JPS6275249A - Ph electrode for high-temperature water - Google Patents

Abstract

PURPOSE:To obtain an electrode which has low internal impedance and can make simple and quick measurement of the high-temp. water at a very small point by providing a semiconductor which is stable in the hight-temp. water the 1st conductor terminal which is disposed in contact therewith and is set at the specified potential and the 2nd and 3rd conductor terminals which are disposed in contact with said semiconductor. CONSTITUTION:The pH electrode 10 is made into the construction having the n-type semiconductor 1 which consists of TiO2, the 1st conductor terminal 21 which is disposed in contact therewith and is set at the specified potential, the 2nd and 3rd conductor terminals 22, 23 which are disposed in contact with the semiconductor 1 and detect the resistance change thereof and a hydrogen sensitive layer 5 which contacts with the surface of the semiconductor 1 and consists of Pd insulated from the terminals 21-23 via a thin Al2O3 film 4. The sensor part of such pH electrode 10 is immersed in the high-temp. water and the terminal 21 is set at the specified potential, then the resistance value is changed by the hydrogen ions taken by the semiconductor 1 from the layer 5. The resistance value correlating with the pH value is obtd. by measuring such change between the terminals 22 and 23.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electrode for measuring pt-+ in a minute portion of high-temperature, high-pressure water in a boiling water reactor or the like.

[Technical background of the invention and its problems]

Conventionally, P has been used as an electrode for measuring high temperature water pH.
T-hydrogen electrodes, Pd-hydrogen compound electrodes, or solid electrolyte diaphragm-type electrodes are being considered, and T i 02 semiconductor sensors are also being investigated. However, each of these electrodes has drawbacks, such as: Requires hydrogen injection, Short lifespan, High internal impedance and slow response, and Troublesome measurement. Unfortunately, no electrodes have been developed that can accurately measure pH in minute areas such as gaps over long periods of time.

[Purpose of the invention]

The present invention aims to provide an electrode that has low internal impedance and can easily and quickly measure high-temperature water at minute locations.

[Summary of the invention]

The present invention includes a semiconductor that is stable in high-temperature water, a first conductor terminal placed in contact with the semiconductor and set to a constant potential, and a resistance change of the semiconductor placed in contact with the semiconductor. It is characterized by comprising second and third conductor terminals.

According to the present invention, as described above, it is possible to obtain an electrode that has a low internal impedance and can easily and quickly measure high-temperature water at a minute location.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1(A> and 1B).

First, TiO2 single crystal (rutile structure, C-axis length direction)
Cut a material with a radius of 25M and a length of 2m from
．． After puff polishing with alumina particles of 0.05 μm, ultrasonic cleaning was performed in alcohol. Next, the degree of vacuum is 10-'t
The n-type semiconductor 1 was fabricated by performing thermal doping for 5 hours in an atmosphere at a temperature of 1200°C. After etching this semiconductor 1 in concentrated sulfuric acid at 150°C for 1 hour,
Using a masking material (not shown) on part of the three side surfaces, β films were deposited at equal distances from each other for ohmic junction by CVD using aluminum acetate as a deposition source. Continuing, AQ paste was applied on each Aλ film, and the first to
After forming the third conductor terminals 21 to 23, each conductor terminal 2
Pt lead wires 3 were connected to terminals 1 to 23. Next, the surface of the semiconductor 1 except for the conductor terminals 21 to 23 is covered with a masking material (not shown), and the surface of the semiconductor 1 is coated with a Fi 500A (7) AQ by CVD method.
A 2O3 thin film 4 was formed on each conductor terminal 21-23. Note that the thicknesses of the six theories were determined by measuring them with an ebsometer. After the formation of AQ2Q31pi44, a Pd film with a thickness of 1000 nm is vacuum-deposited on the entire surface of the semiconductor 1 including the Al22O3 thin PIA4 to form a hydrogen sensitive layer 5.
The sensor part of the electrode was prepared by forming the following.

Finally, the lower part of the semiconductor 1 of the sensor section is placed on the stepped part of the end face of the fluororesin tube 8 via the fluororesin backings 6a, 6b and the Rulon backing 7, and the fluororesin cap 9 is placed on the outer circumference of the tube 8. high temperature water pH electrode 1 fixed with said tube 8 and cap 9 by screwing onto the surface;
0. Figure 1 (A>, (B) shown).

The high temperature water pH electrode 10 of the present invention is shown in FIGS. An n-type semiconductor 1 made of TiO2, a first conductor terminal 21 placed in contact with the semiconductor 1 and set to a constant potential, and a resistance change of the semiconductor placed in contact with the semiconductor 1. Second and third conductor terminals 2 to be detected
2.23 and each conductor terminal 2 in contact with the surface of the semiconductor 1
The hydrogen sensitive layer 5 made of Pd is insulated from the hydrogen sensitive layer 1 to 23 via A22OiillL$.

When the sensor part of the high-temperature water pH electrode 10 having such a configuration is immersed in high-temperature water and the first conductor terminal 21 is set to a constant potential, the semiconductor 1 becomes resistant due to the hydrogen ions taken in from the hydrogen-sensitive layer 5. The value changes, and by measuring this tag between the second and third conductor terminals 22, 23, it is possible to determine the resistance value that correlates to pH1llI. This will be explained with reference to the energy band diagram of FIG. In FIG. 2, the sensor section including the hydrogen-sensitive layer 5 of the electrode 10 is immersed in a solution, and a system in which a constant voltage is applied is expressed as energy (E
). In the figure, ΔΦH is the potential difference in the Helmholtz layer, and ΔΦSC is the potential difference in the space charge layer.

Now, if the potential from the first conductor terminal 21 applied to the semiconductor 1 is controlled to be constant with respect to the reference electrode, the following equation holds true.

E Erc(=ΔΦ8c−ΔΦ, (= consta
nt If the hydrogen ion concentration of the solution increases, ΔΦH increases accordingly, and ΔΦs satisfies the above equation.
c also increases. In terms of current A, this increases the thickness of the space charge layer and theoretically decreases the carrier concentration, which corresponds to an increase in the resistance of the semiconductor 1 itself. Therefore, by measuring this change in resistance between the second and third conductor terminals 22 and 23 placed in contact with the semiconductor 1, the resistance 1 that determines <l)H is determined as described above. be able to. In such resistance measurement, it is important that ΔΦ) changes sensitively in response to pH changes, and for this reason, in this embodiment, a hydrogen sensitive layer 5 is provided on the surface of the semiconductor 1.

Next, an example of measuring the pH of high-temperature water using the I)H electrode of the present invention will be described with reference to the pH measuring device shown in FIG.

Reference numeral 11 in FIG. 3 is an Au container housed in an autoclave (not shown), and a mixed solution 12 of, for example, Na2SO4+H23O+ is accommodated in the container 11. An insulating support 13 is inserted into the opening of the bead 11. This support 13 has a pH electrode 1 of the present invention.
Reference electrodes 14 made of KCR71)1 of 0 and AQ/AQCff/(0,1 mol/n) are inserted so that their lower portions are immersed in the mixed solution 12. P connected to the first conductor terminal 21 of the pH electrode 10
The t-line 3 is grounded and set at a constant potential.

A voltmeter 15 and an ammeter 1 are connected between the Pt wire 3.3 connected to the second and third conductor terminals 22.23 of the DH electrode 10.
6 is interposed. Further, the reference electrode 14 is grounded via a variable DC power supply 17.

In an apparatus having such a configuration, the voltage of the variable DC power supply 17 is varied to polarize (bias voltage applied) the H electrode 10 using the reference electrode 14, and the mixed solution 12 in the beer force 11 is heated to 290°C by an autoclave. setting and changing the pH Hla of the second and third conductor terminals 22.
The change in resistance value appearing on the PT wire 3.3 connected to 23 was measured using a voltmeter 15 and an ammeter 16. In addition, the H value was actually measured for a similar mixed solution (set at 290°C). When the measured pH values of mixed solutions having different pHs of 11fl were plotted on the horizontal axis and the resistance values measured by the measuring device were plotted on the vertical axis, the characteristic diagram shown in FIG. 4 was obtained. Note that Ra shown on the vertical axis is the resistance value when DH=14. As is clear from the characteristic diagram shown in FIG. 4, when the bias potential (variable DC current gi17) is small (Ve=
○) is l) When the H is low, the measurement point deviates from the straight line, and when the bias potential is large (Vs = 0.4V), the measurement point deviates from the straight line on the high pH side, but for other cases. It is drawn as a straight line in the pH range. Therefore, by using the characteristic diagram shown in FIG. 4 as a calibration curve and comparing the resistance value determined by the H measuring device shown in FIG. 3 with FIG. 4,
I) Hla of high temperature water can be easily measured. Furthermore, by selecting the bias potential, it is possible to perform good pH measurement even for solutions with small changes in resistance that correlate with pH.

Note that although TiO2 was used as the semiconductor in the above embodiment, the present invention is not limited to this. For example, Fe2O+, Cr2O
3, Ni○, 5rTi○3, Zn-0, FeTiO3,
CLI○, C'dO, WO3, CdS, MO82, I
nP, Ge, Si, GaAs, MO8e, Se, S
iC.

The semiconductor may be formed from LaRhO2, V2OS, CdFe2O4, or the like.

In the above embodiment, the hydrogen-sensitive layer is made of Pd, but the hydrogen-sensitive layer may be made of Ta2O5 or Affi2OB.

In the above embodiment, the hydrogen-sensitive layer was arranged in contact with the surface of the semiconductor, but the semiconductor such as TiO2 or Fe2O itself is sensitive to hydrogen ions and the potential difference (ΔΦH) of the Helmholt layer according to the above formula changes. If , the hydrogen sensitive layer can be omitted.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a high-temperature water DHIi electrode that has low internal impedance and can easily and quickly measure high-temperature water at minute locations.

[Brief explanation of drawings]

FIG. 1(A) is a front view of a 1)-H electrode showing an embodiment of the present invention, FIG. An energy band diagram for explaining the action of 1i, Figure 3 is a pH diagram incorporating the l)H electrode of the present invention.
31,11 Schematic diagram showing the determination device, Figure 4 is the actual measured I)
FIG. 2 is a characteristic diagram showing the relationship between Hlli and the resistance value measured by a device having an H electrode. DESCRIPTION OF SYMBOLS 1... Semiconductor made of TiO2, 21-23... Conductor terminal, 3... PT wire, 5... Hydrogen sensitive layer made of Pd, 8... Fluororesin tube, 9... Fluorine Resin cap, 10...l) H electrode, 11...Be force,
12... Mixed solution, 14... Reference electrode, 15...
Voltmeter, 16... Ammeter, 17... Variable DC power supply. Applicant's representative Patent attorney Takehiko Suzue (A) Figure 1 Figure 2 Objection

Claims (5)

[Claims] (1) A semiconductor that is stable in high-temperature water, a first conductor terminal placed in contact with the semiconductor and set to a constant potential, and a change in resistance of the semiconductor placed in contact with the semiconductor is detected. A high temperature water pH electrode comprising second and third conductor terminals. (2) High temperature water pH according to claim 1, characterized in that the semiconductor is TiO_2, Fe_2O_3
electrode. (3) The high-temperature water pH according to claim 1, wherein the first to third conductor terminals are in ohmic contact with the semiconductor through at least one metal of In and Al. electrode. (4) The high temperature water pH electrode according to claim 1, characterized in that a hydrogen sensitive layer is provided on the surface of the semiconductor. (5), the hydrogen sensitive layer is Pd, Ta_2O_5 or Al_
Claim 4, characterized in that it consists of 2O_3.
High-temperature water pH electrode as described in section.