JP4224011B2 - Gas sensor and gas concentration measuring method - Google Patents

Description

  The present invention relates to a gas sensor and a gas concentration measuring method capable of measuring the concentration of a predetermined gas in a gas to be measured.

Conventionally, as a sensor for measuring the oxygen concentration in air, for example, a λ sensor whose output changes suddenly at a theoretical air-fuel ratio is known.
In this λ sensor, for example, electrodes are formed on the outside and inside of a cup-shaped substrate made of a solid electrolyte, a reference gas is introduced inside, and a gas to be measured is introduced outside. The oxygen concentration (theoretical air-fuel ratio) in the gas to be measured is to be detected by the electromotive force that is generated (see Patent Document 1).

In addition, a so-called limiting current type gas sensor has been proposed. This limiting current type gas sensor is provided with a negative electrode and a positive electrode on both sides of a solid electrolyte substrate, and a diffusion rate-limiting part for limiting the diffusion of the gas to be measured on the negative electrode side. The oxygen concentration is measured by using the fact that the current (limit current) flowing from the negative electrode to the positive electrode by applying the voltage is proportional to the oxygen concentration in the measurement gas (see Patent Document 2). .
JP-A-11-160275 (page 3, FIG. 1) Japanese Patent Laid-Open No. 10-318975 (page 3, FIG. 1)

However, the above-described conventional λ sensor technology has a problem in that the configuration is complicated because it is necessary to introduce the reference gas into the inside of the cup-shaped substrate.
In addition, although the limiting current type gas sensor can measure the oxygen concentration with high accuracy, there is a problem that the structure is further complicated because it is necessary to provide a diffusion rate controlling part.

  The present invention has been made to solve the above-mentioned problems, and has as its object the gas sensor and gas concentration measurement capable of measuring a wide range of gas concentrations while simplifying the structure without requiring a reference gas or the like. Is to provide a method.

(1) The invention of claim 1 has a sensor element in which at least one pair of electrodes is provided on a substrate mainly composed of a solid electrolyte, and is based on electrical characteristics (for example, potential difference) between the paired electrodes. In the gas sensor for detecting the concentration of a predetermined gas in the gas to be measured, one electrode of the pair of electrodes is a reference electrode containing nickel manganate (NiMn ₂ O ₄ ) , and the reference electrode The other electrode forming the above is a detection electrode.

In the present invention, for example, a pair of electrodes is provided on a solid electrolyte substrate, and one of the paired electrodes is a reference electrode containing nickel manganate (NiMn ₂ O ₄ ). The other electrode paired with the reference electrode is the detection electrode. Therefore, by exposing the sensor element to the gas to be measured and bringing both electrodes into contact with the measurement gas, for example, the concentration of the predetermined gas can be measured from the potential difference between the electrodes.

Here, the detection electrode is an electrode that causes an electrochemical reaction (for example, an equilibrium reaction between oxygen molecules and oxygen ions) to reach a certain gas more smoothly than the counterpart reference electrode. In this detection electrode, the equilibrium state of the electrochemical reaction changes corresponding to the concentration of the predetermined gas. On the other hand, the reference electrode is a gas inert electrode in which the equilibrium state of the electrochemical reaction at the interface between the electrode and the solid electrolyte does not change or hardly changes even if the type or concentration of the gas in contact changes. .
Accordingly, since the equilibrium state of the electrochemical reaction with respect to the predetermined gas is different between the reference electrode and the detection electrode, the concentration of the predetermined gas can be obtained from the electrical characteristics (for example, potential difference) between the two electrodes.
That is, when the reference electrode containing nickel manganate (NiMn ₂ O ₄ ) is used, an electrochemical reaction (for example, oxygen molecules and oxygen) with respect to a predetermined gas as compared with a conventional normal electrode made of platinum or the like. (Equilibrium reaction with ions) is limited, so that the concentration of the predetermined gas can be determined from, for example, a change in electrical characteristics such as a potential difference between the two electrodes.

Therefore, there is no need for a reference gas or the like as in the conventional λ sensor, the structure can be simplified, and a wide range of gas concentrations can be measured.
The reference electrode is preferably composed of the nickel manganate (NiMn ₂ O ₄ ) as a main component (or the entire electrode is the nickel manganate (NiMn ₂ O ₄ )) .

Incidentally, the measurement of the gas concentration, it is also intended to be included detection of the presence or absence of the substance.

( 2 ) The invention of claim 2 is characterized in that a potential difference between the reference electrode and the detection electrode is measured, and a concentration of a predetermined gas in the measurement gas is measured based on the potential difference.

In the present invention, when both electrodes come into contact with the gas to be measured, the equilibrium state of the electrochemical reaction between the two electrodes is different, so that a potential difference is generated between the two electrodes. Therefore , the concentration of the predetermined gas can be measured from the potential difference between the reference electrode and the detection electrode .

( 3 ) The invention of claim 3 is characterized in that the predetermined gas is oxygen gas.
The present invention exemplifies a predetermined gas. When both electrodes are in contact with oxygen gas, the equilibrium state of the electrochemical reaction at both electrodes is different, and a potential difference is generated between the two electrodes, so that the gas concentration can be determined from the potential difference.

( 4 ) The invention of claim 4 is characterized in that the solid electrolyte is stabilized zirconia.
The present invention illustrates a solid electrolyte. By exposing the solid electrolyte provided with the pair of electrodes to a gas to be measured containing oxygen gas or the like, a potential difference (electromotive force) corresponding to the oxygen concentration is generated between both electrodes, and thus the oxygen concentration or the like is obtained from the potential difference. Can do.

( 5 ) The invention of claim 5 is characterized in that the detection electrode is an electrode mainly composed of a platinum group or a platinum group alloy.
The present invention exemplifies a detection electrode. By using an electrode whose main component is this platinum group or a platinum group alloy, a stable potential difference is generated, so that the oxygen concentration and the like can be suitably measured.

( 6 ) The invention of claim 6 is characterized in that the measurement temperature when measuring the concentration of the gas is 300 to 700 ° C.
The present invention exemplifies a preferred operating temperature range of the gas sensor of the present invention (and hence the temperature near the electrode of the sensor element).

( 7 ) The invention of claim 7 includes a temperature sensor and / or a heater.
In the present invention, since the temperature sensor and the heater are provided, for example, the temperature of the gas to be measured is controlled by checking the temperature of the sensor element and its surroundings (that is, the measurement temperature) with the temperature sensor and controlling the temperature to a predetermined temperature with the heater. Even when the gas sensor is low or the gas sensor has temperature dependence, the gas concentration can always be accurately measured.

  In addition, what has only a temperature sensor measures temperature, For example, you may make it measure gas concentration in the case of a predetermined preferable temperature range. In addition, in the case where only the heater is provided, the measurement temperature can be kept substantially constant by heating with a predetermined heating pattern, for example.

( 8 ) The invention according to claim 8 uses a sensor element in which at least one pair of electrodes is provided on a base body having a solid electrolyte as a main component, and based on electric characteristics between the paired electrodes, In the gas concentration measurement method for detecting the concentration of the predetermined gas, a reference electrode containing nickel manganate (NiMn ₂ O ₄ ) is used as one of the pair of electrodes, and the reference is used as the other electrode. A sensing electrode that is paired with an electrode is used, the sensor element is disposed in the gas to be measured, and both electrodes are brought into contact with the measuring gas to measure the concentration of the predetermined gas.

As described in the first aspect of the present invention, in the present invention, a pair of electrodes of a reference electrode and a detection electrode is provided on a solid electrolyte substrate, and manganese nickel (NiMn ₂ O ₄ ) is contained in the reference electrode. Yes. Therefore, as is clear from the experimental examples described later, by exposing the sensor element to the gas to be measured and bringing both electrodes into contact with the measurement gas, for example, the concentration of the predetermined gas can be measured from the potential difference between the two electrodes. it can.
That is, since the equilibrium state of the electrochemical reaction with respect to the predetermined gas is different between the reference electrode and the detection electrode, the concentration of the predetermined gas can be obtained from the electrical characteristics (for example, potential difference) between the two electrodes.

(9 ) The invention of claim 9 is characterized in that a potential difference between the reference electrode and the detection electrode is measured, and a concentration of a predetermined gas in the measurement gas is measured based on the potential difference.

The present invention has the same effects as the invention of the second aspect .

( 10 ) The invention of claim 10 is characterized in that the concentration of the predetermined gas is measured without using a reference gas or a reference gas for the reference electrode.
In the present invention, not only the detection electrode but also the reference electrode can be exposed to the gas to be measured to measure the concentration of the predetermined gas. Therefore, it is not necessary to use a reference gas or a reference gas that is a standard as in the conventional case, and the structure of the sensor can be simplified.

( 11 ) The invention of claim 11 is characterized in that the measurement temperature when measuring the concentration of the gas is set to 300 to 700 ° C.
The present invention exemplifies a preferable use temperature range of the gas sensor of the present invention.

  Next, an example (example) of the best mode of the gas sensor and gas concentration measuring method of the present invention will be described.

a) First, the system configuration of the gas sensor of this embodiment will be described.
As shown in FIG. 1, a gas sensor (gas concentration measuring device) 1 of this embodiment is an oxygen sensor that measures the concentration (gas concentration) of oxygen gas in a gas to be measured, and includes a sensor element 3 and a sensor element 3. The temperature adjusting unit 5 for adjusting the temperature of the gas sensor and the gas measuring unit 7 for measuring the gas concentration by a signal from the sensor element 3 are configured.

  The sensor element 3 includes a test tubular base 9 whose front end (left side in the figure) is closed and a rear end is opened, and a reference electrode 11 formed in an annular shape on the front end side of the outer peripheral surface of the side of the base 9. The outer peripheral surface is constituted by a detection electrode 13 formed in an annular shape on the rear end side from the reference electrode 11, and the reference electrode 11 and the detection electrode 13 are respectively connected to the gas measuring unit 7. Lead portions 15 and 17 are provided.

Of these, the substrate 9 is a solid electrolyte and is made of stabilized zirconia (YSZ) to which yttria is added. The reference electrode 11 is an electrode composed mainly of manganese, nickel (NiMn ₂ O _4), the detection electrode 13 is an electrode composed mainly of platinum.

  The temperature adjusting unit 5 includes a thermocouple (temperature sensor) 21 and a heater 23 arranged in the internal space 19 of the base 9, and a temperature controller 25 which is an electronic control device connected to the thermocouple 21 and the heater 23. It is configured.

  The temperature controller 25 obtains the temperature of the sensor element 3 from the electromotive force of the thermocouple 21 (accordingly, the measurement temperature which is the temperature of the measurement site), and the sensor element 3 becomes a predetermined measurement temperature based on the measurement temperature. Similarly, the heater 23 is energized to control the sensor element 3 to be heated.

  Here, the temperature is adjusted using the thermocouple 21, the heater 23, and the temperature controller 25, but the configuration is not limited to this as long as the temperature can be adjusted. Moreover, when temperature adjustment is not required, these may be omitted. Furthermore, the heater 23 is not necessarily disposed inside the sensor element 3 as long as it can heat the sensor element 3. For example, it may be arranged outside the sensor element 3 or may be embedded in the substrate 9.

  The gas measuring unit 7 is connected to the lead units 15 and 17, and obtains an oxygen concentration from a digital electrometer 27 that measures a potential difference (voltage) between the reference electrode 11 and the detection electrode 13, and the measured potential difference. An electronic control device 29 and a display 31 for displaying the oxygen concentration obtained by the electronic control device 29 are provided.

  Therefore, in the present embodiment, by using the sensor element 3, the temperature adjusting unit 5, and the gas measuring unit 7, as described in detail later, based on the potential difference between the electrodes 11 and 13, The concentration of oxygen gas can be obtained.

b) Next, the manufacturing method of the sensor element 3 which is the principal part of the gas sensor 1 of a present Example is demonstrated.
First, yttria with a purity of 99% or more was blended at a ratio of 8 mol with respect to zirconia (ZrO ₂ ): 100 mol with a purity of 99% or more, wet-mixed, and then calcined at a temperature of 1300 ° C.

Water was added to the calcined product and pulverized with a ball mill, and then a water-soluble binder was added and granulated by a spray drying method.
This granulated product was formed into a cup-shaped bottomed cylindrical shape (or flat plate shape: Examples 2 and 3) by a rubber press method, and ground with a grindstone to adjust the shape.

Next, this molded body was fired at a temperature of 1500 ° C. for 3 hours to obtain a substrate 9 made of a solid electrolyte zirconia ceramic.
For the reference electrode 11, 20 wt% polyethylene glycol (PEG) is added as a binder to nickel manganate (NiMn ₂ O ₄ ) powder, and α-terpineol is mixed as a solvent so as to have an appropriate viscosity. A paste was prepared. For example, a paste mixed at a weight ratio of “(powder + binder): solvent = 2: 1” was prepared.

  Further, for detection electrode 13, a paste was prepared by adding 10% by weight of ethylcellulose as a binder to platinum (Pt) powder, and mixing perpineol (trade name) as a solvent to an appropriate viscosity. .

  Next, the paste for the reference electrode 11 is applied in an annular shape (in a belt shape) on the outer peripheral surface on the side of the distal end side of the substrate 9. Similarly, the paste for the detection electrode 13 was also applied in an annular shape on the outer peripheral surface on the side of the distal end side of the substrate 9.

  And after apply | coating each paste, it was made to dry in 130 degreeC dryer for 1 hour, after that, the base | substrate 9 was put into a tubular furnace, and it baked at 1400 degreeC for 2 hours by air | atmosphere atmosphere, the reference electrode 11 and detection A substrate 9 provided with the electrode 13, that is, the sensor element 3 was obtained.

  As the detection electrode 13, a platinum thin film having a thickness of 1 to 2 microns may be formed by an electroless platinum plating method. Further, the thermocouple 21 and the heater 23 may be arranged in the sensor element 3 after the sensor element 3 is completed.

c) Next, a gas concentration measurement method using the gas sensor 1 of the present embodiment will be described.
As a gas concentration measuring method of the present embodiment, a gas to be measured (for example, engine exhaust gas) containing oxygen gas as a predetermined gas is used.

Then, both electrodes 11 and 13 of the sensor element 3 are exposed to the gas to be measured, and the heaters 23 keep both the electrodes 11 and 13 at a predetermined temperature within a range of 300 to 700 ° C.
At this time, the reference electrode 11 side shows a constant potential due to the constituent component of the reference electrode 11 (ie, NiMn ₂ O ₄ ), but on the detection electrode 13 side, due to the constituent component of the detection electrode 13 (ie, Pt), The electrochemical reaction according to the concentration of oxygen gas reaches equilibrium.

  That is, since the electrochemical reaction involving oxygen molecules and oxygen ions reaches equilibrium mainly on the detection electrode 13 side, a potential difference is generated between the electrodes 11 and 13, and this potential difference is detected by the digital electrometer 27. At the same time, the gas measuring unit 7 determines the concentration of oxygen gas based on this potential difference.

  That is, the potential on the reference electrode 11 side is inactive with respect to the change in the concentration of oxygen gas, but on the detection electrode 13 side, the electrochemical reaction reaches equilibrium in accordance with the oxygen concentration. Based on this potential difference, the concentration of oxygen gas can be determined.

  As described above, in this embodiment, the sensor element 3 of the gas sensor 1 includes the zirconia solid electrolyte base 9, the reference electrode 11 mainly composed of nickel manganate, and the detection electrode 13 mainly composed of platinum. Since the electromotive force corresponding to the oxygen concentration can be obtained by exposing the electrodes 11 and 13 to the gas to be measured using the provided element, the oxygen concentration of the gas to be measured can be obtained from the electromotive force. .

  Therefore, it is not necessary to introduce a reference gas or the like as in the conventional λ sensor, the structure can be simplified, the conventional diffusion limiting means can be omitted, and a wide range of gas concentrations can be measured. There is a remarkable effect of being able to.

Further, by using this gas sensor, the oxygen concentration can be suitably measured particularly at a measurement temperature of 300 to 700 ° C.
d) Next, an experimental example performed to confirm the effect of the present embodiment will be described.

(1) Experimental example 1
In Experimental Example 1, the response (electromotive force: sensor output) to each gas when using the reference electrode within the scope of the present invention was examined.

  As shown in FIG. 2, in the present experimental example, the reference electrode K and the outer detection electrode Pt-out are provided outside the substrate, and the potential difference between the two electrodes is measured with the first voltmeter V1 as in the first embodiment. It was set as the structure to do. Further, an inner detection electrode Pt-in (similar to the outer detection electrode Pt-out) is also provided inside the substrate, and the potential difference between the reference electrode K and the inner detection electrode Pt-in is measured with the second voltmeter V2. It was set as the structure to do.

  In addition, air was supplied to the internal space of the sensor element as a reference gas for experiments. The gas sensor of the present invention does not require a reference gas, but here, the reference gas was used for experiments.

Then, the measurement temperature was set to 600 ° C., and 6 kinds of gases were supplied at a flow rate of 100 cm ³ / min at intervals of 5 minutes every 5 minutes. Specifically, a gas to be measured was supplied by adding 400 ppm each of six gases of CO, CH ₄ , C ₃ H ₈ , H ₂ , NO, and NO _{2 to} the base gas. The base gas contains nitrogen in an amount of 5% oxygen (hereinafter, gas concentration% indicates volume%) and water vapor 5%.

  Then, the potential difference (electromotive force EMF) generated between the reference electrode K and the outer detection electrode Pt-out when the gas to be measured was supplied was measured. Similarly, the potential difference generated between the reference electrode K and the inner detection electrode Pt-in was also measured.

  The result is shown in FIG. In FIG. 3, the vertical axis represents electromotive force and the horizontal axis represents time (minutes). As is apparent from FIG. 3, the gas sensor of this experimental example does not show any particular response to various gases, so that it can be seen that there is no risk of erroneous detection when oxygen gas is detected.

(2) Experimental example 2
In Experimental Example 2, the dependency of the oxygen concentration on the sensor output of the gas sensor of the present invention was examined.

In this experimental example, the same sensor element as in Experimental Example 1 was used, and air was supplied as a reference gas to the internal space of the sensor element.
Then, the measurement temperature was set to 600 ° C., and five kinds of gases having different oxygen concentrations were supplied at a flow rate of 100 cm ³ / min at intervals of 3 minutes every 5 minutes. Specifically, five types of gases having different oxygen concentrations, including 5%, 10%, 20%, 50%, and 80% oxygen gas (as a predetermined gas to be measured) are added to the nitrogen gas that is the base gas. Supplied. As the measurement gas, one containing 5% water vapor and one containing no water vapor were supplied.

  Then, a potential difference (electromotive force EMFgas) generated between the reference electrode K and the outer detection electrode Pt-out when the measurement gas was supplied was measured. Further, the potential difference (electromotive force EMFbase) when the base gas was supplied was measured. Furthermore, the difference ΔEMF (= EMFgas−EMFbase) between the two electromotive forces was obtained as the sensitivity of the gas sensor.

  The result is shown in FIG. FIG. 4 shows the detection electrode (outside detection electrode Pt-out) as a reference. The vertical axis represents sensitivity ΔEMF and the horizontal axis represents logarithmic oxygen concentration. As is clear from FIG. 4, it can be seen that the gas sensor of this experimental example can obtain a sensitivity corresponding to the oxygen concentration. Therefore, it can be seen that the oxygen concentration can be obtained from the sensitivity based on the electromotive force.

FIG. 5 is a graph obtained by rewriting FIG. 4 with reference electrodes as references. As is clear from FIG. 5, it can be seen that the sensitivity of the gas sensor of this experimental example increases as the oxygen concentration increases.
(3) Experimental example 3
In Experimental Example 3, the dependency of oxygen concentration on the sensor output of the gas sensor of the present invention was examined.

In this experimental example, the same sensor element as in Experimental Example 1 was used, and air was supplied as a reference gas to the internal space of the sensor element.
Then, the measurement temperature was set to 600 ° C., and five kinds of gases having different oxygen concentrations were supplied at a flow rate of 100 cm ³ / min at intervals of 3 minutes every 5 minutes. Specifically, five types of measured gases having different oxygen concentrations including 5%, 10%, 20%, 50%, and 80% of oxygen gas were supplied to the nitrogen gas as the base gas. As the measurement gas, one containing 5% water vapor and one containing no water vapor were supplied.

  Then, a potential difference (electromotive force EMFgas) generated between the reference electrode K and the inner detection electrode Pt-in when the gas to be measured was supplied was measured. Further, the potential difference (electromotive force EMFbase) when the base gas was supplied was obtained. Furthermore, the difference ΔEMF (= EMFgas−EMFbase) between the two electromotive forces was obtained as the sensitivity of the gas sensor.

The result is shown in FIG. FIG. 6 shows the detection electrode (inner detection electrode Pt-in) as a reference, with the vertical axis representing sensitivity and the horizontal axis representing logarithmic oxygen concentration.
In this experiment, the reference electrode K is in contact with the gas to be measured whose oxygen concentration changes, and the inner detection electrode Pt-in is in contact with the reference gas whose oxygen concentration does not change. As is clear from FIG. I understand that there is no.

That is, it can be seen that the electrochemical reaction hardly occurs at the reference electrode in contact with the gas to be measured, and thus the function as the reference electrode is exhibited.
(4) Experimental example 4
In this experimental example, as shown in FIG. 7, the reference electrode K and the inner detection electrode Pt-in are provided, and the potential difference between both electrodes is measured with a voltmeter. Other configurations are the same as those of the first embodiment. In addition, air was supplied to the internal space of the sensor element as a reference gas for experiments. In addition, PEG was not used when producing the reference electrode.

Then, the measurement temperatures were 500 ° C., 550 ° C., 600 ° C., and 700 ° C., and gases with different oxygen concentrations were supplied at a flow rate of 100 cm ³ / min. Specifically, oxygen gas is added to nitrogen gas as a base gas at 0%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 5%, 10%, 20 %, 50%, and 80% of the measurement gas were supplied, and the potential difference (electromotive force EMF) generated between the reference electrode K and the inner detection electrode Pt-in was measured.

The results are shown in FIGS. 8 to 11, the vertical axis represents electromotive force and the horizontal axis represents time (minutes). Note that% shown in FIGS. 8 to 11 is also volume% (of oxygen concentration).
In the experiments at 500 ° C. and 600 ° C. shown in FIGS. 8 and 10, the oxygen concentration was set to 80% after 50 minutes had elapsed since the start of the experiment. In the experiment at 550 ° C. shown in FIG. 9, the oxygen concentration was set to 0% after 55 minutes had elapsed since the start of the experiment. Furthermore, in the experiment at 700 ° C. shown in FIG. 11, the oxygen concentration was set to 20% for 40 to 130 minutes after the start of the experiment.

  In this experiment, the reference electrode K is in contact with the gas to be measured whose oxygen concentration changes, and the inner detection electrode Pt-in is in contact with the reference gas whose oxygen concentration does not change. As is apparent from FIGS. It can be seen that at the measurement temperatures of 500 ° C. and 550 ° C., the electromotive force between the two electrodes hardly changes even if the oxygen concentration changes.

  In other words, at this measurement temperature, it can be seen that the reference electrode in contact with the gas to be measured maintains the equilibrium state of the electrochemical reaction regardless of the oxygen concentration, and thus exhibits the function as the reference electrode.

  On the other hand, as is apparent from FIG. 10, when the measurement temperature is 600 ° C., the electromotive force gradually increases from the case where the oxygen concentration is 5% or more, and at 80%, the electromotive force increases rapidly. As is clear from FIG. 11, when the measurement temperature is 700 ° C., the electromotive force increases rapidly when the oxygen concentration is 5% or more.

  Therefore, when the measurement temperature is high, it can be seen that there is a limit to the range of the measured concentration as it is.

Next, the second embodiment will be described, but the description of the same parts as the first embodiment will be omitted.
This embodiment differs from the first embodiment in the structure of the sensor element.
As shown in FIG. 12, the sensor element 43 of the gas sensor 41 of the present embodiment includes a reference electrode 47 mainly composed of nickel manganate (NiMn ₂ O ₄ ) on both sides of a flat substrate (substrate) 45. A detection electrode 49 containing Pt as a main component is disposed, and the reference electrode 47 and the detection electrode 49 are configured to be in contact with the gas to be measured.

  In addition, a heater substrate 51 is arranged in parallel in the vicinity of the substrate 45 through a gap, and a thermocouple and a heater for detecting temperature are arranged in the heater substrate 51 (FIG. Not shown).

In addition to the gas measuring unit 53 that measures the oxygen concentration from the potential difference between the electrodes 47 and 49, a temperature controller or the like (not shown) is connected as in the first embodiment.
This embodiment also has the advantages that the same effects as those of the first embodiment can be obtained and the structure of the sensor element 43 can be simplified.

Next, although Example 3 will be described, description of the same parts as those in Example 1 will be omitted.
This embodiment differs from the first embodiment in the structure of the sensor element.
As shown in FIG. 13, the sensor element 63 of the gas sensor 61 of the present embodiment is mainly composed of nickel manganate (NiMn ₂ O ₄ ) on one surface (upper surface in the figure) of a flat substrate (substrate) 65. A reference electrode 67 as a component and a detection electrode 69 mainly composed of Pt are arranged side by side, and the reference electrode 67 and the detection electrode 69 are configured to be in contact with the gas to be measured.

  A heater substrate 71 is bonded to the other surface (lower surface) of the substrate 65, and a thermocouple and a heater for detecting temperature are disposed in the heater substrate 71 (not shown). )

In addition to the gas measuring unit 73 that measures the oxygen concentration from the potential difference between the electrodes 67 and 69, a temperature controller or the like (not shown) is connected as in the first embodiment.
This embodiment also has the advantages that the same effects as those of the first embodiment can be obtained, the structure of the sensor element 63 can be simplified, and the strength thereof can be improved.

In addition, this invention is not limited to the said Example at all, and it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from the summary of this invention.
(1) For example, in the above embodiment, as a reference electrode, but using an electrode composed mainly of manganese, nickel (NiMn ₂ O _4), the entire reference electrode may be formed of a manganese, nickel, or, A part of the reference electrode may be composed of nickel manganate.

It is explanatory drawing which shows the structure of the gas sensor of Example 1. FIG. It is explanatory drawing which shows the gas sensor used in Experimental example 1. FIG. 6 is a graph showing experimental results of electromotive force for each gas in Experimental Example 1. It is a graph which shows the experimental result (detection electrode reference | standard) of the sensitivity of the gas sensor of Experimental example 2. FIG. It is a graph which shows the experimental result (reference electrode reference | standard) of the sensitivity of the gas sensor of Experimental example 2. FIG. It is a graph which shows the experimental result (reference electrode reference | standard) of the sensitivity of the gas sensor of Experimental example 3. FIG. It is explanatory drawing which shows the gas sensor used in Experimental example 4. 10 is a graph showing experimental results of electromotive force of the gas sensor of Experimental Example 4. 10 is a graph showing experimental results of electromotive force of the gas sensor of Experimental Example 4. 10 is a graph showing experimental results of electromotive force of the gas sensor of Experimental Example 4. 10 is a graph showing experimental results of electromotive force of the gas sensor of Experimental Example 4. It is explanatory drawing which shows the structure of the gas sensor of Example 2. FIG. It is explanatory drawing which shows the structure of the gas sensor of Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 41, 61 ... Gas sensor 3, 43, 63 ... Sensor element 5 ... Temperature control part 7, 53, 73 ... Gas measurement part 9, 45, 65 ... Base | substrate 11, 47, 67 ... Reference electrode 13, 49, 69 ... Detection electrode 21 ... Thermocouple 23 ... Heater 27 ... Digital electrometer 51, 71 ... Heater substrate

Claims (11)

A gas sensor having a sensor element in which at least one pair of electrodes is provided on a substrate having a solid electrolyte as a main component, and detecting the concentration of a predetermined gas in the gas to be measured based on the electrical characteristics between the paired electrodes In
One of the pair of electrodes is a reference electrode containing nickel manganate (NiMn ₂ O ₄ ) , and the other electrode paired with the reference electrode is a detection electrode. . The gas sensor according to claim 1, wherein a potential difference between the reference electrode and the detection electrode is measured, and a concentration of a predetermined gas in the measurement target gas is measured based on the potential difference. The gas sensor according to claim 1 or 2 , wherein the predetermined gas is oxygen gas. The gas sensor according to any one of the claims 1-3, wherein the solid electrolyte characterized in that it is a stabilized zirconia. The gas sensor according to any one of claims 1 to 4 , wherein the detection electrode is an electrode mainly composed of a platinum group or a platinum group alloy. The gas sensor according to any one of claims 1 to 5 , wherein a measurement temperature when measuring the concentration of the gas is 300 to 700 ° C. The gas sensor according to any one of claims 1 to 6 , further comprising a temperature sensor and / or a heater. A gas concentration for detecting a concentration of a predetermined gas in a gas to be measured based on an electrical characteristic between the paired electrodes, using a sensor element in which at least one pair of electrodes is provided on a substrate mainly composed of a solid electrolyte In the measurement method,
A reference electrode containing nickel manganate (NiMn ₂ O ₄ ) is used as one electrode of the pair of electrodes, and a sensing electrode paired with the reference electrode is used as the other electrode. A gas concentration measuring method, wherein the concentration of the predetermined gas is measured by placing the electrode in the measurement gas and bringing the electrodes into contact with the measurement gas. 9. The gas concentration measurement method according to claim 8 , wherein a potential difference between the reference electrode and the detection electrode is measured, and based on the potential difference, a concentration of a predetermined gas in the gas to be measured is measured. . 10. The gas concentration measuring method according to claim 8 , wherein the concentration of the predetermined gas is measured without using a reference gas or a reference gas with respect to the reference electrode. The gas concentration measurement method according to any one of claims 8 to 10 , wherein a measurement temperature for measuring the concentration of the gas is set to 300 to 700 ° C.

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