JPH01245144A - Oxygen ion conductive ceramics film electrode - Google Patents

Abstract

PURPOSE:To enable measurement with good reproducibility and stability immediately even after the long-term interruption of the measurement by providing a high-temp. holding means to the mixture in a film container. CONSTITUTION:A powder mixture 2 is packed into the pressure resistant container 1 formed of an oxygen ion conductive ceramics film having liquid impermeability. An electrode lead wire 3 consisting of an electron conductor, a resistance heater 5 and a temp. sensor 6 are embedded into the powder mixture 2 and the open end is sealed by a sealant 4. The powder mixture 2 is a mixture composed of the particles of a metal and the oxide of this metal or a mixture composed of two kinds of the oxides of the same metal which are different in metal valency. The electrode is constituted in such a manner and the heater 5 and the sensor 6 are used in combination with a power supply and a power supply controller. The potential responds immediately after the restart of the measurement even after the ambient temp. of the film electrode falls over a long period of time even if the powder mixture 2 is maintained in the prescribed measurement temp. range of a high temp. even during the interruption of the high-temp. measurement.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Field of Industrial Application) This invention is applicable to high-temperature water and its solutions in chemical plants, thermal power plants, nuclear power plants, geothermal power plants, and fuel reprocessing plants. P at high temperatures for use in industrial facilities etc. that handle
Regarding the oxygen ion conductive ceramic membrane electrode mainly used for measuring H, in more detail, it is an oxygen ion conductive ceramic membrane electrode that can be used again without loss of reproducibility or stability even after long periods of interruption in high temperature measurements. This invention relates to a membrane electrode.

(Prior Art) Glass electrodes have traditionally been used to measure the pH of aqueous solutions. However, this glass electrode had the drawback that it could not be used at high temperatures.

Therefore, in recent years, oxygen ion conductive ceramic membrane electrodes (Japanese Patent Publication No. 61-22260, L, W) have been developed as pH sensors suitable for measuring pH in aqueous solutions, especially at high temperatures.
, N1edrach: J-E electro
chem.

Soc, 127.2122-2130 (1980) and W, N1edrach & W, H,5to
ddard:Ind, Eng, Chem, pr
od, Res, Dev, .

22.594-599 (1983)') was developed. This membrane electrode is an indicator electrode used for measuring the concentration of a strong acid or a strong base in a solution of a strong acid and water or a strong base and water (Japanese Patent Application Laid-Open No. 60-65037).
Or the electrode body of a reference electrode used for detecting the concentration of acid or base in a solution of base and water (Patent Application No. 61-2)
No. 71766) or supporting electrode (Patent Application No. 1986-27176)
No. 5 and No. 61-271766).

Several types of specific structures of acid-based ion-conductive ceramic membrane electrodes are known, depending on the internal structure of the container made of the ceramic membrane. Each type has a long end, so it is best to choose one depending on the purpose of use. However, the following two types of methods are known as being superior in that it is easy to limit the active region of the membrane electrode.

The first method of oxygen ion conductive ceramic membrane electrode is
It is equipped with the following (a> to (d)).

(a) A container consisting of a fluid-impermeable and pressure-resistant partition wall, in which the entire partition wall or a portion of the partition wall connecting both surfaces of the partition wall is composed of an oxygen ion conductive ceramic piece.

(b) A conductive path for an electrode terminal, which contacts the inner surface of the container of the membrane and extends outside the container, and is made of an electronically conductive material.

(C) A mixture of a metal and an oxide of the metal placed inside the container.

(d) A sealant for insulating the inner surface of the membrane and the mixture from substances and pressure outside the container.

Hereinafter, this type of oxygen ion M conductive ceramic membrane electrode will be referred to as a metal+metal oxide internal electrode type oxygen ion conductive ceramic membrane electrode.

The second method of oxygen ion conductive ceramic membrane electrode is
The above (a>, (b) and (d>) and the following (cl
It is equipped with the following.

(C1 A mixture of two types of oxides of the same metal with different metal valences arranged inside the container.

Hereinafter, this type of oxygen ion conductive ceramic membrane electrode will be referred to as a heterovalent gold 12ii oxide mixture internal electrode type oxygen ion conductive ceramic membrane electrode.

A typical example of the structure of a conventional oxygen ion conductive ceramic membrane electrode realized by these two types of methods is shown in FIG.

As shown in the figure, a mixed powder 2 (described later) is housed in a pressure-resistant container 1 made of a fluid-impermeable oxygen ion conductive ceramic membrane in contact with the inner surface of the container 1, and an electronic An electrode lead wire 3 made of a conductor is embedded in the mixed powder 2 and extended to the outside of the container 1, and a sealing material 4 isolates the inside of the container 1 containing the mixed powder 2 from substances and pressure outside the container. Here, the mixed powder 2 is composed of metal particles and particles of the metal oxide in the case of a metal/metal oxide internal electrode type membrane electrode. In this case, the conductive path for the electrode terminal is
Metal particles in contact with the oxygen ion conductive ceramic membrane, and a large number of metal particles in the mixed powder 2 in contact with each other;
It is formed by an electrode lead wire 3 which is embedded in the mixed powder 2 and is in contact with the metal particles. In addition, in a membrane electrode of a heterovalent metal oxide mixture internal electrode type, the mixed powder 2 is
It consists of at least two types of oxide particles of the same metal with different metal valences. In this case, unless at least one of the oxides is an oxide whose main charge carrier is electrons and which has high conductivity, in addition to the two types of oxide particles mentioned above, platinum particles or gold particles or sufficient Particles of carbon having electrical conductivity are also mixed into the mixed powder 2. In this case, the mixed powder 2 contains one of two types of oxides or platinum, gold, or carbon, which are electronically conductive substances having sufficient electrical conductivity, and the conductive path for the electrode terminal is The particles of the electronically conductive substance in contact with the oxygen ion conductive ceramic membrane and the large number of particles of the electronically conductive substance in the mixed powder 2 that are in contact with each other, and the particles of the electronically conductive substance in the mixed powder 2 are embedded in the mixed powder 2 to improve the electronic conductivity. It is formed by the electrode lead wire 3 in contact with the particles of the sexual substance.

Hereinafter, the oxygen ion conductive ceramic membrane electrode using this configuration will be referred to as the oxygen ion conductive ceramic membrane electrode of the heterovalent gold lff1' hydride mixture internal electrode type.

Incidentally, it is known that oxygen ion conductive ceramic membrane electrodes are suitable for use at high temperatures because they have good potential accuracy at high temperatures. However, in the conventional membrane electrodes of the metal+metal oxide internal electrode type and the heterovalent metal oxide mixture internal electrode type, the present inventor used the Ill electrode to measure pH, etc. at high temperatures (for example, 90°C). When the measurement is interrupted for a long time (e.g. 10 days),
When the measurement is restarted next time, the potential of the membrane electrode will be at a value different from the steady-state potential for a while after restarting, even if the sample liquid composition has not changed over time during the interruption of the measurement. I found something easy to do. In this case, there is a tendency that the longer the interruption time, the slower the speed of return to the steady potential.

Therefore, in industrial facilities that handle high-temperature aqueous solutions, p l
When using conventional membrane electrodes of the metal earth metal oxide internal electrode type and the heterovalent metal oxide internal electrode type for measurements at high temperatures such as −1, e.g. If measurement is to be interrupted for a long time due to inspection or maintenance of a sample liquid container or sampling line, remove the membrane electrode from the installation location each time to avoid the above problem, and install the membrane electrode separately in advance. This poses a problem in that the replacement measurement system that has been placed in storage must be kept in a high-temperature measurement state even during the suspension of the original measurement, which requires complicated handling and requires a complicated replacement device. At this time, if it is difficult to easily reattach after removal, the test liquid may easily leak from the attachment part.

(Problem to be Solved by the Invention) As described above, the conventional oxygen ion conductive ceramic membrane electrodes of the metal 1,000 metal oxide internal electrode type and the heterovalent metal oxide mixture internal electrode type are difficult to measure at high temperatures. If the measurement is interrupted for a long time, it may be difficult to make accurate measurements for a while after the measurement is restarted, or when used for measurements in industrial facilities, complicated handling and complicated equipment are required to prevent such situations. There are problems such as.

The present invention has been made in order to solve the problems of the conventional technology, and its purpose is to enable immediate measurement with good reproducibility and stability even after a long interruption of measurement at high temperatures, and thus What about the complicated handling of removing the membrane electrode and maintaining the high temperature measurement state during measurement interruption? ! It is an object of the present invention to provide an oxygen ion 'rr1 conductive ceramic membrane electrode of a metal earth metal oxide internal electrode type and a heterovalent metal oxide mixture internal electrode type, which eliminates the need for complicated equipment.

[Structure 1 of the Invention (Means for Solving the Problems) The present inventor has proposed a method for long-term measurement using conventional membrane electrodes of the metal+metal oxide internal electrode type and the heterovalent metal oxide mixture internal electrode type. After repeated experimental investigations into the unsteady potential caused by interruption, the above-mentioned II! The unsteady potential of the electrode is determined at a predetermined temperature (
This may occur if the temperature of the membrane electrode drops (for example, 20°C) for a long period of time during use (e.g., 100°C), and some oxygen ion conductive ceramic membrane electrodes with other internal configurations are We found that there are cases where such unsteady potential is not particularly recognized due to interruption, and we have developed a conventional membrane electrode of gold + gold WAM compound internal electrode type or heterovalent metal oxide mixture internal electrode type. The above-mentioned unsteady potential occurs due to the temperature history of a mixture of a metal and an oxide of that metal, or a mixture of only two types of oxides of the same metal with different metal valences, inside the membrane electrode. I realized that it could be considered. Based on these facts, the present inventor has completed an invention having the following configuration that achieves the above object.

That is, the oxygen ion conductive ceramic membrane electrode of the present invention having a metal+metal oxide internal electrode type is composed of (a) a fluid-impermeable and pressure-resistant partition wall, and the entire partition wall or the space between both surfaces of the partition wall is A container in which a portion of the connecting partition wall is made of an oxygen ion conductive ceramic membrane.

(b) A conductive path for an electrode terminal that contacts the inner surface of the container of the membrane and extends to the outside of the container, and is made of an electronically conductive material.

(c) A mixture of a metal and an oxide of the metal, or a mixture of two types of oxides of the same metal with different valences, placed inside the container.

(d) A sealant for insulating the inner surface of the membrane and the mixture from substances and pressure outside the container.

The oxygen ion conductive ceramic membrane electrode comprising the above (a) to (d) is characterized in that it further comprises means for maintaining a high temperature for the mixture.

In the two types of membrane electrodes of the present invention, the high temperature holding means for each mixture can be easily provided on the membrane electrode and does not affect the potential of the membrane electrode depending on the composition of the test liquid. If so, any device can be used, but one that has a resistance heater and a temperature sensor that outputs an electric signal is preferable from the viewpoint of temperature control ability.

In this case, these are used in combination with a power supply for the resistance heater and a power supply controller whose input signal is the electrical signal of the temperature sensor. These power sources and power controllers are preferably installed separately outside the membrane electrode. In that case, the g!
Problems such as removing the m-electrode and maintaining the high temperature measurement state in the substitute measurement system, which require complicated handling and complicated equipment, do not occur.

However, in the voltage measurement path between the terminal of the membrane electrode and the terminal of an electrode (for example, a reference electrode) used in pair with the membrane electrode for measuring f)H, etc., the oxygen ion conductive ceramic Since membranes often have high electrical resistance, they induce noise due to electrostatic induction from an external noise environment, which tends to interfere with the use of membrane electrodes. Therefore, when using it in a place where noise is likely to be induced from the outside,
The voltage measurement path is used with electrostatic shielding from the squared part. In the membrane electrode of the present invention, when the power source is an AC power source, when the electric signal of the temperature sensor is an AC signal, or when the lead wires of the resistance heater and the temperature sensor extend into an external noise environment, As long as the oxygen ion conductive ceramic membrane is present, noise is likely to be induced in the conductive path for the electrode terminal that is electrically connected to it. It is desirable to electrostatically shield the oxygen ion conductive ceramic film and the electrode terminal conductive path from the resistance heater and temperature sensor by separating them with a wall or a net.

(Function) The potential of the membrane electrode is the difference in internal potential from the test liquid in contact with the membrane electrode to the electrode terminal of the membrane electrode. In the oxygen ion conductive ceramic membrane electrodes of the metal+metal oxide internal electrode type and the heterovalent metal oxide mixture internal electrode type, the electrode terminal also serves as the conductive path for the electrode terminal. The potential is determined by the internal potential difference at the interface between the test liquid 1 and the oxygen ion conductive ceramic membrane and the oxygen ion conductive ceramic membrane 1.
It is equal to the sum of the internal potential difference at J3 at the interface of the electronically conductive material (electrode terminal conductive path). The internal structure of the container of the oxygen ion conductive ceramic membrane electrode of the metal soil metal oxide internal electrode type and the heterovalent metal oxide mixture internal electrode type is l! The structure is exactly the same as that of the internal reference electrode of some of the well-known high-temperature oxygen gas sensors using ion-driven ceramics (Japanese Patent Publication No. 61-22260 and J, HIa
dik edition ``Physics of electrolytes or E
lectrolytesJ, (Academicp
J, HIadi in Chapter 20 of (Ress, 1972)
K's paper [Reference ElectrodeReferenceElectro
desJ), the internal potential difference at the interface of the oxygen ion conductive ceramic membrane 1 and the electron conductive material (electrode terminal conductive path) is determined by the oxygen gas partial pressure inside the container of the membrane electrode and the temperature of the interface. However, the oxygen gas partial pressure inside the container is in equilibrium with the combination of a metal and its oxide or the combination of two types of oxides of the same metal with different metal valences in each mixture inside the container. is determined only by the temperature of the mixture, but the reaction between the mixture and the oxidizing gas is generally slow, and the oxygen gas partial pressure does not immediately reach an equilibrium value in response to a sudden change in temperature. If the temperature of the mixture drops for a long time due to interruption of measurement at high temperature, even if the temperature returns to the initial high temperature, the oxygen gas partial pressure inside the container will not immediately reach the equilibrium value determined only by the temperature, and will continue to do so. Therefore, with conventional membrane electrodes, although the internal potential difference at the interface of the test liquid I oxygen ion conductive ceramic membrane gradually reaches a steady value, the potential of the membrane electrode does not reach the steady value immediately. .

However, since the III electrode of the present invention has a means for maintaining a high temperature for the mixture, even if the ambient temperature of the membrane electrode falls below the predetermined measurement temperature range for a long time,
The mixture itself can be easily maintained at a high temperature within a predetermined measurement temperature range. If this is done, 1) the partial pressure of oxygen gas inside the container η remains at the equilibrium value at the temperature within the predetermined measurement temperature range even though the measurement at high temperature is being interrupted; When the measurement of the potential of the membrane electrode is started, the internal potential difference at the interface between the oxygen ion conductive ceramic membrane 1 and the electron conductive material (equal electric path for the electrode terminal) immediately assumes a steady value. Therefore, in the Jl electric potential of the present invention, the electric potential can quickly reach a steady value.

(Example) An example of the present invention is shown in FIG. This has a resistance heater as a high temperature holding means and a temperature sensor that outputs an electric signal, which is suitable in the present invention, and a power supply for the resistance heater and the temperature sensor are provided outside the membrane electrode separately from the membrane electrode. This device is used in combination with a power supply controller that receives an electrical signal as an input signal, and other than the high temperature holding means it has, it is similar to the conventional membrane electrode shown in Figure 4. It has the same structure as the representative structure. In FIG. 1, parts common to the conventional example shown in FIG. 4 are given the same reference numerals.

A mixed powder 2 to be described later is contained in a pressure-resistant container 1 made of a fluid-impermeable oxygen ion conductive ceramic membrane.
It is packed inside the closed end side. An electrode lead wire 3 made of an electronic conductor is embedded in the mixed powder 2 and extends to the outside of the container 1. A resistance heater 5 for roughly heating the mixed powder 2 and a temperature sensor 6 for measuring the temperature of the mixed powder 2 and outputting an electric signal are embedded in the mixed powder 2. The resistance heater 5 is composed of a heating resistor 5a, a lead wire 5b for the heating resistor, a heat-resistant electrically insulating tube 5C covering these, a shielding conductor 5d, and an electrically insulating member m5e.

The temperature sensor 6 also includes a temperature measuring element 6a covered with an electrical insulation coating (not shown), a lead wire 6b for the temperature measurement element covered with an electrical insulation coating (not shown), and an electrostatic shielding conductor 6C covering these. - It is composed of an electrical insulating film 6d. The lead wire portions of the resistance heater 5 and the temperature sensor 6 also extend to the outside of the container 1, similar to the electrode lead FA3. The inside of the container 1 containing the mixed powder 2 is sealed with a sealing material 4 at the open end of the container 1 in order to isolate it from external substances and pressure. Note that, similar to the conventional membrane electrodes of the metal oxide internal electrode type and the heterovalent metal oxide mixture internal electrode type, in the membrane electrode of the present invention, the above-mentioned sealing is performed using Ar, He, which removes oxygen as much as possible. It is preferable to conduct the application in an inert gas such as , N2, etc. Also, in order to securely fix the mixed powder 2, a material such as glass wool, which is inert to the substances in the container 1 and heat resistant, is placed in the space above the mixed powder 2. It may also be filled with a substance.

Here, the mixed powder 2 is similar to that used in the conventional electrode shown in FIG. Become.

Similarly, a V7A type membrane electrode inside a heterovalent metal oxide mixture is composed of particles of at least two different types of metal oxides of the same metal, and at least one of the oxides is the main charge carrier. In addition to particles of the two types of oxides mentioned above, at least the surface is made of platinum, gold, an alloy of platinum and gold, or carbon with sufficient electrical conductivity, unless it is an oxide with electrons and high electrical conductivity. The particles are also mixed together. Further, the electronic conductor used for the electrode lead wire 3 is preferably one whose at least the surface is made of platinum, gold, or an alloy of platinum and gold. The particles may be made of the same metal as the metal particles used in the mixed powder 2.

Note that various materials can be used for the heating resistor 5a, such as a wire or band made of nickel-chromium or iron-chromium, or a nonmetallic heating element such as silicon carbide. Further, a thermoelectric pair, a resistance temperature detector, a thermistor temperature detector, or the like can be used as the temperature measuring element 6a. Furthermore, the power source of the resistance heater 5 used in combination with the membrane electrode is a DC power source, the electric signal of the temperature sensor 6 is a DC signal, and the resistance heater 5
The lead wire portion of the temperature sensor 6 transmits noise caused by electrostatic induction to the container 1 made of an oxygen ion conductive ceramic film and the electronically conductive substance in the mixed powder 2 in contact with it via the resistance heater 5 and the temperature sensor 6. If the electrical insulating film 5e is arranged in an environment where it is difficult to induce the electrode lead wire 3,
6d and the electrostatic shielding conductors 5d and 6c can also be omitted.

Therefore, the resistance heater 5 and the temperature sensor 6 can be electrically isolated from other parts of the membrane electrode by using a suitable resistance heater power supply and a power supply controller that takes the electrical signal of the temperature sensor 6 as an input signal. In this state, it is possible to maintain the mixed powder 2 at a predetermined high temperature without inducing noise due to electrostatic induction from the outside into the electronically conductive material in the container 1 and the mixed powder 2 and the electrode lead wire 3. It functions as a high temperature maintenance means.

The present invention is not limited to the above-mentioned embodiments, and the high-temperature holding means can be easily provided on the membrane electrode and can influence the potential of the m-electrode depending on the composition of the sample liquid. If not, the pj! It may also be provided on the electrode.

Furthermore, if there is no problem in attaching and removing the membrane electrode to the installation location and it can be handled as one with other parts of the membrane electrode,
The high temperature holding means may be attached to the outside of the container of the membrane electrode.

In addition, the part of the membrane electrode other than the high-temperature holding means may be of the metal earth metal oxide internal electrode type or the heterovalent metal oxide mixture internal electrode type, as long as the high-temperature holding means can be easily installed. Among the conventional membrane electrodes shown in FIG. 4, those having structures other than those shown in FIG. 4 may be used. As long as the container of the membrane electrode has a structure consisting of a fluid-impermeable and pressure-resistant partition wall, the partition wall does not need to be entirely composed of an oxygen ion conductive ceramic membrane. As long as an oxygen ion conductive ceramic membrane can connect both surfaces of the partition wall, and the electrical resistance of the membrane in the thickness direction is sufficiently smaller than the input resistance of the potentiometer used to measure the potential of the membrane electrode, a part of the partition wall Furthermore, the shape and dimensions of the container can be made appropriate depending on the purpose of use, as long as the high temperature maintaining means can be easily installed.

Next, we will discuss the reproducibility and stability of the potential at the point where high-temperature measurement resumes after a long period of low temperature holding due to interruption of high-temperature measurement in membrane electrodes of metal + metal oxide internal electrode type and heterovalent metal oxide mixture internal electrode type. The effect of having a high temperature holding means on the performance will be explained based on experimental data.

Regarding each of the metal+metal oxide internal electrode type and the heterovalent metal oxide mixture internal electrode type membrane electrode, the structure shown in FIG. 1 was used as an example of the present invention, and a comparative example using a conventional membrane electrode was used. The structure shown in Fig. 4 was manufactured using the configuration described below.

That is, the container 1 is a 4.5 ffio l/Y203 stabilized zirconia tube in the shape of a Tammann tube with each membrane electrode having a length of 220 mm, an inner diameter of 25 mm, and an outer diameter of 28 IllIII. In the membrane electrode of the example, in the resistance heater 5, a commercially available silicone rubber coated heating cable is passed through a steel wire braided shield taken out from a commercially available coaxial cable together with the lead wire portion, and this is roughly coated with PTFEil.
The temperature sensor 7 is made of a commercially available metal sheath with aluminum foil wrapped around the lead wire (insulating coating) in advance, including the part that contacts the lead wire of the metal sheath. A platinum-filled resistance thermometer was used with one end sealed and inserted into a PTFE tube. Mixed powder 2 contains 300 meshes each of A(] + A(] in a weight ratio of 4:1 for the metal + metal oxide inner electrode type membrane electrode).
20 mixed powders, and for the heterovalent metal oxide mixture internal electrode type membrane electrode, 300 powders each in a weight ratio of 1:1:1.
A mixed powder of mesh Fe3O4 + α-Fe 203 +Pt was used to fill each container 1 to a depth of 150 ral. The electrode lead wire 3 has a length of 2001 m+1. Using one Pt wire with a diameter of 11 Im, it was placed in the mixed powder 2 at a depth of 10
It is inserted to 0mm. For each membrane electrode, sealing material 4
was formed using a commercially available heat-resistant epoxy resin adhesive, and sealing was performed in an argon gas purged glove box.

Next, prepare two multi-neck flasks with double capacity, one multi-neck flask has a metal soil metal oxide internal electrode type, and the other multi-neck flask has a heterovalent metal oxide mixture internal electrode type. of,
One membrane electrode of each example and comparative example was attached using an O-ring manufactured by Piton. Each multi-necked flask was further equipped with one commercially available high-temperature saturated calomel electrode, one platinum resistance thermometer in a metal sheath with a lined wire shielded to the outside of the shield case (described later), and a reflux condenser. An oxalate pH standard buffer defined by JIS K8474 was filled as a test solution.

Each of the multi-necked flasks was placed in separate mantle heaters whose lead wires were shielded with aluminum foil, and each mantle heater was placed in the same shield case. The single wire portion of each of the resistance heater 5 and temperature sensor 6 provided in the membrane electrode of each example is connected to an electrostatic shielding conductor 5d made of a copper wire braided shield and an electrostatic shielding conductor 6C made of an aluminum foil. In a state where the outside of the shield case was shielded, it was connected to a slider and a temperature controller installed outside the shield case, so that the temperature of the mixed powder 2 in the membrane electrode of the example could be controlled by these. The temperature of the test liquid is determined by a mantle heater, a platinum resistance thermometer installed in a multi-necked flask and immersed in the test liquid, and a separate slider and temperature controller installed outside the shield case. This made it possible to control it. The potential of each membrane electrode is determined by comparing it with the saturated calomel electrode installed in the flask with the same diameter.
I made it possible to measure using a 4Ω home-made electrometer.

The following experiment was conducted using the above apparatus. First, the temperature of each test liquid was controlled at 80° C., and continuous immersion was performed until all membrane electrodes reached a steady potential (permissible fluctuation range ±0.5 mV). After confirming that the steady potential of all the membrane electrodes had been reached, the potential measurement was interrupted, and all the membrane electrodes were immediately taken out from each multi-necked flask and held in air at room temperature for a predetermined period of time by suspending them by respective lead wires. During this time, each g! The temperature of the mixed powder 2 in the membrane electrode was controlled at 80°C. Immediately after the completion of holding for a predetermined period of time, each membrane electrode was reinstalled in the original flask with each row in which the temperature of the test liquid was maintained at 80° C., and potential measurement was restarted. Such an experiment was first conducted for a predetermined time of 1 hour, and then for a predetermined time of 30 days. After restarting the measurement, the amount of change over time in the potential of the membrane electrodes of Examples and Comparative Examples from the steady potential before holding at the highest temperature is shown in the second column for the metal→metal oxide internal electrode type membrane electrode.
In the figure, the internal electrode type of different valent metal oxide is shown in FIG. From these figures, it can be seen that with conventional membrane electrodes, both the metal-ten-metal oxide internal electrode type membrane electrode and the heterovalent metal oxide mixture internal electrode type membrane electrode, the potential returns to the original potential quickly after resuming measurement. However, in the membrane electrode of the example equipped with a high temperature holding means, the potential is not particularly affected by the holding time at room temperature during measurement interruption. It was found that it responded immediately and had good reproducibility and stability.

In addition to achieving the object of the present invention related to interruption of measurement, the membrane 'i\X electrode of the present invention also has a function of maintaining a high temperature of the test liquid during measurement or an auxiliary heating function. Depending on the thermal conditions of the liquid, etc., it is possible to utilize this function as appropriate.

[Effects of the Invention] In the oxygen ion conductive ceramic membrane electrodes of the present invention, which are of the metal ten metal oxide internal electrode type and the heterovalent metal oxide mixture internal electrode type, measurement at high temperatures is interrupted and the ambient temperature of the membrane electrode is reduced. Even if the temperature drops below the specified measurement temperature range for a long time,
Unlike conventional membrane electrodes, it does not become difficult to make accurate measurements immediately after resuming measurement as the ambient temperature drops, nor does recovery become slow. The potential responds immediately and has good reproducibility and stability.

This has a great influence on the reproducibility and stability of the potential of the 119 i-electrode, and at the partial pressure of oxygen gas inside the container whose equilibrium is determined by the reaction of the membrane electrode with the mixture inside the container, the temperature Despite the fact that reaching the equilibrium partial pressure depending on This is because the temperature can be easily maintained within a high temperature predetermined measurement temperature range.

Therefore, in industrial facilities that handle high-temperature aqueous solutions, rlH
Or, when used to measure acid/base concentration, etc., it eliminates the need for complicated handling such as pulsing, removing membrane electrodes, and maintaining high temperature measurement conditions during long interruptions in measurement. Become.

Therefore, even if it is difficult to easily reinstall the device after removal and the test liquid is likely to leak from the attachment portion due to removal, it can be used without any problem.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of one embodiment of this invention, and Figure 2 is a metal +
A graph showing changes over time in the potential of membrane electrodes according to Examples and Comparative Examples with metal oxide internal electrode type membrane electrodes. Figure 3 is an example of a heterovalent metal oxide mixture internal electrode type membrane electrode. and a graph showing the change over time in the membrane M electrode potential according to the comparative example,
FIG. 4 is a sectional view of a conventional example. 1... Container 2... Mixed powder 3... Lead wire 4... Sealing material 5... Resistance heater 6... Temperature sensor

Claims (1)

[Scope of Claims] A container comprising a fluid-impermeable and pressure-resistant partition wall, the entire partition wall or a portion of the partition wall connecting both surfaces of the partition wall being formed of an oxygen ion conductive ceramic membrane; a conductive path for an electrode terminal that is in contact with the inner surface of the membrane container and extends outside the container, and is made of an electronically conductive material; and a mixture of a metal and an oxide of the metal, or An oxygen ion conductor comprising: a mixture of two types of oxides of the same metal having different metal valences; and a sealing material for insulating the inner surface of the container of the membrane and the mixture from substances and pressure outside the container. What is claimed is: 1. An oxygen ion conductive ceramic membrane electrode, further comprising means for maintaining the mixture at a high temperature. (2) The oxygen ion conductive ceramic membrane electrode according to claim 1, wherein the high temperature holding means includes a resistance heater and a temperature sensor that outputs an electric signal. (3) The oxygen ion conductive ceramic film and the electrode terminal conductive path are electrostatically shielded from the resistance heater and the temperature sensor.
The oxygen ion conductive ceramic membrane electrode described above.