to stably control the heater temperature and lowering the sensor performance.
Japanese Utility Model Publication No. 5-43495

  The subject of this invention is providing the ceramic heater which can suppress the change of the resistance of the heat generating body resulting from repetition of temperature rise and temperature fall, the gas sensor element provided with the same, and these manufacturing methods.

  As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention adjust the common material ratio in the heating element within a predetermined range in the ceramic heater in which the volume of the heating part is reduced in order to increase the temperature rising rate. Thus, the present inventors have found a new fact that a change in resistance of the heating element due to repeated temperature increase and decrease can be suppressed, and have completed the present invention.

That is, the ceramic heater of this invention, the gas sensor element provided with the same, and the manufacturing method of a gas sensor element consist of the following structures.
(1) A heating element and a lead connected to the heating element for supplying current to the heating element is a ceramic heater embedded in a ceramic insulating layer, the heating element and the heating element The ceramic heater is characterized in that the volume of the heat generating part constituted by the ceramic insulating layer covering the metal is 16 to 105 mm ³ and the common material ratio in the heat generating element is 36 to 46% by volume.
(2) The ceramic heater according to (1), wherein an outer dimension of the heat generating portion is 8 to 15 mm in length, 2 to 3.5 mm in width, and 1 to 2 mm in thickness.
(3) The ceramic heater according to (1) or (2), wherein the common material is ceramic for reducing a difference in thermal expansion coefficient between the heating element and the ceramic insulating layer.
(4) The ceramic heater according to any one of (1) to (3), wherein the common material has substantially the same composition as the ceramic insulating layer.
(5) A gas sensor element comprising the ceramic heater according to any one of (1) to (4).
(6) The gas sensor element according to (5), wherein the conductor contained in the heating element of the ceramic heater contains at least platinum.
(7) A step of preparing a heating element printing paste by mixing the conductor and the common material so that the common material ratio is 36 to 46% by volume, and using this printing paste, a heating element pattern is formed on the green sheet. A step of forming, a step of laminating another green sheet on the heating element pattern forming surface of the green sheet, and a step of firing the laminate of the obtained green sheets (1) to The method for producing a ceramic heater according to any one of (4).
(8) A step of preparing a heating element printing paste by mixing the conductor and the common material so that the common material ratio is 36 to 46% by volume, and using this printing paste, a heating element pattern is formed on the green sheet. A step of forming, a step of laminating a green sheet on which a sensor unit having a function of detecting a gas concentration is formed on the green sheet, and a step of firing the laminate of the obtained green sheets (5) The method for producing a gas sensor element according to (6), wherein

According to the ceramic heater described in the above (1) and (2), since the common material ratio in the heating element is adjusted to a predetermined range, the volume is in the range of 16 to 105 mm ³ , particularly the outer dimension is length 8. Even if it has a smaller heating part than conventional ones in the range of ~ 15mm, width of 2 ~ 3.5mm, thickness of 1 ~ 2mm, the resistance change of the heating element due to repeated heating and cooling Can be suppressed. That is, in the present invention, the ratio of the co-material in the heating element is made higher than before, and the difference in the thermal expansion coefficient between the heating element and the ceramic insulating layer covering the heating element is reduced, so that The difference in the degree of expansion and contraction between the heating element and the ceramic insulating layer at the time is reduced, and the generation and progress of cracks are suppressed. Thereby, the change of resistance of a heat generating body can be suppressed.

  Therefore, as described in (3) above, the difference in the thermal expansion coefficient between the heating element and the ceramic insulating layer can be reduced because the common material is ceramic. In particular, as described in (4) above, since the common material has substantially the same composition as the ceramic insulating layer, the difference in thermal expansion coefficient between the heating element and the ceramic insulating layer becomes smaller. The suppressing effect can be further enhanced.

  According to the gas sensor element of the above (5), since the above-described ceramic heater is provided, a stable sensor function can be obtained without excessively changing the resistance of the heating element even when repeatedly used for a long period of time. .

  Further, as described in (6) above, when the conductor included in the heating element contains at least platinum, it can be fired in an oxidizing atmosphere, and the manufacturing process can be simplified.

  As described in the above (7) and (8), according to the manufacturing method in which a plurality of green sheets, heating elements and the like are simultaneously fired, the manufacturing process is simplified and the cost can be reduced.

  Hereinafter, a ceramic heater, a gas sensor element, and a manufacturing method thereof according to the present invention will be described in detail with reference to the drawings. FIG. 1 (a) is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a plate-like oxygen sensor element provided with a ceramic heater according to an embodiment of the present invention, and FIG. 1 (b) is a cross-sectional view of this oxygen sensor element. It is sectional drawing which shows a cross section parallel to a longitudinal direction. FIG. 2A is an arrangement diagram for explaining the arrangement of the heating element and the lead part in the oxygen sensor element of FIG. 1, and FIG. 2B is an arrangement diagram showing another embodiment of the heating part. is there.

  As shown in FIGS. 1 (a), 1 (b) and 2 (a), the oxygen sensor element of the present embodiment is provided with a sensor unit 11 having a function of detecting the oxygen concentration and for heating the sensor unit 11. Ceramic heater 21 and ceramic layers 15, 16, and 25, and these are integrated by firing.

  The sensor unit 11 includes a solid electrolyte layer 12 having oxygen ion conductivity, a detection electrode 13 provided on the upper surface of the solid electrolyte layer 12, and a reference electrode 14 provided on the lower surface of the solid electrolyte layer 12. Yes. Lead portions 18 and 19 are connected to the detection electrode 13 and the reference electrode 14, respectively, and an electrode pad 31 (see FIG. 4 described later) is connected to an end portion of the lead portion 18. Is connected to an electrode pad 32. The electrode pad 32 is electrically connected to an electrode pad 33 provided on the upper surface of the solid electrolyte layer 12 through a through hole 37. From the viewpoint of preventing poisoning of the detection electrode 13 by exhaust gas, a ceramic porous layer (not shown) may be provided on the surface of the detection electrode 13 as an electrode protective layer.

  The ceramic heater 21 includes a heating element 22, a lead part 23 connected to the heating element 22 for supplying current to the heating element 22, and an electrode pad 34 connected to an end of the lead part 23. It is embedded in the insulating layer 24. The electrode pad 34 is electrically connected to an electrode pad 35 provided on the lower surface of the ceramic layer 25 through a through hole 36.

  The ceramic heater 21 and the solid electrolyte layer 12 constituting the sensor unit 11 are joined via a U-shaped ceramic layer 15 and a ceramic layer 16. Thus, the oxygen sensor element is formed with a cavity portion (atmospheric introduction hole) 17 whose one end is sealed. A ceramic layer 25 is laminated on the lower surface of the ceramic heater 21.

The heating part 26 composed of the heating element 22 and the ceramic insulating layer 24 covering the heating element 22 has a volume of 16 to 105 mm ³ , preferably 30 to 75 mm ³ . Further, the outer shape of the heat generating part 22 should be 8 to 15 mm in length L, preferably 10 to 13 mm, and 2 to 3.5 mm in width W, preferably 2.5 to 3.2 mm. The thickness t is 1 to 2 mm, preferably 1.2 to 1.8 mm. Thereby, the volume of the heat generating part 26 of the ceramic heater 21 can be reduced and the temperature increase rate of the oxygen sensor can be increased. Here, in the present embodiment, the heat generating part 26 is a heat generating element rather than the boundary between the heat generating element 22 and the lead part 23 in the ceramic heater 21 (shown by a one-dot chain line in FIGS. 1B and 2A). This is the site on the 22nd side (arrow A side). In the oxygen sensor element of the present invention, a heating element 22 ′ having a shape as shown in FIG.

  FIG. 3 is an enlarged cross-sectional view showing the outline of the main components constituting the heating element 22 in the ceramic heater 21 and the distribution state thereof. As shown in FIG. 3, the heating element 22 is mainly composed of a conductor 22a and a common material 22b. In the present invention, it is important that the common material ratio of the heating element 22 (ratio of the volume of the common material 22b in the heating element 22) is 36 to 46% by volume, preferably 38 to 44% by volume. The common material ratio can be represented by, for example, the area ratio of the common material 22b in the observation visual field area observed with an electron microscope or the like.

If the common material ratio is less than 36% by volume, the difference in the thermal expansion coefficient between the heating element 22 and the ceramic insulating layer 24 becomes large, so that the effect of suppressing the change in resistance of the heating element 22 may not be sufficiently obtained. is there. On the other hand, if the common material ratio exceeds 46% by volume, the resistance of the heating element 22 changes excessively, and it may be difficult to stably control the heater temperature.
In the ceramic heater 21 of the present invention, since the common material ratio is in the above range, the common material 22b is present in a moderately dispersed manner in the heating element 22, so that the conductor 22a grows when the temperature rises. Since the common material 22b inhibits this, the resistance value of the heating element 22 hardly changes. On the other hand, when the common material ratio is less than 36% by volume, the common material 22b existing in the heating element 22 decreases, and therefore the conductor 22a easily grows when the temperature rises, and the resistance value of the heating element 22 decreases. Sometimes. Further, if the common material ratio exceeds 46% by volume, the common material 22b present in the heating element 22 is excessively increased, and the conductivity is lowered. Grain growth proceeds excessively at that portion, and as a result, the resistance value may decrease.

  As the conductor 22a of the heating element 22, a known conductive metal material can be used, for example, platinum, tungsten, or an alloy of platinum and one selected from the group consisting of rhodium, palladium, lutetium, and gold is used. Is possible. Moreover, as an electrode material which comprises the detection electrode 13, the reference electrode 14, the lead | read | reed parts 18, 19, and 23 and the electrode pads 31-35, the material similar to the conductor 22a can be used. In particular, as the conductor 22a and the electrode material, platinum, tungsten, or the like is preferable because it can be fired simultaneously with the solid electrolyte layer 12 and the ceramic layers 15, 16, and 25.

  The material of the ceramic insulating layer 24 is not particularly limited as long as it is an insulating ceramic. For example, alumina, forsterite, or the like can be used. As the common material 22b, various ceramics useful in reducing the difference in thermal expansion coefficient from the ceramic insulating layer 24 can be used, and in particular, a material having substantially the same composition as the ceramic insulating layer 24 can be used. Specific examples of the common material 22b include alumina, forsterite, zirconia, mullite, titania and the like.

As a material constituting the solid electrolyte layer 12, a solid electrolyte such as zirconia or titania ceramics can be used. As this solid electrolyte, rare earth oxides such as Y ₂ O ₃ , Yb ₂ O ₃ , Sc ₂ O ₃ , Sm ₂ O ₃ , Nd ₂ O ₃ , and Dy ₂ O ₃ are used as stabilizers in terms of oxides. partially stabilized ZrO ₂ or stabilized ZrO ₂ containing 15 mol%, or the like may be used ZrO ₂ which was a solid solution of alkaline earth elements. The material of the other ceramic layers 15, 16 and 25 is not particularly limited, and the same solid electrolyte as the solid electrolyte layer 12 may be used, and various ceramic materials such as an alumina-containing material may be used. .

  In the oxygen sensor including the oxygen sensor element of the present embodiment, the reference atmosphere (oxygen) is introduced into the cavity 17 in a state where the heating element 22 is energized and the solid electrolyte layer 12 is heated to about 400 to 1000 ° C. The detection electrode 13 is disposed in a measurement atmosphere such as exhaust gas. Then, the electromotive force generated between the detection electrode 13 and the reference electrode 14 is measured, and the oxygen concentration in the exhaust gas is measured.

  Hereinafter, an example of a method for producing an oxygen sensor element including the ceramic heater 21 of the present invention will be described based on the exploded perspective view of FIG. In FIG. 4, the through holes 36 and 37 for electrode connection are omitted.

  First, the green sheets 12a, 12b, 15, 16, 25a, 25b, and 25c are produced by a known molding method such as tape molding using a doctor blade method. Next, a conductor and a common material are mixed to produce a printing paste for a heating element. The common material ratio in this printing paste is set to 36 to 46% by volume. The mixing method is not particularly limited, and for example, roll mixing such as three rolls, mill mixing using a mill, or the like can be used. Similarly, a printing paste for the detection electrode, a printing paste for the reference electrode, a printing paste for the ceramic insulating layer, and a printing paste for the electrode pad are prepared using roll mixing or the like.

  Next, the printing paste is applied to the green sheets 12a and 12b by screen printing or the like, and the electrode patterns of the detection electrode 13 and the reference electrode 14 are formed. These electrode patterns may be printed on both sides of one green sheet.

  Next, the printing paste 24b for the ceramic insulating layer is applied to the green sheet 25a by printing or the like and dried, and then the printing paste 22 for the heating element, the printing paste 23 for the lead portion, and the electrode are applied to the printing paste 24b by screen printing or the like. The pad printing paste 34 is applied to form each pattern, and the ceramic insulating layer printing paste 24a is applied onto the pattern and dried.

  Further, the electrode pad printing paste 35 is applied to the green sheet 25c by printing or the like to form a heater electrode pad pattern. Next, each green sheet on which various electrodes, ceramic insulating layers, heater patterns, etc. are formed, a green sheet 15 punched with a die in a U shape so as to be in contact with the reference atmosphere, a green sheet 16 for thickness adjustment, etc. are positioned. Then, the green body (laminated body of green sheets) is obtained. In order to adjust the thickness of the oxygen sensor element, another green sheet on which various patterns are not printed may be further interposed between the green sheets, and the present invention is not limited to FIG. Further, as described above, a heater material such as the heating element 22 may be included in the green sheet made of an insulating material without using the printing pastes 24a and 24b for the ceramic insulating layer.

Next, the green body is cut into a predetermined size as necessary. In that case, according to a heater pattern, it cuts so that the volume of the heat generating part 26 may be 16-105 mm < ³ > after baking. In particular, it is preferable to cut the tip width W to be 2 to 3.5 mm. If the tip width W after firing is less than 2 mm, there is a possibility that alignment of position accuracy and cutting conditions during lamination are difficult. Further, if the tip width W exceeds 3.5 mm, the ceramic heater itself becomes large, and it may be difficult to quickly raise the temperature.

  Next, a green body having various electrodes, insulating layers, heater patterns, and the like is fired simultaneously. The firing temperature can be appropriately selected according to the relationship with the ceramic material and the electrode material. By simultaneous firing, the firing step can be performed once, and the cost can be reduced.

In addition, in the range which does not deviate from the objective of this invention, the structure of a ceramic heater and an oxygen sensor element is not limited only to the said embodiment. For example, in the above-described embodiment, the case where the present invention is applied to an oxygen sensor element has been described. However, the present invention is also applicable to a gas sensor element having a similar structure such as a NOx sensor and a CO ₂ sensor.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to a following example.

<Production of oxygen sensor element>
First, a partially stabilized zirconia powder to which yttria having an average particle diameter of 0.8 μm was added was mixed with a butyral binder, a solvent and a medium, and stirred for 48 hours to obtain a slurry. Thereafter, the slurry was molded and dried by doctor blade molding to produce a green sheet having a thickness of 200 μm.

  Next, butyral binder and terpineol are mixed with platinum powder having an average particle diameter of 1 μm, mixed 10 times with three rolls, diluted with terpineol, viscosity adjusted, and for detection electrode and reference electrode Then, printing pastes for lead portions and electrode pads were obtained.

  Various electrode patterns were formed on the green sheet by screen printing using the obtained electrode paste, and then dried to obtain a green sheet on which an electrode was formed.

  On the other hand, after mixing butyral binder and terpineol with alumina powder having an average particle size of 0.5 μm, mixing 10 passes with 3 rolls, diluting with terpineol, adjusting viscosity, printing for ceramic insulation layer A paste was obtained.

  Further, partially stabilized zirconia powder or alumina is mixed with platinum powder having an average particle diameter of 1 μm so that the co-material ratio becomes the value shown in Table 1, and a butyral binder and terpineol are further mixed into a three roll. After 10 times of mixing, the mixture was diluted with terpineol and the viscosity was adjusted to obtain a printing paste for a heating element.

  Using the printing paste for the ceramic insulating layer obtained above, a printing pattern of the ceramic insulating layer is formed on the green sheet by screen printing and dried, and then the heating paste printing paste for the lead portion The printing paste for the electrode pad and the electrode pad printing paste are formed by screen printing and dried, and then the printed pattern for the ceramic insulating layer is formed thereon by screen printing and dried. A ceramic insulating layer was formed on the green sheet.

  The green sheet located in the cavity portion in contact with the reference atmosphere was produced by punching in a U shape with a mold so that the width of the cavity portion was 1.2 mm. Next, various green sheets having a total number of laminated layers of 10 including a green sheet on which a ceramic insulating layer with a heater is formed are positioned, adhered and laminated using an adhesion liquid, and pressed to form a green body (oxygen sensor). Element molded body) was obtained.

Thereafter, the green body was cut with a hot knife heated to 130 ° C. so that the outer dimension of the heat generating portion became the value shown in Table 1 after firing. And this green body was baked at 1400 degreeC for 2 hours, and obtained each five oxygen sensor elements of sample No. 1-19. In each sample, in order to prevent cracks due to heat shock from occurring on the ridge surface near the heat generating part in the accelerated intermittent durability test, as shown in FIG. 5, the oxygen sensor element in the vicinity where the heat generating element is incorporated C surface processing was given to the lower surface side corner.

<Performance evaluation>
Resistance change rate: Each oxygen sensor element is heated to 1150 ° C. in 1 minute and accelerated intermittent endurance test in which the temperature is lowered to 30 ° C. in 1 minute is performed for 10,000 cycles, and the resistance value between the heater electrode pads after the test is measured. The rate of change in resistance was calculated from the resistance value after the test and the resistance value before the test. The test was performed for five samples, and the average of the five samples was defined as the average resistance change rate. The resistance change rate is obtained by dividing the difference between the resistance value after the test and the resistance value before the test (after the test-before the test) by the resistance value before the test and multiplying by 100.
Rate of temperature increase: A voltage of 22 V was applied to the ceramic heater to measure the time required to raise the temperature from 30 ° C. or lower to 900 ° C.
Strength: “NG” was indicated in the table for those in which the tip of the element was damaged due to processing resistance during the C-surface processing, and “OK” was indicated for those in which no damage occurred.

The results are shown in Table 1. From Table 1, it can be seen that the sample No. 1 having a common material ratio exceeding 46% has a problem in strength because breakage occurred during the C-face machining. Sample No. 9 in which the common material ratio exceeds 46% has an average resistance change rate of −3.0, which is greatly reduced. When the common material ratio is large, it is difficult to energize, and it is considered that the grain growth of the conductor in the heating element progressed during the durability test, and the resistance was lowered. Sample No. 4 having a common material ratio of less than 36% by volume has a resistance change rate of −1.0, which is greatly reduced. Samples 12 and 13 in which the volume of the heat generating part exceeds 105 mm ³ have a slow temperature increase rate. On the other hand, Sample Nos. 2, 3, 5 to 8, 10, 11, and 14 to 19 within the scope of the present invention have a high temperature rising rate, a small resistance change rate, and excellent strength.

(a) is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a plate-like oxygen sensor element provided with a ceramic heater according to an embodiment of the present invention, (b) is parallel to the longitudinal direction of this oxygen sensor element It is sectional drawing which shows a various cross section. (a) is an arrangement view for explaining the arrangement of the heating element and the lead part in the oxygen sensor element of FIG. 1, and (b) is an arrangement view showing another embodiment of the heating part. It is an expanded sectional view which shows the outline of the main components which comprise the heat generating body in the ceramic heater of this invention, and these distribution states. It is a disassembled perspective view for demonstrating the manufacturing method of the oxygen sensor element of this invention. It is a perspective view which shows the sample (oxygen sensor element) which performed C surface processing in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Sensor part 12 Solid electrolyte layer 13 Detection electrode 14 Reference electrode 15, 16, 25 Ceramic layer 17 Cavity part 18, 19 Lead part 21 Ceramic heater 22 Heat generating element 22a Conductor 22b Common material 23 Lead part 24 Ceramic insulating layer 26 Heat generating part

Claims (8)

A heating element and a lead portion connected to the heating element to supply a current to the heating element is a ceramic heater embedded in a ceramic insulating layer,
The volume of the heat generating part composed of the heat generating element and the ceramic insulating layer covering the heat generating element is 16 to 105 mm ³ , and the common material ratio in the heat generating element is 36 to 46% by volume. Ceramic heater.   2. The ceramic heater according to claim 1, wherein outer dimensions of the heat generating portion are 8 to 15 mm in length, 2 to 3.5 mm in width, and 1 to 2 mm in thickness.   The ceramic heater according to claim 1 or 2, wherein the common material is ceramic for reducing a difference in thermal expansion coefficient between the heating element and the ceramic insulating layer.   The ceramic heater according to claim 1, wherein the common material has substantially the same composition as the ceramic insulating layer.   A gas sensor element comprising the ceramic heater according to claim 1.   The gas sensor element according to claim 5, wherein the conductor contained in the heating element of the ceramic heater contains at least platinum.   A step of mixing a conductor and a common material so that the common material ratio is 36 to 46% by volume to produce a heating element printing paste, and a step of forming a heating element pattern on a green sheet using the printing paste And a step of laminating another green sheet on the heating element pattern forming surface of the green sheet, and a step of firing the obtained green sheet laminate. A method for producing a ceramic heater according to claim 1. A step of mixing a conductor and a common material so that the common material ratio is 36 to 46% by volume to produce a heating element printing paste, and a step of forming a heating element pattern on a green sheet using the printing paste And a step of laminating a green sheet on which a sensor unit having a function of detecting a gas concentration is formed on the green sheet, and a step of firing the obtained green sheet laminate, A method for producing a gas sensor element according to claim 5 or 6.

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