JPS5819873A - Leak prevention of oxygen-gas concentration cell - Google Patents

Abstract

PURPOSE:To increse the electric insulation between the current collecting platinum leads of an oxygen-gas concentration cell, and prevent any leak between the said leads by providing high-resistance zirconia layers, which contain large amounts of Y2O3 and the like, between the said leads and a base zirconia electrolyte. CONSTITUTION:Raw sheets 1 and 1a are formed from zirconia powder stabilized with Y2O3, an organic binder and a plasticizer. Next, a paint prepared by dissolving stabilized zirconia and containing 18-50mol% of a rare-earth-element oxide such as CaO or Y2O3, is applied to both surfaces of the raw sheet 1 before the paint is dried so as to form electric insulating layers 2 and 2a. Next, current collecting platinum leads 3 and 3a are formed on the layers 2 and 2a by printing, and the raw sheet 1a is superposed over the sheet 1 so that a fine platinum wire 4 is buried between the sheets 1 and 1a. After that, they are joined together by heating and pressing, and the joined body is sontered by being subjected to binder eliminating treatment, thereby obtaining a base plate for an oxygen-gas concentration cell. By the means mentioned above, stable leak-preventing layers can be formed between the leads 3 and 3a without deteriorating the airtightness and the thermal shock characteristic.

Description

[Detailed Description of the Invention] This invention relates to a method for preventing leakage between the current collector IJ + )1 of an oxygen gas concentration battery using a zirconia solid electrolyte @ Oxygen gas concentration battery using zirconia as a solid electrolyte It is widely used in fuel cells, industrial measurement and control as a wide oxygen concentration meter, and automobile exhaust gas control.

Conventionally, various attempts have been made to increase the circuit voltage by connecting these oxygen gas concentration batteries in series. For example, a unit cell is constructed by attaching a negative electrode (fuel electrode) 11 to the inner surface of a cylindrical zirconia electrolyte and attaching a positive electrode (air electrode) to the outer surface.
By connecting these cells in series in a comb shape, or by partially forming a plurality of single cells on a porous support ceramic substrate by chemical vapor deposition (CVD), Derazu I spraying, etc., the negative electrode and the zirconia There are methods such as forming the electrolyte and the positive electrode in that order, and then connecting these cells with an interconnector, but these methods have the disadvantages that the process is complicated, it is difficult to ensure reliability, and the cost is high. In order to improve this point, we created a Zilphere raw sheet containing thermoplastic resin as a binder, and formed negative and positive electrodes and glue for series connection on both sides of the sheet by screen printing. There is a method of heat-pressing this to create a hollow part of the tube, and then sintering it at high temperature to create an oxygen gas concentration battery, but this method involves arranging cells with different potentials on the same Zirnia thin plate. However, there is a drawback that the cells cannot be spaced close to each other to prevent leakage between them, and
Connection-V? There was also a drawback that the two sides of the zirconia thin plate could not be crossed.

Particularly when used in an automobile exhaust gas sensor, it is desirable to deposit one end of the sensor into the exhaust gas through the insertion hole, with the opening on the air electrode side facing the outside, and the output signal v-ymYr being taken out from this part. Due to necessity)
There was a problem in that the output voltage -y and the series-connected cells V of each unit cell could not be avoided in close proximity to each other or crossed each other, resulting in a decrease in the output voltage due to leakage.

In order to improve all of the above-mentioned conventional drawbacks, this invention forms a layer with the same crystal structure and component elements as the base zirconia electrolyte, but with a different composition ratio, at the location where leak prevention is required. - The aim is to make it possible to manufacture oxygen gas concentration batteries with low output power loss without compromising quality, chemical or mechanical stability.

In addition, Figure 1 shows the process t-70- of manufacturing a cylindrical oxygen gas concentration battery using a raw sheet of zirconia solid electrolyte.
It is a figure explained with a chart. Generally, zirconia (Zr
Om) Solid electrolyzed poor ore, CaO1YtOs as a stabilizer for cubic crystals to prevent embrittlement due to crystal transformation from tetragonal to monoclinic system, and as a semiconducting agent to simultaneously generate oxygen ion vacancies. Or Gd Tomi Os, Y
4 to 16 moles of rare earth element oxides such as
It is manufactured by mixing moj)% with Zr(h and calcining them to form a solid solution.To explain the case of stabilizing with YmOs, the amount of YmOs dissolved in the solid solution depends on the mechanical performance. The difference depends on whether you place importance on electrical performance or electrical performance. If you place emphasis on mechanical performance, use a partially stabilized product with 6 to 8 mol% solid solution and some monoclinic crystals remaining. If performance is important, use a solid solution with a maximum conductivity of around 10 mol%.The conductivity at 0800°C is 6.
IXIO-2g-c in mol% solid solution and 1.5xlO-''g-1/- in 10 mol% solid solution.

Using the zirconia electrolyte stabilized in this way, the first
If you follow the process shown in the figure to create a raw sheet by crushing and slurrying and using a thermoplastic resin as an organic binder using the Lid-Tree-V method, the cell electrode part and the current collector part will be screen-printed. 0 that can be easily formed
A raw sheet made of the same material is inserted as a spacer for forming a hollow cylinder between two raw sheets printed in this way, and after being heat-pressed and integrally formed, the inner and outer surfaces of the hollow cylinder are sintered. An oxygen gas concentration battery consisting of a group of single cells having electrodes is obtained. However, when connecting a desired number of individual cells in series or parallel, each cell - y are close to each other on the same plane], or y = y with a large potential difference after connection is the substrate. There are many cases where it is necessary to separate and cross electrolytes. In such a case, it is necessary to lift the lea r part from the base electrolyte surface or to insert an insulating layer between it and the base electrolyte. For high-temperature insulating ceramics, aluminum alloys are usually used, but in manufacturing methods such as the raw sheet method, where it is desirable to complete all the arrangements before firing (as much as possible), different element oxides are used. Yr
If used, the problem is that it reacts with the substrate during firing, and the difference in mutual diffusion rate is minute, making it easy to generate racks, resulting in a lack of reliability. This was done by paying attention to the phenomenon that the electrical conductivity decreases when a stabilizer such as Y-08 is dissolved in zirconia in an amount greater than the amount that gives the maximum electrical conductivity. By using materials that are exactly the same but differ only in composition ratio, the high-resistance layer (hereinafter referred to as the insulating layer) and the substrate zirconia electrolyte layer can be sintered without forming crystallographically different layers. To provide a method for preventing leakage of an oxygen gas concentration battery, which can be completely integrated at times, and can obtain an insulating layer with high electrical insulation properties that can withstand use even when formed in a heat-compressed part that requires airtightness. It is an object.

The invention will be explained using a simplified model experiment example. Figure 2 shows the composition of the test piece used to fully verify the electrical insulation effect and the integrity of the bond.First, zirconia powder stabilized with Y*0 mol%
Raw sheets 1 and 1at containing I divinyl 1 teral as an organic pine filler and l lyethylene glycol and octyl 7 talate as dusting agents were prepared. Next, as a paint for forming an insulating layer, 18 mol% or more and 60 mol%
The following Y*0st-added zirconia (ZrO*) powder is mixed with dia-7ton alcohol, cellosolve, ethylene chloride,
The above paint is dispersed in a mixed solution of Rusolz acetate and xylene, and the above paint is applied by screen printing to both sides of the green sheet L, facing each other, and this is dried at 80°C to form electrically insulating layers 2 and 21. Tube formed. Next, after forming the entire platinum pane on this, the raw sheet 1a is platinum-r3a
Place the platinum wire 4 on top of each other so as to embed a part of it between 1a and 1a, and press it into a press equipped with a heating plate.15
Heat and pressure bonding was carried out at 0°C. This sample was subjected to debinding treatment for +/- minutes at a temperature of 300°C to 500°C, and then heated to 160°C.
After sintering for 5 hours, a substrate as shown in Figure 3 was obtained. Shirokaneri
Further, a platinum wire is coated with all-platinum paint as a lead wire for I'3, and after baking, the platinum lead 3, 3
The current flowing during the period was measured. The dimensions of the sample are: sheet thickness 9.4 m, insulating layer printing width 5 m, length 301 m)
, thickness 10μ, white margin - p width 4mm, length 30μ, thickness 1
It is 5μ. Figure 4 shows the results of current measurement.

As is clear from Fig. 4, by forming a zirconia layer with a large amount of YOs added to the platinum lea and the zirconia substrate, it is possible to significantly reduce the leakage current. These samples were cooled from 800 °C at a rate of 200 °C per minute, and then
20 cycles of rapid heating and rapid cooling of heating up to 800C at the same rate] After that, the cross sections of each sample were observed at 4 locations using a scanning electron microscope to examine the occurrence of microcracks. In the case of mol%, no abnormality was observed except for the observation of microcracks.

In the above examples, the case where Y*Os' is used as a stabilizer is described.
s.

Rare earth element oxide stabilizers such as Gd and Os may also be used. The reason why the lower limit was set at 18 mol% or more is that the value is clearly expected to be effective when applied industrially.
In addition, the upper limit was set to 50 mol% or less because it was within the range where reliability due to S'-marshock could be ensured. As explained above, according to the method of the present invention, airtightness,
It is possible to form a stable leak prevention layer between the current collectors V without impairing thermal shock characteristics, and it is possible to provide an oxygen gas concentration battery made of a zirconia solid electrolyte with low output power loss.

[Brief explanation of the drawing]

Fig. 1 is a manufacturing flow chart of an oxygen gas concentration battery using a raw zirconia solid electrolyte sheet, Fig. 2 is a perspective view of a test piece showing an embodiment of the present invention before crimping, and Fig. 3 is a view of the test piece after sintering. FIG. 4 is a perspective view of a test piece, and is a leakage current--03 content relationship diagram for explaining the effects of the invention. 1.1a...zirconia raw sheet, 2.2a...screen printed zirconia high resistance layer, 3.3a...platinum current collector')-'s"i...externally taken out platinum thin wire. The same reference numerals in the middle indicate the same or equivalent parts 0 Agent Makoto Kuzuno - Figure 1 Figure 2 Figure 4 Y2O3 is also 1 and % Procedural amendment (spontaneous) Mr. Commissioner of the Japan Patent Office 1, Indication of case Patent application Sho No. 56-119806 No. 2, Title of the invention Oxygen gas neutralization battery C1 - Method for preventing cooling 3, Person making the amendment 5, Subject of the amendment ゛Detailed explanation of the invention in the specification, Contents of amendment No. 9, Line 9 of the amendment r Cart Jk r CaOJ.

Claims (3)

[Claims] (1) In a monooxygen gas concentration battery made of a zirconia solid electrolyte, in order to prevent leakage between the current collector Y and the base electrolyte V, a high resistance layer such as CaO or expanded YsOs is added between the base electrolyte and V. A method for preventing leakage in an oxygen gas concentration battery characterized by forming a stabilized zirconia layer containing 18 mol 5 or more and 50 mol % or less of a rare earth element oxide to increase the electrical insulation between the above 17 + p. ■ (2) A leak prevention method for an oxygen gas concentration battery according to claim 1, wherein the high resistance layer is formed by screen printing. (3) A high-resistance layer is formed in advance by screen printing at necessary locations on a raw zirconia solid electrolyte sheet, after which electrodes and lead tubes are printed, a hollow cylinder is formed by heat and pressure bonding, and then sintered. A method for preventing leakage in an oxygen gas concentration battery according to item 1.