JPH10294115A - Solid electrolytic thin film and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine, thermally stable, solid electrolytic thin film of high crystallinity and high oxygen ion conductivity, and its manufacturing method for allowing the solid electrolytic thin film to be produced in a short length of time. SOLUTION: An electrolytic material 8, which is made by adding one or more third ingredients out of aluminum oxide (Al2 O3 ), bismuth oxide (Bi2 O3 ), chromium oxide (Cr2 O3 ) and iron oxide (Fe2 O3 ) to zirconium monoxide (ZrO) containing metallic yttrium (Y), is heated and evaporated by irradiating high density arc discharge plasma flow 13; at the same time the evaporated particles are transformed into plasma. Then, these evaporated particles transformed into plasma are fed on to a porous electrode base plate 12; thereby, a solid, electrolytic thin film made of zirconium oxide (ZrO2 ) containing one or more gradients out of yttrium oxide (Y2 O3 ), aluminum oxide (Al2 O3 ), bismuth oxide (Bi2 O3 ), chromium oxide (Cr2 O3 ) and iron oxide (Fe2 O3 ) are formed on the porous electrode base plate 12 under an oxygen atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a solid electrolyte thin film incorporated in a fuel cell and a method for producing the same.

[0002]

2. Description of the Related Art A fuel cell incorporating a solid electrolyte thin film includes a flat solid electrolyte fuel cell having a flat electrolyte, fuel electrode and air electrode, and a cylindrical fuel cell having a cylindrical electrolyte, fuel electrode and air electrode. There is a solid oxide fuel cell. As shown in FIG. 3, as a flat-plate type solid electrolyte fuel cell, a fuel electrode 101 and an air electrode 102 are attached to both sides of a solid electrolyte 100 to constitute one unit, and a plurality of units are connected in series via a separator 103. Is known.

The solid electrolyte material, fuel electrode material, air electrode material, and separator material include zirconium oxide in which yttrium oxide is dissolved, cermet of nickel and zirconium oxide, lanthanum manganite in which strontium oxide is dissolved, and strontium oxide. Lanthanum chromite in which magnesium oxide is dissolved is used. The materials of the solid electrolyte 100 and the separator 103 are required to be dense.

[0004] The power generation efficiency of a flat plate type solid oxide fuel cell increases as the electrical resistance along the current path of the constituent material, that is, the electrical resistance in the thickness direction decreases. Among the constituent materials, the one having the highest electric resistivity is a solid electrolyte material. Therefore, it is required that the solid electrolyte 100 be made as thin as possible while ensuring mechanical strength and denseness.

[0005] Conventional technologies satisfying these requirements include:
For example, an electrochemical deposition method for producing a solid electrolyte membrane on a porous electrode substrate is known. This method is described in, for example, "Fuel Cell (1984)" by Takehiko Takahashi.

[0006]

SUMMARY OF THE INVENTION Aluminum oxide (Al ₂ O ₃ ), bismuth oxide (Bi ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), oxide By adding iron (Fe ₂ O ₃ ) or the like, it is possible to improve mechanical strength and denseness. However, the electrochemical deposition method has a problem that it is difficult to add these third components.

Further, the electrochemical vapor deposition method requires complicated temperature control using expensive metal chloride as a raw material.
There are also many problems, such as the need for delicate pressure management and the inability to produce a large-area solid electrolyte membrane.

[0008] The present invention has been made in view of such problems of the prior art, and has as its object to provide a dense, highly crystalline, thermally stable, and high oxygen ion conductivity. An object of the present invention is to provide a solid electrolyte thin film and a manufacturing method capable of manufacturing the solid electrolyte thin film in a short time.

[0009]

In order to solve the above-mentioned problems, the solid electrolyte thin film according to the first aspect of the present invention comprises 6 to 12 mol% of yttrium oxide (Y ₂ O ₃ ) and _{2 to 20} mol% of aluminum oxide (Al). ₂ O ₃ ), bismuth oxide (Bi
₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), iron oxide (Fe ₂ O ₃ )
Of zirconium oxide (ZrO ₂ ) containing at least one of the above.

[0010] The method for producing a solid electrolyte thin film according to claim 2 comprises:
A method of forming an electrolyte thin film by irradiating a high-density arc discharge plasma stream to heat and evaporate an electrolyte material, and at the same time, evaporating particles into plasma, and supplying the plasmaized evaporating particles onto a porous electrode substrate, The electrolyte material is aluminum oxide (Al ₂ O ₃ ), bismuth oxide (Bi ₂ O ₃ ), and chromium oxide (ZrO) with respect to a conductive material of zirconium monoxide (ZrO) containing 7 to 11 wt% of metal yttrium (Y). Cr ₂ O ₃ ) and at least one third component of iron oxide (Fe ₂ O ₃ ) in a total amount of 2 to 12 watts.
a material added so as to have a concentration of 6 to 12 mol% of yttrium oxide (Y ₂ O ₃ ) on the porous electrode substrate in an oxygen atmosphere and aluminum oxide ( _{2 to 20} mol%) in an oxygen atmosphere. Al ₂ O ₃ ), bismuth oxide (Bi
₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), iron oxide (Fe ₂ O ₃ )
A solid electrolyte thin film made of zirconium oxide (ZrO ₂ ) containing at least one of the above.

[0011] The method for producing a solid electrolyte thin film according to claim 3 comprises:
3. The method for producing a solid electrolyte thin film according to claim 2, wherein the arc discharge plasma flow is a plasma composed of a mixed gas of Ar gas and O ₂ gas, and has an oxygen partial pressure of 0.35 mT.
orr to 0.85 mTorr.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a schematic configuration diagram of a film forming apparatus for performing the method of the present invention, and FIG. 2 is a scanning electron micrograph showing the particle structure of a solid electrolyte thin film formed on a porous electrode substrate by the method of the present invention. It is.

As shown in FIG. 1, a film forming apparatus includes a vacuum vessel 1, a crucible 2 and a permanent magnet 3 installed inside the vacuum vessel 1, and a plasma generating cathode 4 installed on a side of the vacuum vessel 1. , An intermediate electrode 5 and an air-core coil 6.

The inside of the vacuum vessel 1 is evacuated from an exhaust port 7 by a vacuum exhaust pump (not shown). The crucible 2 also serves as a discharge anode, and is loaded with a material 8 for evaporation. Immediately below the crucible 2, a permanent magnet 3 equipped with a water cooling mechanism
Are arranged, whereby a vertical magnetic field B _V is formed.

The plasma generating cathode 4 installed on the side of the vacuum vessel 1 is composed of a composite cathode of Ta pipe and LaB ₆ , and the plasma generating cathode 4 has a discharge gas inlet 9 for introducing a discharge gas. ing. Also, the intermediate electrode 5
Is for drawing plasma into the vacuum vessel 1,
The air-core coil 6 is for generating a horizontal magnetic field B _H.

The crucible 2 serving as both the plasma generating cathode 4 and the discharge anode is electrically connected by a low-voltage / high-current DC power supply 10, and a DC voltage is applied between the plasma generating cathode 4 and the crucible 2. As a result, a large current plasma flow 13 is generated. The plasma flow 13 drawn into the vacuum vessel 1 by the intermediate electrode 5 is
Bent 90 degrees directly above the crucible 2 by a synthetic magnetic field of the magnetic field B _V in the vertical direction by the horizontal direction magnetic field B _H and crucible 2 permanent magnet 3 immediately below by, is applied to the electrolyte material 8 in the crucible 2.

The oxygen gas introduced into the vacuum vessel 1 during film formation is supplied to a gas inlet 1 provided on the side of the vacuum vessel 1.
Introduced from 1. Further, the porous electrode substrate 12 for forming a thin film is disposed immediately above the crucible 2.

The operation of the film forming apparatus configured as described above will be described. After a discharge gas is introduced into the vacuum vessel 1 through a discharge gas inlet 9, a DC power supply is provided between the plasma generating cathode 4 provided on the side surface of the vacuum vessel 1 and the electrolyte material 8 in the crucible 2 serving also as a discharge anode. 10 applies a DC voltage.

Then, a large-current DC arc discharge plasma flow 13 is generated and irradiated on the electrolyte material 8, so that the electrolyte material 8 is heated, evaporated and turned into plasma. At this time, zirconium monoxide (ZrO) containing metal yttrium (Y)
Can maintain a stable discharge because it has electrical conductivity at room temperature.

Aluminum oxide (Al ₂ O ₃ ), bismuth oxide (Bi ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ) and iron oxide (Fe ₂ O ₃ ) added as the third component are solid electrolytes. It acts to suppress the formation of crystal grain boundaries in the thin film.

Further, an oxygen gas is introduced into the vacuum chamber 1 from the gas inlet 11 and a film is formed in an oxygen atmosphere activated in a high-density plasma to form a crystal on the surface of the porous electrode substrate 12. A dense solid electrolyte thin film having high properties, being thermally stable, and having high oxygen ion conductivity is formed.

Further, since the plasma flow 13 irradiating the electrolyte material 8 is a large current plasma of 150 A or more,
It is possible to increase the evaporation rate of the electrolyte material 8 and to generate high-density plasma because the discharge mode is arc discharge, and to form a dense solid electrolyte thin film on the porous electrode substrate 12 in a short time. Is done.

Since the film forming means in the present invention is a kind of vapor deposition technique for forming a thin film by heating and evaporating a material, the composition of the evaporating material can be easily changed, and zirconium monoxide (ZrO) is used. At least of metal yttrium (Y), aluminum oxide (Al ₂ O ₃ ), bismuth oxide (Bi ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), and iron oxide (Fe ₂ O ₃ ) as the _{second component} The addition of one or more third components can be facilitated.

As a high-density arc discharge plasma flow generator usable in the present invention, for example, “Vacuum No. 25
Vol. 10, No. 10 (published in 1982) ", a discharge cathode combining a composite cathode plasma generator and a pressure gradient plasma generator can be used, but a device capable of generating a large current arc discharge plasma flow. If so, there is no particular limitation.

Example 1 The following procedure was performed using an electrolyte material 8 in which aluminum oxide (Al ₂ O ₃ ) was added as a third component to zirconium monoxide (ZrO) containing metal yttrium (Y) as an evaporation source. According to nickel (N
A solid electrolyte thin film was formed on a porous electrode substrate 12 formed of i) and a cermet of zirconium oxide (ZrO), and the oxygen ion conductivity, denseness, and composition of the formed solid electrolyte thin film were evaluated.

The denseness was evaluated by measuring the amount of nitrogen gas permeated at room temperature. As the composition of the film, a method of simultaneously identifying a film formed on a quartz substrate by ICP analysis (inductively coupled plasma emission spectroscopy) was used.

After the inside of the vacuum vessel 1 is evacuated to a pressure of 5 × 10 ⁻⁶ Torr or less by a vacuum exhaust pump, Ar gas is discharged as a discharge gas through the discharge gas inlet 9 at 30 scc.
m, and a DC power of 200 A is supplied between the plasma generating cathode 4 and the crucible 2 to generate a large-current arc discharge plasma flow. The crucible 2 is charged with a material containing metal yttrium (Y) in a certain ratio with respect to zirconium monoxide (ZrO) as an electrolyte material 8 to be evaporated.

After the plasma flow 13 generated by the plasma generating cathode 4 is introduced into the vacuum vessel 1 by the intermediate electrode 5 and the air-core coil 6, a magnetic field B _V formed by the permanent magnet 3
Irradiates the center of the electrolyte material 8 with the
Was heated and evaporated. At this time, an oxygen gas of about 200 sccm is introduced into the vacuum vessel 1 from the gas inlet 11 to react the oxygen gas with the evaporating particles to form a thin film on the substrate 12 placed directly above the crucible 2 for about 60 minutes. Carried out.

The pressure inside the vacuum vessel 1 before the introduction of the oxygen gas is determined by the evacuation speed and the flow rate of the Ar gas, and the pressure at this time was 2.5 × 10 ⁻⁴ Torr. The pressure after the introduction of the oxygen gas, that is, the pressure during the film formation was 7.5 × 10 ⁻⁴ Torr. The results of forming the solid electrolyte thin film by changing the composition of the electrolyte material 8, that is, the contents of the metal yttrium (Y) and the aluminum oxide (Al ₂ O ₃ ) with respect to zirconium monoxide (ZrO) are summarized in Table 1 below. Was.

[0030]

[Table 1]

As shown in Table 1, the concentration of yttrium oxide (Y ₂ O ₃ ) in the solid electrolyte thin film was 6 to 12 mol%,
The concentration of aluminum oxide (Al ₂ O ₃ ) is ₂ to 20 mol
%, Good oxygen ion conductivity and denseness are obtained.
It has favorable characteristics as a solid electrolyte thin film used for a thin film fuel cell.

On the other hand, when the concentration of yttrium oxide (Y ₂ O ₃ ) is 5 mol% or less or 13 mol% or more,
Due to the phase transformation of the solid electrolyte thin film at the time of heating at about 1000 ° C., as a result of cracks occurring in the thin film and a decrease in gas shielding properties, it is preferable as the solid electrolyte thin film used in the thin film fuel cell used in the present invention. Absent.

When aluminum oxide (Al ₂ O ₃ ), which is the third component in the solid electrolyte thin film, is 2 mol% or less, the effect of suppressing the formation of crystal grain boundaries in the solid electrolyte thin film is insufficient. Since gas shielding performance cannot be obtained sufficiently,
It is also not preferable as a solid electrolyte thin film used for a thin film fuel cell which is an application of the present invention. When aluminum oxide (Al ₂ O ₃ ) is 21 mol% or more, the gas shielding performance is good, but the oxygen ion conductivity is reduced, so that it is used in the thin film fuel cell used in the present invention. Not suitable for solid electrolyte thin films.

FIG. 2 shows 9 wt% metallic yttrium (Y).
5 shows a cross-sectional SEM observation photograph of a solid electrolyte thin film formed on a porous electrode substrate 12 using an electrolyte material 8 containing 5 wt% aluminum oxide (Al ₂ O ₃ ). It can be seen from FIG. 2 that a dense thin film having no crystal grain boundaries is formed over about 20 μm.

Example 2 Zirconium monoxide (Zr)
5% by weight of bismuth oxide (Bi ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), and iron oxide (Fe) as a third component for a material containing 9 wt% of metal yttrium (Y) with respect to O).
_A solid electrolyte thin film was prepared in the same manner as in Example 1 using the material to which ₂ O ₃ ) was added, and was evaluated.

In any case, as in the case of aluminum oxide (Al ₂ O ₃ ) shown in Example 1, a thin film which has good oxygen ion conductivity and gas shielding properties and is used in the present invention. It was determined to be a solid electrolyte thin film suitable for a fuel cell. The results in Example 2 are summarized in Table 2 below.

[0037]

[Table 2]

Example 3 Zirconium monoxide (Zr)
O), a material containing 9 wt% of metal yttrium (Y) and a material obtained by adding 5 wt% of aluminum oxide (Al ₂ O ₃ ) as a third component were used. Oxygen partial pressure of 0.3mTorr and 0.9mT
A solid electrolyte thin film was formed on quartz glass under the conditions of orr.

When the oxygen partial pressure is 0.3 mTorr, strong optical absorption is observed in the thin film. Further, when the crystallinity is evaluated by the X-ray diffraction method, a diffraction pattern of stabilized zirconium (YSZ) is slightly observed. However, it was found that the thin film had low crystallinity.

When the oxygen partial pressure is 0.9 mTorr,
Although a transparent thin film is obtained, the evaporated electrolyte material 8 itself is oxidized due to excessive supply of oxygen to the film formation atmosphere. As a result, the electrical conductivity of the evaporated material is reduced and the instability of discharge is reduced. Occurred. Due to the instability of the discharge, the deposition rate was reduced to about 60% of the case where the oxygen partial pressure was 0.5 mTorr. From these results, the optimum oxygen partial pressure in the present invention is 0.35 mTo
rr to 0.85 mTorr.

[0041]

As described above, according to the solid electrolyte thin film according to the first aspect, zirconium oxide (ZrO ₂ ) in which yttrium oxide (Y ₂ O ₃ ) is dissolved is used as a third component as aluminum oxide (Al). ₂ O ₃ ), bismuth oxide (B
i ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), iron oxide (Fe
By adding ₂ O ₃ ) or the like, mechanical strength is improved and denseness is improved.

Further, according to the method for producing a solid electrolyte thin film according to the second or third aspect, zirconium oxide (ZrO ₂ ) in which yttrium oxide (Y ₂ O ₃ ) is dissolved as aluminum oxide (Al) as a third component. ₂ O ₃ ), bismuth oxide (B
i ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), iron oxide (Fe
By adding ₂ O ₃ ) or the like, a solid electrolyte thin film capable of improving mechanical strength and improving denseness can be produced on a porous electrode substrate.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a film forming apparatus that performs a method of the present invention.

FIG. 2 is a scanning electron micrograph showing the particle structure of a solid electrolyte thin film formed on a porous electrode substrate according to the method of the present invention.

FIG. 3 is a diagram showing a cell structure of a flat solid electrolyte fuel cell;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 2 ... Crucible, 3 ... Permanent magnet, 4 ... Plasma generating cathode, 5 ... Intermediate electrode, 6 ... Air-core coil, 8 ... Electrolyte material, 9 ... Discharge gas inlet, 10 ... DC power supply, 12 ... Porous electrode substrate, 13 ... plasma flow.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichi Hishinuma 6-36-1, Kamariya Higashi, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Etsuo Ogino 3-5-1, Doshumachi, Chuo-ku, Osaka-shi, Osaka Japan Inside Sheet Glass Co., Ltd. (72) Inventor Takayuki Toshima 3-5-1-11 Doshomachi, Chuo-ku, Osaka-shi, Osaka Prefecture Inside Japan Sheet Glass Co., Ltd. (72) Inventor Nakai Hidemi 3-5-1, Doshomachi, Chuo-ku, Osaka, Osaka No. Inside Nippon Sheet Glass Co., Ltd.

Claims (3)

[Claims] 1. Yttrium oxide (Y ₂ O ₃ ) of 6 to 12 mol%, aluminum oxide (Al ₂ O ₃ ), bismuth oxide (Bi ₂ O ₃ ), and chromium oxide (Cr ₂ ) within a range of _{2 to 20} mol%. O ₃ ) and zirconium oxide (ZrO ₂ ) containing at least one of iron oxide (Fe ₂ O ₃ ). 2. An electrolyte material is heated and evaporated by irradiating a high-density arc discharge plasma flow, and at the same time, evaporated particles are turned into plasma. The plasma-formed evaporated particles are supplied onto a porous electrode substrate to form an electrolyte thin film. In the forming method, the electrolyte material is aluminum oxide (Al ₂ O ₃ ) and bismuth oxide (Bi ₂ O ₃ ) with respect to a conductive material of zirconium monoxide (ZrO) containing 7 to 11 wt% of metal yttrium (Y). ), Chromium oxide (Cr ₂ O ₃ ), iron oxide (F
e ₂ O ₃ ) is a material in which at least one or more third components are added so that the total amount thereof is 2 to 12 wt%.
2 mol% yttrium oxide (Y ₂ O ₃ )
Oxidation containing at least one of aluminum oxide (Al ₂ O ₃ ), bismuth oxide (Bi ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), and iron oxide (Fe ₂ O ₃ ) in a mol% range. A method for producing a solid electrolyte thin film, comprising forming a solid electrolyte thin film made of zirconium (ZrO ₂ ). 3. The solid electrolyte thin film according to claim 2, wherein the arc discharge plasma flow is a plasma composed of a mixed gas of Ar gas and O ₂ gas, and has an oxygen partial pressure of 0.35 mTorr to 0.85 mTorr. Production method.