JPS5832153A - Oxygen sensor - Google Patents

Abstract

PURPOSE:To make the action possible even in <=500 deg.C comparatively low temperature ranges, by using a metallic oxide complex consisting essentialy of oxides of lanthanum, bismuth and cobalt. CONSTITUTION:A metallic oxide complex serving as an oxygen sensor element consists essentially of oxides of lanthanum, bismuth and cobalt. It is desirable that the component ratio of each atom is fixed in the range that 0.1-10g atom lanthanum and 0.1-15g atom bismuth per 1g atom cobalt are present and also, the ratio of the sum of each g valence of lanthanum and bismuth to that of cobalt is desirable to be 0.2-15 and moreover, the ratio of g valence of bismuth to that of lanthanum is disirable to be 0.1-10. This metallic oxide compound has an oxygen ion conductive property and at the same time, has an electron conductive property and the electrically conductive property is varied with the variation of partial pressure of oxygen atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is capable of detecting 11 items in gas or determining the degree of purity, etc. This is related to the jlk sensor.

Conventionally, as an oxygen sensor for detecting the concentration of h-wires contained in a gas, a solid electrolyte made of zirconium oxide having oxygen ion conductivity has been mainly used as an element. Concentration battery type batteries have been put into practical use. However, this type of sensor has a complex structure and uses a porous material made of platinum, a noble metal, as an electrode.

There are problems with adhesion with the electrolyte and economical problems such as high cost, and there is a desire for an inexpensive alternative sensor. In addition, zirconium chloride-based oxygen sensors have the disadvantage that the operating temperature is generally around 700'C, and that they cannot be used at temperatures below SOO°C. One object of the present invention is to provide an oxygen sensor that can operate even in the relatively low 111g4 range below SOO°C, which conventional oxygen sensors could not detect.

Another object of the present invention is to use a metal oxide composite mainly composed of oxides of bismuth and cobalt, which is ranked No. 1 among solid electrolytes having a mixed conductivity of oxygen sensor on conductivity and ionic conductivity, which is cheaper. It was found that this can be achieved by using it as a cable sensor element.

tKVC1 Please provide a more detailed explanation of the present invention5.
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The gold III@oxide complex mainly composed of lanthanum, bismuth and cobalt oxides used in the present invention is 49
It has so-called high mixed conductivity, which has excellent oxygen ion conductivity and excellent electronic conductivity at high temperatures, and also has so-called Pal semiconductivity, in which the conductivity changes depending on the oxygen partial pressure in the atmosphere. This was revealed by the present inventors.

According to the present invention, the oxygen partial pressure in the atmosphere is detected or measured by utilizing the excellent mixed conductivity of a metal oxide complex mainly composed of oxides of lanthanum, bismuth, and cobalt. That is possible. In other words, 1. For example, when the oxygen partial pressure in the atmosphere increases, the conductivity of the composite oxide increases accordingly, and the electrical resistance decreases. can do.

The metal oxide complex that is the element of the oxygen sensor in the present invention is mainly composed of oxides of uranium, bismuth, and cobalt, and the composition ratio of each atom is that of copal.
Lanthanum has Ql~ioy atoms, preferably (L2~51i Jlil, children, particularly preferably 0
．． 4JI atoms to 2Is, Bismuth is Q, 1~1! ijl
Atsuko, preferably 12 to 10 Jil atoms, % (a range of L25 to sy atoms is suitable. Furthermore, If of lanthanum and bismuth relative to the number of 9 atoms of cobalt
The ratio of the sum of g-numbers 0 is a2 to 1s, preferably α3 to 10
Further, the ratio of the number of nine atoms of bismuth to the number of Ii atoms of lanthanum is preferably in the range of α1 to ]0, preferably α2 to 8.

The metal oxide composite mainly composed of oxides of lanthanum, bismuth and cobalt according to the present invention.

It has oxygen ion conductivity, electronic conductivity, and usually P-type semiconductivity, and as mentioned above, it has the characteristic that its conductivity changes according to changes in the oxygen partial pressure of the atmosphere. . As long as such properties are not impaired, small amounts of additives may be added for the purpose of improving responsiveness, sensitivity, stability, reproducibility, mechanical strength, and life span.

The form of the metal oxide complex is not particularly limited (but this is due to its good sensitivity and responsiveness and its excellent stability over time), but it is generally pellet-shaped. Preferable forms include a sintered body, a thin film or a thick film, and the like.

There are various methods for forming the metal oxide composite into a pellet-like sintered body. Compounds that can be converted into tread compounds by calcination, such as oxides such as lanthanum oxide, bismuth oxide, cobalt mide, or preferably nitrates.

Although it is a sulfate, other inorganic salts such as Ka@salt and phosphate,
Organic acid salts such as acetates and succinates, chlorides, bromides, W
There is a method of mixing halogenides such as hydrogen oxides, hydroxides, and oxyhalides in a desired ratio and firing the mixture.

Further, the mixed aqueous solution of each of the metal salts described above is hydrolyzed with an alkaline aqueous solution such as 7 mmoni7 water,
It may be prepared by a so-called coprecipitation method and then fired. Furthermore, methods such as creasing and firing a mixture or alloy of the respective metals may be mentioned. The firing temperature for obtaining these sintered bodies is 400 to 1400"c, preferably 40"c.
A range of 0-1300°C is suitable.

As a so-called film-forming method for forming the metal oxide complex into a film, for example, a film may be formed by mechanical processing such as cutting or polishing a solid material such as a pellet or sheet; The material may be pressed or made into a paste, coated on a suitable support and sintered.

In addition, vacuum evaporation method, acetylene spraying method, plasma jet method 1 reactive snow (tsutaring method).

Film forming methods include chemical vapor deposition (C, V, N method), chemical spray method, and oxidation of 9 alloy plating.

The method for detecting the presence or absence or concentration of element #/j using the sensor of the present invention requires that the element be used as a constant source! This can be done by a general method of determining the change in resistance value while maintaining fK. For example, there are methods such as passing a constant value current through the element and detecting changes in electrical resistance with a voltage recorder, or detecting changes in resistance using a variable resistor and a galvanometer using a Wheatstone bridge circuit. An appropriate detection method can be used depending on convenience and usage.

Thus, the present invention provides an oxygen gas sensor that operates at lower temperatures, is easier to prepare, and has various economically advantageous features than conventional sensors.

Hereinafter, the present invention will be explained in detail with reference to Examples.
I am not determined. In the examples, parts are parts by weight, and the rate of change is as shown in 1. It is defined by Formula II and represents the performance as an oxygen sensor element.

Ri - Resistance value in air [Ω] Examples 1 to IL 429 parts of lanthanum oxide (Lgen 03), fermented bisma X (
Bi! O,)9. II 0 parts, cobalt acetate t238
1I was mixed well in a mortar and decomposed at 600°C for 30 minutes. The mixture was thoroughly mixed in a mortar, molded at a pressure of 2 sokg/cd, and fired at 940'c for 6 hours. Crush and mix again in a mortar, mold at a pressure of ]0 Okj/cIi, and heat at 910°C for 4
Bake for an hour.

The thus obtained sintered body (composition LaqnBltnCOe, +40+, s) of a gold-14-fermented VA compound mainly composed of oxides of lanthanum, bismuth, and cobalt was α
5■, Width Om% Length 12.0■ [Apply silver paste to both ends, dry it, sandwich it between silver plate electrodes, and put it in a glass tube with an inner diameter of 20 m with a gas inlet and a gas outlet at each end. and insert the glass tube into an electric furnace. Thus, with the sintered body set in an electric furnace, the resistance values were measured at temperatures ranging from 500°C to 300°C and under two types of atmospheres: air and argon gas with a severe cumulative concentration of 0.2°C and 111°C. (impedance) was determined using the AC bridge method. The results are shown in Table 1.

Table 1 Example 4~IL Lanthanum oxide (Let Os L Bismuth chloride (Bl)
Sintering of metal oxide composites mainly composed of oxides of lanthanum, bismuth, and cobalt having various compositions using predetermined amounts of each of *Os ) and cobalt acetate in the same manner as in Example 1. I adjusted my body. Further, using the sintered body of K, the same method as in Example 1 was carried out in air and in Al.
The resistance values in the argon atmosphere were kept constant.

The results are summarized in Table 2.

No. 212 Procedural Amendment Written October 21, 1980 Mr. Commissioner of the Japan Patent Office 1, Indication of the case Patent Application No. 1983-129399 2, Name of the invention Oxygen sensor 3, Person making the amendment Relationship to the case Patent applicant Higashi, Osaka City 1-11 Minamihonmachi, Ward (300) Teijin Ltd. Representative Tomoo Tokusue 5 Subject of amendment (1) Item 2jl of the specification Correct it as mixed conductivity 1.

(2) "Semiconductivity 1" on page 3, line 6 and page 4, line 14 of the specification is corrected to "semiconductor property 1."

(3) "The composite oxide" on page 3, lines 13 to 14 of the specification is corrected to 1-plated metal oxide composite J.

(4) Insert the following sentence between lines 7 and 8 on page 1s7 of the specification.

[The temperature at which the oxygen sensor of the present invention is used is preferably such that the change in resistance value due to the change in oxygen acidity in the atmosphere is large. Therefore, the temperature is usually in the range of zoo to 700°C, preferably 300 to 600°C. #Temperature is 7
If it is higher than 00°C, the change in resistance value due to the change in oxygen concentration in the atmosphere will be small, which is undesirable, and -1
If the temperature is lower than 200° C., it takes a long time to show a resistance value corresponding to the oxygen concentration in the atmosphere, which is not preferable because the responsiveness of the sensor becomes poor. J (5) The unit of specific resistance in Table 2 on page 10 of the specification, ``Ωcyn-' J, is corrected to ``Ω(''.

that's all

Claims (1)

[Claims] An oxygen sensor characterized in that a metal oxide composite mainly composed of oxides of lanthanum, bismuth, and co-oxide is used as an oxygen sensor element.