JPH05263254A - Formation of thin film of cati1-xfexo3 - Google Patents

Abstract

PURPOSE:To form the CaTi1-xFexO3 film which is thin and dense. CONSTITUTION:A CVD device is constituted by boring holes 2a, 2b, 2c, 2d in a block 1, connecting one end of cylindrical chambers 3a, 3d, 3c to the apertures of the holes 2a, 2b, 2c, constituting the other ends of the respective cylindrical chambers 3a, 3d, 3c as carrier gas introducing ports, providing heating furnaces 4a, 4b, 4c around these chambers, using the inside of the cylindrical chambers 3a, 3d, 3c as evaporating chambers and disposing boats 5a, 5d, 5c to be mounted with raw materials within these evaporating chambers. The front end of a cylindrical reaction chamber 6 is connected to the small- diameter hole 2d and a substrate 7 is set in this reaction chamber 6. A heating furnace 8 is provided on the outer periphery of the chamber 6 and a mixer is disposed in the upstream position of the substrate 7. A reactive gas supply pipe 10 is inserted from near the front end of the reaction chamber 6 toward the substrate 7 so as to penetrate the part of this mixer.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a chemical vapor deposition method (CV).
D) is used to form a CaTi _1-x Fe _x O ₃ thin film on the surface of the substrate.

[0002]

2. Description of the Related Art Solid electrolytes having conductivity to specific ions within a single crystal phase are used as materials for gas separation membranes, oxygen pumps, fuel cells and the like. Then, a mixed conductor in which the solid electrolyte is further provided with electronic conductivity has recently received attention. The mixed conductor is in the form of a perovskite type oxide, and specifically, LaMnO ₃ is used as a base material and Mn is used.
Of La _1-x MnSr _x O ₃ in which a part of Co is replaced by Sr, and La _1-x CoSr in which a part of Co is replaced by Sr with LaCoO ₃ as a matrix
Examples thereof include CaTi _1-x Fe _x O _{3 in which x} O ₃ and CaTiO ₃ are the base materials and a part of Ti is substituted with Fe.

[0003]

Among the above-mentioned mixed conductors, La _1-x MnSr _x O ₃ and La _1-x CoSr _x O ₃ contain a small amount of oxygen (10 ^-3 to 10) at high temperature (1000 ° C). ^-4 torr)
In the state, it is reduced and becomes non-conductive. Therefore, for example, when a mixed conductor is used as an oxygen gas separation membrane, when oxygen separation proceeds and the oxygen partial pressure decreases, it becomes impossible to perform further gas separation and the like, and the function as a gas separation device is reduced. It will not end. On the other hand, CaTi _1-x
Fe _x O ₃ is not reduced even in a vacuum state of about 10 ⁻⁸ torr at 1000 ° C. and has a gas separation ability, but there is a problem in how to form a dense and thin film.

That is, in the past, as means for forming a thin film made of a perovskite type oxide, Japanese Patent Laid-Open No. 57-
A sintering method as disclosed in Japanese Patent No.
Thermal spraying method or EV as disclosed in JP-A-3-156
D (Electorochemical Vapor Deposition) is known.

However, in the case of the sintering method, the thickness of the mixed conductor formed cannot be made thin. For example, when the mixed conductor is applied to a gas separation device, the power (electric power or suction force) required for gas separation is required. It becomes big. Further, in the case of the thermal spraying method, the mixed conductor formed is porous and inferior in denseness, so that the purity of the gas to be separated is lowered, and in EVD, since a corrosive gas is used, the surface of the mixed conductor is reduced. The substrate formed on the substrate may deteriorate.

[0006]

In order to solve the above-mentioned problems, the present invention separately heat vaporizes a metal compound raw material containing a Ca atom, a metal compound raw material containing a Fe atom and a metal compound raw material containing a Ti atom, Next, these vaporized metal compound raw materials are conveyed to the mixing section by the carrier gas and mixed, and further the mixed metal compound raw materials are conveyed to the reaction section where the substrate is set by the carrier gas, and O _{2 is} supplied to the reaction section.
Of a reaction gas containing carbon is introduced onto the surface of the substrate to produce CaTi _1-x Fe _x O ₃
Was allowed to precipitate.

[0007]

Since an organic metal compound or the like that does not generate a corrosive gas is used, the substrate is not altered and a thin and dense film can be formed.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 shows a CVD for carrying out the method of the present invention.
1 is a schematic configuration diagram of an apparatus, in which a CVD apparatus has holes 2a, 2b, 2c and 2d which are assembled in the block 1 in a block 1, and a cylindrical chamber 3 is provided at openings of the holes 2a, 2b and 2c.
a, 3d, 3c are connected at one end, and each cylindrical chamber 3
The other ends of a, 3d, 3c are used as carrier gas inlets for N ₂ , Ar, He, etc., and heating furnaces 4a, 4 are provided around them.
b, 4c are provided, the insides of the cylindrical chambers 3a, 3d, 3c are vaporized chambers, and the boat 5 for loading the raw materials into these vaporized chambers
a, 5d, and 5c are arranged.

The tip of a cylindrical reaction chamber 6 is connected to the small diameter hole 2d, and a substrate 7 made of alumina, stabilized zirconia or the like is set in the reaction chamber 6,
A heating furnace 8 is provided on the outer periphery of the reaction chamber 6, and a substrate 7
A mixer 9 is arranged at a position further upstream than the reaction gas (O ₂ , H ₂ O, H ₂ + CO) from the vicinity of the tip of the reaction chamber 6 toward the substrate 7 so as to penetrate the portion of the mixer 9.
₂ etc.) supply tube 10 is inserted.

The above apparatus is characterized in that the optimum vaporization temperature can be set for each different raw material and the temperatures of the mixing section and the reaction section can be controlled. Therefore, each heating furnace 4a, 4b, 4c, 8 A thermocouple thermometer 11 is inserted inside and at the confluence of the holes 2a, 2b, 2c, and the position of the substrate 7 is movable so that the length L of the mixing part from the confluence to the substrate 7 can be adjusted.

Alumina substrate 7 is formed by using the above CVD apparatus.
A method of forming a CaTi _1-x Fe _x O ₃ thin film on the surface of the will be described below. First, Ca (C ₁₁ H ₁₉ O ₂ ) ₂ is used as a metal compound raw material containing Ca atoms, and Fe (C ₁₁ H ₁₉ O ₂ ) ₂ or Fe (C ₅ H ₇ O ₂ ) is used as a metal compound raw material containing Fe atoms.
₃ as Ti (C ₁₁ H) as a metal compound raw material containing a Ti atom.
₁₉ O ₂ ) ₄ or Ti (OCH ₃ ) ₄ is prepared, and Ca (C ₁₁ H
₁₉ O ₂ ) ₂ in the boat 5a, Fe (C ₁₁ H ₁₉ O ₂ ) ₂ or Fe (C ₅ H ₇ O ₂ ) ₃ in the boat 5d, Ti (C ₁₁ H 2
₁₉ O ₂ ) ₄ or Ti (OCH ₃ ) ₄ is set on the boat 5c, respectively. Here, the boat 5 in the case of using a raw material _{Ti (O-i-C 3} H 7) 4 as a raw material liquid containing Ti atoms
Instead of c, a pressure vessel 12 as shown by the imaginary line in the figure is used. In the following, Fe (C ₅ H ₇ O ₂ ) is used as the Fe raw material.
₃ and an example using Ti (OCH ₃ ) ₄ as the Ti raw material will be described.

After the raw materials are set in the boats 5a, 5b and 5c as described above, the pressure in the reaction chamber 6 is set to 2
Set to a desired value in the range of 760 torr. Then, the raw materials in the boats 5a, 5b, 5c are heated and vaporized in the heating furnaces 4a, 4b, 4c. The specific heating temperature is Ca
(C ₁₁ H ₁₉ O ₂ ) ₂ is 200 to 500 ° C., and Fe (C ₅ H 2
₇ O ₂ ) ₃ is 150 to 160 ° C., Ti (OCH ₃ ) ₄ is 20 to 160 ° C.
25 ° C., and the temperature in the reaction chamber 6 is 400 to 900 ° C.
Adjusted within the range. The carrier gas is N ₂ (100
Up to 200 cc / min) and the reaction gas is O ₂ (30 to 120 c
c / min), and further, the length L of the mixing portion was adjusted to 5 to 50 cm to deposit crystals of CaTi _1-x Fe _x O _{3 on} the surface of the substrate.
The temperature of the mixing portion is controlled to be higher than the temperature at which the vaporized metal compound recrystallizes and lower than the temperature at which nuclei of the metal oxide are generated.

From the above experiment, the following points were clarified. (1) The temperature in the reaction chamber 6 is set to 500 ° C. or higher, and the length L of the mixing section is set to 20 cm or more, so that CaTi _1-x Fe
_{An xO 3} single phase was obtained. (2) The ratio of Ca to Fe and Ti can be controlled by the vaporization temperature of the raw material. (3) As a result of the gas permeability test, the film produced under the conditions that the pressure in the reaction chamber 6 was 2 to 200 torr, the temperature was 600 ° C. or higher, and the length L of the mixing part was 20 cm or higher was dense. (4) The length L of the mixing section could be reduced to 10 cm by using the mixer.

FIG. 2 shows the Ca produced by the method of the present invention.
FIG. 2 is a cross-sectional view of a gas separation device to which a Ti _1-x Fe _x O ₃ thin film is applied, and this gas separation device has a partition wall 21 made of an oxygen ion electron mixed conductor (CaTi _1-x Fe _x O ₃ ) in a case 20. When one is exposed to air and the other is sucked, a short circuit occurs due to electronic conduction in the partition. Then, oxygen permeates from the high oxygen partial pressure chamber to the other. The CaTi _1-x Fe _x O ₃ thin film produced by the present invention can be used not only for gas separation devices but also for electrodes of fuel cells and the like.

[0015]

As described above, according to the present invention, by selecting Ca _1-x Fe _x TiO ₃ as a mixed conductor, ionic conductivity and electronic conductivity can be obtained even at high temperature and high vacuum (low oxygen concentration). The chemical vapor deposition method is applied as a method of forming the mixed conductor on the surface of the substrate so that thin and dense mixed conductor crystals can be formed on the surface of the substrate. When applied to a gas separation device or a fuel cell, it is possible to manufacture a high-performance product with low running cost.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a CVD apparatus for carrying out the method of the present invention.

FIG. 2 is a schematic configuration diagram of a gas separation device using a mixed conductor obtained by the method of the present invention.

[Explanation of symbols]

1 ... Block, 2a, 2b, 2c, 2d ... Hole, 3a, 3
d, 3c ... Cylindrical chamber, 4a, 4b, 4c, 8 ... Heating furnace, 5a, 5d, 5c ... Boat, 6 ... Reaction chamber, 7 ... Substrate, 9 ... Mixer, 10 ... Reaction gas supply pipe, 2
1 ... Partition wall.

Claims (1)

[Claims] 1. A metal compound raw material containing a Ca atom, a metal compound raw material containing an Fe atom and a metal compound raw material containing a Ti atom are separately heated and vaporized, and then these vaporized metal compound raw materials are mixed with a carrier gas. To the reaction part where the substrate is set by the carrier gas, and the reaction gas containing O ₂ is introduced into this reaction part to introduce CaTi _1-x F
A method for forming a CaTi _1-x Fe _x O ₃ thin film, characterized in that crystals of e _x O ₃ are deposited.