JPH01291151A - Oxygen sensor - Google Patents

Abstract

PURPOSE:To measure the concn. of oxygen with high accuracy without requiring a detecting electrode and reference electrode by using a specific triple defect type perovskite structure. CONSTITUTION:For example, oxide, carbonate, etc., are weighed, in accordance with stoichiometric compsn. and are mixed and ground, then the powder mixture is precalcined for about 12 hours at 800-930 deg.C, for example, about 900 deg.C. After the powder is sufficiently ground, an org. solvent and binder are added thereto and the mixture is made into paste. A thick film is formed of such paste on a substrate. Further, electrode paste is baked on the thick film to form electrodes. The paste is thereafter calcined for about 5 hours at 800-930 deg.C, for example, about 900 deg.C and the sensor element of the triple defect perovskite structure A2BCu3O7-delta (where A denotes at least one member of the element in a group consisting of Ba, Sr, Ca; B denotes at least one member of the element in a group consisting of Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, and Yb; delta denotes a non-stoichiometric parameter) is obtd. The measurement with the high accuracy is thus enabled.

Description

[Detailed description of the invention] [Industrial application field]

The present invention utilizes the characteristics of triple-defect structure perovskite, whose conductivity changes with changes in oxygen concentration in the atmosphere,
This invention relates to an oxygen sensor for detecting oxygen in gas or measuring oxygen concentration.

[Background of the invention]

Oxygen sensors include those made of solid electrolytes such as stabilized zirconia that utilize ionic conductivity, and those made of oxide semiconductors such as titanium oxide that utilize the semiconductivity of oxides. . Among these, the former solid electrolyte oxygen sensor forms an oxygen concentration battery and generates an electromotive force when there is a difference in oxygen partial pressure on both sides of the solid electrolyte. This makes it possible to know the oxygen partial pressure on both sides. Furthermore, the resistance value of the oxide semiconductor oxygen sensor changes with changes in the partial pressure of oxygen in the gas atmosphere. It was designed to take advantage of the fact that As this oxide semiconductor type oxygen sensor, an oxygen sensor using a perovskite type oxide semiconductor has been proposed (Japanese Patent Laid-Open No. 62-30945, Japanese Patent Publication No. 62-39383).
(No. Publication). By the way, an oxygen sensor using a solid electrolyte requires a detection electrode and a reference electrode, which must be completely separated, which has the drawback of complicating the film construction and increasing the size. There is also the problem that the M plan partial pressure on the reference pole side must be known. On the other hand, oxide semiconductors whose main composition is titanium oxide do not have the above problems, but the firing temperature is 110°C.
Because the temperature is over 0℃! Expensive platinum must be used as the electrode material, and if inexpensive silver, copper, nickel, etc. are used, the electrodes must be baked after firing the element. Another problem is that it is necessary to support platinum as a catalyst for reacting oxygen with titanium oxide. In addition, oxygen sensors using Perodisky 1-type oxide semiconductors have a high electrical resistance value unless the temperature is higher than 600°C, and measurement accuracy decreases at lower temperatures, and in extreme cases, measurement may become impossible. It ends up.

[Disclosure of the invention]

The present invention aims to provide an oxygen sensor that does not require both a sensing electrode and a reference electrode. Another object of the present invention is to provide an oxygen sensor that has high measurement accuracy and is capable of measuring even in a relatively low temperature range of about 400°C. Another object of the present invention is to provide an oxygen sensor in which electrodes can be provided at the same time as the element is sintered, and base metals can be used as electrode materials. Another object of the present invention is to provide an oxygen sensor that does not require a catalyst to be supported on the element. The present invention was made to achieve the above-mentioned object, and it is a triple-defected lobskite structure ^zl)CusO.
t-δ (where A represents at least one member of the group consisting of a, Sr, and Ca, and B represents Y, La, N
cl, Sm, Eu, Gd, Dy, lo, Er,
δ represents at least one member of the group consisting of Tii, Yb, and δ represents a non-chemotypic parameter. The non-chemotypic parameter δ is preferably 0 to 1, more preferably It is desirable that the value is about 0.3 to l.Also, the triple defect in the present invention has a lobskite structure^z
BcuiOt-δ is, for example, 1la2Ycu*Oy-
Not only the type of δ (, [1aSrYCu30v−δ
, or flag-ysryYcu30y-δ (where y is a number from 0 to 2). The oxygen sensor element having the triple-defect lobskite structure is adjusted as follows. For example, weigh oxides, carbonates, etc. based on their stoichiometric composition.
, mixed and pulverized at 800-930°C, for example about 90°C.
Calcinate at 0°C for about 12 hours. Next, after thoroughly pulverizing this, an organic solvent and a binder are added to make it into a paste, and a thick film is formed on the substrate. create. Furthermore, an electrode paste is baked on this thick film to form an electrode. Thereafter, 1 to 1
If fired for 0 hours, for example about 5 hours, the triple-defect perovskite structure of the present invention ^JCu30t-δ (however, A
represents at least one member of the group consisting of Da, Sr, and Ca, and B represents Y, La, Nd, Sm, Eu, and G.
d, Dy, llo, E", represents at least one member of the group consisting of T-1yb, and δ represents a non-chemical theoretical parameter). This oxygen sensor element is composed of The sintered body exhibits an xa diffraction pattern as shown in Figure 1, and has a triple-defected lobskite type (^) crystal structure as shown in Figure 2.
tBculOy−δ), and the amount of oxygen in the crystal changes depending on the oxygen partial pressure of the atmosphere. And when this material is used as an oxygen sensor, 400
The relationship between the specific resistivity and oxygen partial pressure of this oxygen sensor element at 500°C and 500°C is shown in Figure 3. It's a very similar relationship. Furthermore, it can be seen that measurement is possible even in a relatively low temperature region of about 400° C., and that it exhibits an effective effect as an oxygen sensor element.

[Example 1] BaCO3, Y, 01, and CuO were used as raw materials, which were weighed, mixed, and pulverized to a chemical composition, and heated to 900°C for 12
Calcined for an hour. After pulverizing this, an organic solvent and a binder are added to form a base 1~, which is then formed as a thick film on a substrate. A silver electrode paste was applied onto this thick film to form an electrode, and the paste was fired at 900° C. for 5 hours. When this was used as an oxygen sensor element and its resistivity was measured in atmospheres having various oxygen partial pressures, the results shown in FIG. 3 were obtained, indicating that it could be applied as an oxygen sensor. (Examples 2 to 6) Using carbonate and oxide as raw materials, l1aSrYCu307-δ, BaCaYCusO
y-δ, B az L 11 Cu s Ot-δ,
Ba2GdCu, Oy-δ, [1alYbCusL-
δ. An oxygen sensor element was obtained. Regarding this oxygen sensor element, we measured the resistance value when the temperature was 400°C and the oxygen partial pressure in the atmosphere was 10'Pa and the resistance value at 10'Pa, and calculated the ratio.The results are shown in Table 1.
It was shown to. Table-1 ・Resistance at Po*”IO’(Pa)/PotJO’(P
Resistance and measurement temperature at a) (400°C) The results showed that each of the samples had sufficient performance to be used as an oxygen sensor at 400°C.

【effect】

As explained in detail above, the oxygen sensor of the present invention includes:
High measurement accuracy (,400
It has the advantages of being able to perform measurements at relatively low temperatures of about ℃, applying electrodes at the same time as sintering the device, allowing the use of base metals as electrode materials, and eliminating the need for catalysts to be supported in the device.

[Brief explanation of the drawing]

Figure 1 shows the x & 1 diffraction pattern of BazYCu30t-δ fired at 900°C, Figure 2 is an illustration of the triple-defect lobskite structure, and Figure 3 shows the relationship between resistivity and oxygen partial pressure of Da2YCu-Oy-δ. This is a graph showing. Patent applicant Chichibu Cement Co., Ltd. - 1 page engraving 2θ (&) Fig. 1 Log (PO2/PO) Fig. 3 ○ 0 (kLJ (Uranus 1421.oo) Fig. 2 Procedures Amendment Book 1986 9 2nd day of the month

Claims (1)

[Claims] Triple defect perovskite structure A_2BCu_3O_
7_-δ (However, A represents at least one member of the group consisting of Ba, Sr, Ca, and B represents Y, La, Nd, S
m, Eu, Gd, Dy, Ho, Er, Tm, Yb, and δ represents a non-stoichiometric parameter.