JP2023004737A - Solid electrolyte sensor use method and solid electrolyte sensor - Google Patents

Abstract

To provide a solid electrolyte sensor with which, when using zirconia-containing platinum wire as a lead wire on at least a measurement atmosphere side, it is possible to connect the zirconia-containing platinum wire to an electrode with a high level of adhesion.SOLUTION: Provided is a solid electrolyte sensor 1 comprising a first electrode 21 and a second electrode 22 respectively provided in a first space S1 and a second space S2 defined by a sensor element 10 which is formed from a solid electrolyte, the solid electrolyte sensor measuring, via a first lead wire 41 and a second lead wire 42, the electromotive force generated between the first electrode 21 and the second electrode 22 due to ion conduction in the sensor element 10. At least the first lead wire 41 is a zirconia-containing platinum wire which is a wire formed from platinum that contains zirconia, with a pure metal platinum wire 45 wound round the sensor element 10 from above the first lead wire 41 laid along the first electrode 21.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a method of using a solid electrolyte sensor and a solid electrolyte sensor used according to the method of use.

Various solid electrolyte sensors have been proposed that detect the concentration of gases such as hydrogen gas, oxygen gas, carbon dioxide gas, and water vapor using solid electrolytes (ion-conductive ceramics) as sensor elements. are proposing. These solid electrolyte sensors use the principle of a concentration cell in which a difference in concentration of the same ion causes a potential difference in the solid electrolyte. Measure the electromotive force generated in the sensor element. Of the two spaces, if the concentration of the gas to be detected in the first space is known, the gas concentration in the second space can be known from the measured electromotive force and the temperature of the sensor element using the Nernst equation. can. Alternatively, while the gas concentration in the first space is constant, the electromotive force is measured while the gas concentration in the second space is changed, and the correlation is investigated in advance. From the measured value of the electromotive force, the gas concentration in the second space can be known.

When measuring the electromotive force generated by ion conduction, an electrode is provided on the surface of the sensor element that is in contact with one of the two spaces, and an electrode is also provided on the surface that is in contact with the other space. A wire is connected to the electrometer. Generally, a platinum electrode is used as the electrode and a platinum wire is used as the lead wire.

However, if the measurement atmosphere is a high-temperature atmosphere such as in an industrial furnace, the platinum wire used as the lead wire may break. If the lead wire is broken, the electromotive force cannot be measured, so it is necessary to remove the solid electrolyte sensor from the industrial furnace and repair it. Therefore, even if other parts of the solid electrolyte sensor are normal, the service life during which the electromotive force can be normally measured is shortened only by the disconnection of the lead wire.

Therefore, the present applicant has proposed using a zirconia-containing platinum wire, which is a wire made of platinum containing zirconia, at least as a lead wire on the measurement atmosphere side (see Patent Document 1). Platinum containing zirconia has high creep rupture strength at high temperatures, so it is a material that has been conventionally used for furnaces and crucibles for melting glass, bushings for manufacturing glass fibers, etc. By using platinum containing zirconia, which has been used as a structural material, as a wire material (zirconia-containing platinum wire), it is possible to obtain a lead wire that does not easily break even at high temperatures. In addition, even if a zirconia-containing platinum wire is used as a lead wire, it is possible to detect the electromotive force generated by ion conduction without any problem, as in the case of the conventional solid electrolyte sensor in which the lead wire is a platinum wire.

However, the lead wire, which is a zirconia-containing platinum wire, has a problem that it is difficult to connect to the electrode due to its high adhesion.

Japanese Patent Application Laid-Open No. 2021-43061

Therefore, in view of the above circumstances, the present invention provides a method for using a solid electrolyte sensor that can connect a zirconia-containing platinum wire to an electrode with high adhesion when using a zirconia-containing platinum wire at least as a lead wire on the measurement atmosphere side. and to provide a solid electrolyte sensor used according to the method of use.

In order to solve the above problems, a method of using a solid electrolyte sensor according to the present invention (hereinafter sometimes simply referred to as "method of use") is as follows:
"A sensor element formed of a solid electrolyte, a first electrode provided on the surface of the sensor element, and a second space separated from the first space in contact with the first electrode, the surface of the sensor element A method of using a solid electrolyte sensor comprising a second electrode provided in
The atmosphere of the first space is the atmosphere to be measured,
Of the first lead wire connected to the first electrode and the second lead wire connected to the second electrode, at least the first lead wire is a wire made of platinum containing zirconia. Using platinum wire containing zirconia,
An electromotive force generated between the first electrode and the second electrode due to ion conduction in the sensor element is measured via the first lead wire and the second lead wire,
A pure metal platinum wire is wound around the sensor element from above the first lead wire along the first electrode.

In this method of use, of the two spaces (first space and second space) partitioned by the sensor element, the atmosphere in the first space is used as the measurement atmosphere, and the first electrode connected to the first electrode in the first space is used as the measurement atmosphere. A zirconia-containing platinum wire, which is a wire made of platinum containing zirconia, is used as the lead wire. Zirconia-containing platinum wires have higher creep rupture strength at high temperatures than pure metal platinum wires, which have been widely used as lead wires, so they are less likely to break even in a high-temperature measurement atmosphere. Moreover, when the members constituting the sensor thermally expand at high temperature, a large tensile force is applied to the lead wire, and this is considered to be one of the main causes of breakage of the lead wire at high temperature. On the other hand, since the zirconia-containing platinum wire has high tensile strength at high temperatures, it is difficult to break even when a large tensile force is applied. Therefore, even if the measurement atmosphere is a high-temperature atmosphere, the sensor element can be used for a long service life in which disconnection of the lead wire is suppressed, and ion conduction according to the concentration difference between the first space and the second space of the detection target gas. It is possible to measure the electromotive force generated in

However, it is difficult to bend, wind, or twist the zirconia-containing platinum wire so as to adhere to the shape of the sensor element. This is thought to be because the inclusion of zirconia, which is a ceramic, reduces the ductility peculiar to metals, revealing the properties of ceramics, which is a brittle material. Therefore, in the present invention, a pure metal platinum wire is wound around the sensor element from above the first lead wire, which is a platinum wire containing zirconia, along the first electrode, which is the electrode on the measurement atmosphere side. Since the pure metal platinum wire has excellent malleability, it can be wound tightly around the sensor element, and the first lead wire can be pressed against the first electrode to be in close contact. That is, the first lead wire, which is a zirconia-containing platinum wire that is difficult to adhere to the first electrode by itself, can be connected to the first electrode with high adhesion.

In addition, since zirconia is an electrically insulating ceramic, when a zirconia-containing platinum wire and a pure metal platinum wire are brought into contact, the electrical contact is the same as the contact between platinum wires, and the first electrode and It does not affect the measurement of the electromotive force generated between the second electrode.

The method of using the solid electrolyte sensor according to the present invention includes, in addition to the above configuration,
"By applying a platinum mesh through which the first lead wire is passed to the first electrode, the first lead wire is laid along the first electrode, and the first lead wire passed through the platinum mesh The platinum wire is wound around the sensor element from above."

In this configuration, the first lead wire is passed through the mesh of the platinum mesh, the platinum mesh is applied to the first electrode, and the pure metal platinum wire is wound around the sensor element. As a result, the platinum mesh electrically connected to the first lead wire comes into contact with the first electrode, and this state is firmly held by the platinum wire wound around the sensor element. The connection via the platinum mesh is added to the electrical connection between the first electrode and the first lead wire. Electrical connection becomes more reliable and good. Moreover, since the first lead wire is passed through the platinum mesh, it is suppressed that the platinum mesh is displaced and detached from the first electrode.

Next, the solid electrolyte sensor according to the present invention is
"A sensor element formed of a solid electrolyte, a first electrode provided on the surface of the sensor element, and a second space separated from the first space in contact with the first electrode, the surface of the sensor element and the first lead wire connected to the first electrode and the first lead wire connected to the first electrode and the A solid electrolyte sensor for measuring via a second lead connected to a second electrode, comprising:
Of the first lead wire and the second lead wire, at least the first lead wire is a zirconia-containing platinum wire that is a wire made of platinum containing zirconia,
A pure metal platinum wire is wound around the sensor element from above the first lead wire along the first electrode.

Further, the solid electrolyte sensor according to the present invention, in addition to the above configuration,
"The first lead wire is passed along the first electrode by applying the platinum mesh through which the first lead wire is passed to the first electrode, and the first lead passed through the platinum mesh The platinum wire is wound around the sensor element from above the wire."

These are solid electrolyte sensor configurations used in accordance with the methods of use described above. By using the atmosphere of the first space as the measurement atmosphere, the above effects are exhibited.

As described above, according to the present invention, when using a zirconia-containing platinum wire at least as a lead wire on the measurement atmosphere side, a method of using a solid electrolyte sensor that can connect the zirconia-containing platinum wire to an electrode with high adhesion, And a solid electrolyte sensor used by the method of use can be provided.

FIG. 1(a) is a side view of the essential part of the solid electrolyte sensor according to the first embodiment of the present invention, and FIG. 1(b) is a vertical cross-sectional view of the same portion as FIG. 1(a). FIG. 2(a) is a side view of essential parts of a solid electrolyte sensor according to a second embodiment of the present invention, and FIG. 2(b) is a partially enlarged longitudinal sectional view of the same part as in FIG. 2(a).

A method of using a solid electrolyte sensor according to an embodiment of the present invention and solid electrolyte sensors 1 and 2 used in this method of use will be described below with reference to the drawings.

In the solid electrolyte sensor 1 of the first embodiment, a first space S1 and a second space S2 are separated by a sensor element 10 made of a solid electrolyte. As shown in (b), two spaces are separated by holding the sensor element 10 in the holder 30 . Specifically, by fixing the sensor element 10 to one end of the cylindrical holder 30 via the sealing material 39, the holder 30 and the sensor element 10 are combined to form a bottomed cylindrical shape. , divided into two spaces. The holder 30 is made of a material having electrical insulation and heat resistance, such as alumina ceramics or mullite ceramics.

Here, the shape of the sensor element 10 is cylindrical with a bottom, and the case where the inside of the holder 30 is open is exemplified.

In the fixed electrolyte sensor 1, either of the bottomed cylindrical inner space and the outer space may be the first space S1, which is the atmosphere to be measured. Here, the bottomed cylindrical outer space is the first space S1. . When a hole is provided in the furnace wall of an industrial furnace and a fixed electrolyte sensor is inserted into the hole to measure the gas concentration in the atmosphere inside the furnace, the bottomed cylindrical external space is used as the first space S1. becomes.

A first electrode 21 is provided on the surface of the sensor element 10 on the side of the first space S1, and a second electrode 22 is provided on the surface on the side of the second space S2. A first lead wire 41 is connected to the first electrode 21 and a second lead wire 42 is connected to the second electrode 22 . By connecting the first lead wire 41 and the second lead wire 42 to an electrometer (not shown), the electromotive force generated between the first electrode 21 and the second electrode 22 is detected.

Platinum electrodes are used as the first electrode 21 and the second electrode 22 . The platinum electrode is a porous film formed by applying a platinum paste for electrode to the surface of the sensor element 10 and baking it.

A thermocouple 51 for detecting the temperature of the sensor element 10 is inserted in the second space S2. Each is inserted through one of a plurality of holes axially penetrating through. Furthermore, an introduction pipe 60 for introducing the reference gas is inserted into the second space S2. The reference gas is a gas whose detection target gas concentration is known, but the atmosphere may be used as the reference gas in some cases. In that case, the second space S2 may be open to the atmosphere without inserting the introduction pipe.

In this embodiment, a pure metal platinum wire (0.3 mm in diameter) is used as the second lead wire 42 , and a zirconia-containing platinum wire (0.3 mm in diameter) is used as the first lead wire 41 . The zirconia-containing platinum wire is a wire made of platinum in which 0.4% by mass of zirconia (zirconium dioxide) is dispersed. The zirconia content in the zirconia-containing platinum wire is preferably in the range of at least 0.3% by mass to 0.5% by mass, since it does not interfere with electrical conductivity.

The first lead wire 41 runs along the surface of the tip of the sensor element 10 so as to pass through the portion where the first electrode 21 is formed, and then extends to the end of the holder 30 on the sensor element 10 side. It extends along the surface of the holder 30 toward the other end and is connected to an electrometer.

A platinum wire 45 (diameter 0.3 mm) is wound around the sensor element 10 a plurality of times at a portion where the first lead wire 41 is along the first electrode 21, and both ends of the platinum wire 45 are wound around the sensor element 10. are twisted together. Since the pure metal platinum wire 45 has excellent malleability, it can be tightly wound around the sensor element 10, and the tightly wound state can be maintained by twisting both ends. Since the zirconia-containing platinum wire is difficult to deform, if the first lead wire 41 is simply placed along the first electrode 21, a gap is likely to occur between the two and the mutual contact is likely to be insufficient. Since the platinum wire 45 is tightly wound around the sensor element 10 from above 41, the electrical connection between the first lead wire 41 and the first electrode 21 is good.

In addition, since the zirconia-containing platinum wire has lower ductility than the pure metal platinum wire, even if the first lead wire 41 itself is wound around the sensor element 10 at the portion where the first electrode 21 is formed, It cannot be wrapped tightly, and if one tries to twist the ends together after wrapping, it will break when twisted. It is considered that this is because the brittle nature appears due to the inclusion of zirconia, which is a ceramic, in platinum.

When the solid electrolyte sensor 1 having the above configuration was actually installed in an industrial furnace and used to detect the gas concentration in a measurement atmosphere at a temperature of 600°C, it was confirmed that the first lead wire 41 could be used for a long period of time without disconnection. was done.

Further, using the solid electrolyte sensor 1 of the present embodiment, the reference gas is introduced into the second space S2, while the concentration of the target gas to be detected is changed stepwise and supplied to the first space S1. The electromotive force was measured when For comparison, a solid electrolyte sensor identical to the solid electrolyte sensor 1 except that a pure metal platinum wire was used as the first lead wire 41 was similarly introduced into the second space S2 with a reference gas. On the other hand, the electromotive force was measured when the first space S1 was supplied with a gas in which the concentration of the gas to be detected was varied stepwise.

The results are similar to those reported in US Pat. The value of is in good agreement with the theoretical value calculated using the Nernst equation, confirming that the electromotive force associated with ion conduction in the solid electrolyte can be measured without problems.

Next, the solid electrolyte sensor 2 of the second embodiment will be described with reference to FIGS. 2(a) and 2(b). The solid electrolyte sensor 2 differs from the solid electrolyte sensor 1 of the first embodiment in that a platinum mesh 47 is used to electrically connect the first lead wire 41 to the first electrode 21 . Specifically, the first lead wire 41 is passed through the platinum mesh 47, and the platinum wire 45 is passed over the first lead wire 41 and the platinum mesh 47 while the platinum mesh 47 is applied to the first electrode 21. It is wound around the sensor element 10 multiple times. Both ends of the platinum wire 45 are twisted together in the same manner as in the solid electrolyte sensor 1 . The first lead wire 41, which is a zirconia-containing platinum wire, is hard to bend, but by bending the platinum mesh 47, the first lead wire 41 can be passed through the mesh of the mesh.

As the platinum mesh 47, it is preferable that the platinum wires constituting the mesh are thin and flexible, and that the number of meshes is large so that the number of intersections of the platinum wires serving as electrical contacts is large. For example, a platinum wire having a diameter of 0.076 mm and a platinum mesh of 80 mesh can be used.

In the solid electrolyte sensor 2 , the platinum wire 45 wound around the sensor element 10 firmly holds the platinum mesh 47 electrically connected to the first lead wire 41 in contact with the first electrode 21 . The connection through the platinum mesh 47 is added to the electrical connection between the first electrode 21 and the first lead wire 41, and the intersections of the platinum wires that constitute the platinum mesh 47 are electrical contacts, and many Because of its presence, the electrical connection is more reliable and better. In addition, since the first lead wire 41 is passed through the platinum mesh 47 , the platinum mesh 47 is prevented from being displaced and detached from the first electrode 21 .

As described above, according to the solid electrolyte sensors 1 and 2 of the present embodiment, the first lead wire 41 arranged in the first space S1, which is the measurement atmosphere, is a zirconia-containing platinum wire, so that the measurement atmosphere can be kept at a high temperature. However, the breakage of the lead wire can be suppressed, and the electromotive force generated in the solid electrolyte due to ion conduction can be normally measured over a long period of time. The zirconia-containing platinum wire has low ductility, and it is difficult to wind the first lead wire 41 itself around the sensor element 10 or to twist the ends together. Just by putting them together, a gap is likely to occur between them and the mutual contact tends to be insufficient, but by winding the platinum wire 45 from the top of the first lead wire 41, good electrical connection is achieved. be able to.

In the solid electrolyte sensor 2, since the first lead wire 41 and the first electrode 21 are electrically connected through the platinum mesh 47, the number of electrical contacts is increased and the electrical connection is more reliable. it will be good.

As described above, the present invention has been described with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and as shown below, various improvements can be made without departing from the scope of the present invention. and design changes are possible.

For example, in the above embodiment, of the first lead wire 41 and the second lead wire 42, only the first lead wire 41 arranged in the first space S1 which is the measurement atmosphere is the zirconia-containing platinum wire, and the second lead wire Although the wire 42 is exemplified as a pure metal platinum wire, the second lead wire 42 can also be a zirconia-containing platinum wire.

The solid electrolyte sensor 1 is an example in which the bottomed cylindrical sensor element 10 is fixed to the holder 30 in such a direction as to open inside the holder 30 , but the bottomed cylindrical sensor element 10 opens outside the holder 30 . It may be directed to Further, the shape of the sensor element fixed to one end of the tubular holder is not limited to the bottomed tubular shape, and may be columnar or disk-shaped.

Furthermore, two spaces are also separated by fixing the sensor element in the middle of the cylindrical holder via a sealing material. In this case, the combined shape of the holder and the sensor element has two bottomed cylindrical portions, so there is no concept of distinguishing between the internal space and the external space, but one is defined as the first space S1. Let the other be the second space S2. The shape of the sensor element fixed in the middle of the holder can be columnar, disk-shaped, or cylindrical with a bottom.

Further, in the above description, the case where the two spaces are separated by forming the combined shape of the holder and the sensor element into a bottomed cylinder is exemplified. A solid electrolyte sensor in which two spaces are separated by only the sensor element can also be obtained by forming the sensor element into a shape.

In addition, in the solid electrolyte sensors 1 and 2, after applying the platinum paste so that the platinum wire 45 wound around the sensor element 10 is embedded, heat treatment may be performed at a temperature of 800.degree. C. to 1000.degree. As a result, in the solid electrolyte sensor 1, the first lead wire 41, the platinum wire 45, and the first electrode 21 are integrated with the solidified platinum paste. better connection. Moreover, in the solid electrolyte sensor 2, the first lead wire 41, the platinum wire 45, the platinum mesh 47, and the first electrode 21 are integrated with the solidified platinum paste. better electrical connection. As the platinum paste, a platinum paste for electrode formation can be used.

1 solid electrolyte sensor 2 solid electrolyte sensor 10 sensor element 21 first electrode 22 second electrode 30 holder 41 first lead wire 42 second lead wire 45 platinum wire 47 platinum mesh S1 first space S2 second space

Claims (4)

a sensor element formed of a solid electrolyte, a first electrode provided on the surface of the sensor element, and a second space separated from the first space in contact with the first electrode, on the surface of the sensor element A method of using a solid electrolyte sensor with a second electrode provided, comprising:
The atmosphere of the first space is the atmosphere to be measured,
Of the first lead wire connected to the first electrode and the second lead wire connected to the second electrode, at least the first lead wire is a wire made of platinum containing zirconia. Using platinum wire containing zirconia,
An electromotive force generated between the first electrode and the second electrode due to ion conduction in the sensor element is measured via the first lead wire and the second lead wire,
A method of using a solid electrolyte sensor, wherein a pure metal platinum wire is wound around the sensor element from above the first lead wire along the first electrode. By applying a platinum mesh through which the first lead wire is passed to the first electrode, the first lead wire is arranged along the first electrode and above the first lead wire passed through the platinum mesh 2. A method of using a solid electrolyte sensor according to claim 1, wherein said platinum wire is wound around said sensor element from a thin film. a sensor element formed of a solid electrolyte, a first electrode provided on the surface of the sensor element, and a second space separated from the first space in contact with the first electrode, on the surface of the sensor element a first lead wire connected to the first electrode and the second A solid electrolyte sensor for measuring via a second lead connected to two electrodes, comprising:
Of the first lead wire and the second lead wire, at least the first lead wire is a zirconia-containing platinum wire that is a wire made of platinum containing zirconia,
A solid electrolyte sensor, wherein a pure metal platinum wire is wound around the sensor element from above the first lead wire along the first electrode. The first lead wire is passed along the first electrode by applying a platinum mesh through which the first lead wire is passed to the first electrode, and the first lead wire is passed through the platinum mesh. 2. A method of using a solid electrolyte sensor according to claim 1, wherein said platinum wire is wound around said sensor element from above.

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