JPH02183151A - Ph sensor - Google Patents

Abstract

PURPOSE:To enable application ideally in a wide temperature range from a low temperature near a room temperature to a high temperature exceeding 500 deg.C by forming an ion conducting layer tight on a charge transfer layer to have a solid electrolyte film mainly composed of Bi2O3. CONSTITUTION:An ion conducting layer 2 is formed as film on the surface of a base electrode 1 made of a copper wire at one end part thereof by CVD, sputtering, ion plating or the like. A measuring side electrode comprising Pt or the like is bonded on the surface of the conducting layer 2, which 2 is made up of a lamination of two solid electrolyte films 2a and 2b. One electrolyte film 2a comprised Sb2O3-Bi2O3 and the other electrolyte film 2b comprised WO3-Bi2O3. An oxide film 1a made of an oxide Cu2O of an electrode ground metal is formed between the electrode 1 and the conducting layer 2 and a charge transfer layer 1' is made up of the oxide film 1a and a ground layer of the electrode 1. This enables highly accurate detection of pH in a wide temperature range from a room temperature to a high temperature exceeding 500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a PH sensor that utilizes concentration cell action.

(Prior Art) Conventional PH sensors of this type include an ion conductive layer made of yttria-stabilized zirconia (hereinafter referred to as "YSZJ") on a charge transfer layer formed of a metal conductor and an oxide film of the base metal. A structure is known in which the ion conductive layer is formed in close contact with each other so that the pH can be measured based on the potential difference generated between both surfaces of the ion conductive layer.

[Problem to be solved by the invention]

However, such conventional sensors have extremely low accuracy in low temperature ranges, and cannot be used at all, especially in temperature ranges around room temperature. For this reason, it has only been put to practical use in a high temperature range of 500°C or higher, and cannot be used in a wide temperature range. This is considered to be because, as shown in FIG. 4, the ionic conductivity of ysz is extremely low in the low temperature region up to 500° C., and therefore the ion diffusion rate is extremely slow.

Additionally, in order to improve the response speed, it is desirable to make the 787 layer thinner, but if this is done, the 782 layer will be more likely to peel off due to the difference in linear expansion coefficient with the metal conductor, resulting in a significant decrease in durability. . Therefore, the 787 layer cannot be made thinner, and there is a problem that the response is inevitably inferior.

The present invention solves the problems with conventional sensors and provides a PH sensor that can be suitably used in a wide temperature range from low temperatures near room temperature to high temperatures of 500'C or more, and has excellent responsiveness and durability. The purpose is to provide the following.

[Means to solve the problem]

The PH sensor of the present invention that solves this problem has an ion conductive layer formed by stacking different types of solid electrolyte membranes on a charge transfer layer formed of a metal conductor and an oxide film of the base metal. Each solid electrolyte membrane has Bi2O as its main component.

Specifically, each solid electrolyte membrane has B i 20. 5b
20. , Ce, O□, TeO2, Ta205°N b
206. It is composed of a solid electrolyte material in which one or more kinds of oxide ceramics such as W Oat M n Oz are dissolved in solid solution. The solid solution amount of oxide ceramic is 2 to 10 mo
It is preferable to set it to 1%. The ion conductive layer is CV
D. It is formed by sputtering, ion blating, etc., but the layer thickness is preferably 0.01 to 50 μm. The number of laminated solid electrolyte membranes constituting the ion conductive layer depends on the PH measurement conditions, etc. It is set appropriately.

[Effect]

A solid electrolyte material whose main component is Bi2O.

For example, 5b2o3-Bi203 has high ionic conductivity over a wide temperature range from room temperature to 800°C, as shown in FIG. That is, even the ionic conductivity near room temperature is approximately the same as the ionic conductivity of YSz at 500 to 600°C. Such properties are Bi2O,
The same applies when the oxide ceramic other than 5b2o3 is dissolved in solid solution. Therefore, by composing the ion conductive layer with a material containing B12o3 as the main component, it can be used in a high temperature range of 500°C or higher, and
Even in the low temperature range below C, especially in the low temperature range around room temperature, P
H can be detected with high accuracy.

Further, since the ion conductive layer is formed by laminating different types of solid electrolyte membranes, a thermal expansion coefficient gradient is generated, and the ion conductive layer is sufficiently adapted to the base metal. Therefore, it is possible to both reduce the thickness of the ion conductive layer and prevent it from peeling off, thereby improving responsiveness and durability.

Moreover, non-stoichiometric multi-component oxides between different oxide films,
In other words, since an oxide with many oxygen defects is generated, further improvement in ionic conductivity is expected.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In the PH sensor of this embodiment, as shown in FIG. 1, CVD,
An ion conductive layer 2 is coated and formed by sputtering, ion blasting, or the like. Although not shown, the surface of the ion conductive layer 2 is coated with PT as well as the known ones.
The measurement side electrode consisting of etc. is glued.

As shown in FIG. 2, the ion conductive layer 2 is formed by laminating two types of solid electrolytes [2a and 2b]. Lamination thickness is 0.0f
~50 μm. One solid electrolyte membrane 2a has 5
b203-Bi203, the other solid electrolyte membrane 2
b consists of WO3Big03. 5 for Bi2O3
The solid solution amount of b2o and WO3 is 2 to 10 mo1%, respectively.
It is said that

Between the base electrode 1 and the ion conductive layer 2, an oxide film 1a made of oxide Cu2o of the electrode base metal is formed, and this oxide film 1a and the base layer of the electrode 1 form the charge transfer layer 1.
' is formed.

【Effect of the invention〕

As is clear from the above description, according to the present invention, the PH sensor is capable of accurately detecting PH in a wide temperature range from room temperature to high temperatures of 500°C or higher, and has excellent responsiveness and durability. can be provided.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main part showing one embodiment of the PH sensor according to the present invention, Fig. 2 is an enlarged view of a part thereof, and Fig. 3 is a 5b
20. -Bi20. FIG. 4 is a characteristic curve diagram showing the relationship between ionic conductivity and temperature in YSZ. FIG. 4 is a characteristic curve diagram showing the relationship between ionic conductivity and temperature in YSZ. 1... Electrode base (metal conductor), 1'... Charge transfer layer. 1a... Oxide film, 2... Ion conductive layer. 2a. b...Solid electrolyte membrane. Figure 3 Temperature (6C) Figure 2 Figure 4 η℃ Temperature ('C)

Claims (1)

[Claims] An ion conductive layer formed by stacking different types of solid electrolyte membranes is closely formed on a charge transfer layer formed of a metal conductor and an oxide film of its base metal, and each solid electrolyte membrane has a Bi_2
A PH sensor characterized by containing O_3 as a main component.