JP3000146B1 - ABC-type hydrogen storage alloy and method for producing the same - Google Patents

Abstract

An inexpensive and lightweight hydrogen storage alloy having excellent hydrogen storage properties is provided. [MEANS FOR SOLVING PROBLEMS] ABC phase (where A element is at least one of alkaline earth elements and rare earth elements, B element is II
At least one kind of group Ib element and C element show at least one kind of group IVb element. An ABC-type hydrogen storage alloy containing (1) as a main component. 2. A _x B _y C _z (where, A element at least one alkaline earth element and rare earth elements, B elements
At least one group IIIb element and C element represent at least one group IVb element. x, y and z are positive numbers;
In addition, the maximum value among them is not more than twice the minimum value. A method for producing an ABC-type hydrogen storage alloy, comprising: forming an alloy raw material having the composition shown in (1) and sintering the formed body at 670 to 880 ° C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ABC-type hydrogen storage alloy and a method for producing the same.

[0002]

2. Description of the Related Art As a hydrogen storage metal capable of storing hydrogen in the form of a compound with a metal (that is, metal hydride), for example, titanium, vanadium, zirconium and the like are known in addition to alkali metals, alkaline earth metals and rare earth elements. ing. As the hydrogen storage alloy, for example, LaNi ₅
AB ₅ type rare earth alloys having a hexagonal CaCu ₅ type crystal structure as represented by, and AB ₂ type having a hexagonal MgZn ₂ type crystal structure or a cubic MgCu ₂ type crystal structure as represented by TiMn _1.5 Laves phase alloy, AB type titanium alloy having a cubic CsCl type crystal structure typified by TiFe, hexagonal Mg ₂ N typified by Mg ₂ Ni
A ₂ B-type magnesium-based alloys having an i-type crystal structure are known.

[0003] These metals and alloys can be hydrogenated (occlusion reaction) or conversely dehydrogenated (dissociation reaction or release reaction) by placing them under a suitable hydrogen pressure and temperature. Metal hydrides can store large amounts of hydrogen in a relatively low hydrogen pressure range, and their storage density per unit volume is comparable to liquid hydrogen. Among them, by directly reacting with hydrogen and a metal or an alloy, it has a property of rapidly absorbing a large amount of hydrogen while rapidly releasing the stored hydrogen, and can reversibly store and release hydrogen. This is called a hydrogen storage alloy.

[0004] Research on utilization technology of hydrogen storage alloys is as follows.
Actively conducted in the field of energy technology.
In fact, hydrogen storage alloys are being put to practical use for applications such as storage and transport of hydrogen, energy conversion media, and negative electrode materials for secondary batteries.

In general, when a hydrogen storage alloy is put into practical use, the following properties are required for the alloy. (1) The hydrogen storage pressure and the hydrogen release pressure should be easy to handle under operating temperature conditions. (2) The plateau should have a constant pressure. Fast (4) A large amount of effective hydrogen that can be repeatedly stored and released under operating temperature conditions and easy-to-handle pressure conditions (5) Easy activation during initial hydrogenation (6) Hydrogen storage and hydrogen Hydrogen pressure difference required for release (hysteresis) is small. (7) Durability against repeated storage and release over a long period. (8) Raw material cost is low. (9) Alloy itself is light. Although hydrogen storage alloys are practically used, they do not necessarily satisfy all of the above conditions (1) to (9), and require the minimum necessary conditions according to the application. They just use what they have.

From this viewpoint, there is a demand for the development of a hydrogen storage alloy satisfying the above conditions (1) to (9), that is, a low-cost and lightweight hydrogen storage alloy having excellent hydrogen storage characteristics.

[0007]

As an inexpensive and lightweight alloy, a calcium-based alloy material is known. Examples of the hydrogen storage alloy belonging to the calcium series include Ca—Ni series alloys represented by CaNi ₅ , and CaMg ₂ , CaA
l _2, and the like.

[0008] However, except for CaNi ₅ , although hydrogen storage / release reactions are observed, 1) high reaction temperature, 2) low reaction activity with hydrogen, 3) low effective hydrogen storage capacity, 4) hydrogen 5) Decomposition occurs due to disproportionation, 5) There is a problem that the dense oxide layer formed on the alloy surface by contact with the atmosphere hinders the hydrogenation reaction, etc. That is nearly impossible. In addition, Ca
Ni ₅ also has a multi-stage dissociation pressure plateau,
There are also problems such as difficulty in manufacturing alloys, and there are still points to be improved in practical use.

On the other hand, the above CaAl ₂ is an intermetallic compound that can be expected as a lightweight and inexpensive hydrogen storage material. However, its hydrogen storage amount is only about 0.5% by weight at room temperature (upper figure in FIG. 1), and its initial activation is also somewhat difficult. There is still room for improvement.

Accordingly, an object of the present invention is to provide an inexpensive and lightweight hydrogen storage alloy having excellent hydrogen storage properties.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the problems of the prior art, and as a result, have found that an alloy having a specific composition can achieve the above object, and finally completed the present invention. Reached.

That is, the present invention relates to the following ABC-type hydrogen storage alloy and a method for producing the same.

1. ABC phase (however, A element is at least one of alkaline earth element and rare earth element, B element is III
At least one element of group b and C element represent at least one element of group IVb. ) As the main constituent , and
ABC phase has hexagonal aluminum boride type crystal structure
And the aluminum site is element A and the boron site is element B
ABC type hydrogen storage alloy occupied by element and C element .

2. A _x B _y C _z (where, A element at least one alkaline earth element and rare earth elements, B elements II
At least one kind of group Ib element and C element show at least one kind of group IVb element. x, y and z are positive numbers, and the maximum value among them is not more than twice the minimum value. ) Is formed into an alloy raw material having the composition shown in
Characterized by sintering at seventy to eight hundred eighty ° C., hexagonal Akiraho
A method for producing an ABC-type hydrogen storage alloy having an aluminum iodide-type crystal structure .

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The hydrogen storage alloy according to the present invention comprises ABC
Phase (however, element A is at least one of alkaline earth elements and rare earth elements, and element B is at least one of group IIIb elements)
The species, element C, represents at least one of the IVb group elements. ) Is the main constituent.

As the alkaline earth element, one or more of beryllium, magnesium, calcium, strontium, barium and the like can be used. Examples of the rare earth element include scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and mixtures Mm thereof. The element A preferably contains at least calcium.

Examples of the group IIIb element include boron, aluminum, gallium, indium and thallium, and one or more of these can be used. The B element preferably contains at least aluminum.

As the above-mentioned IVb group elements, carbon, silicon,
Germanium, tin and lead can be used, and one or more of these can be used. This C element preferably contains at least silicon.

The ABC phase in the present invention preferably contains at least Ca as an A element, at least Al as a B element, and at least Si as a C element (that is, the ABC phase is a CaAlSi-based alloy phase). Is preferred). By forming this CaAlSi-based alloy phase, excellent hydrogen storage properties can be obtained. As the CaAlSi-based alloy phase, for example, CaA
An lSi phase or the like is particularly preferred.

The ABC phase in the present invention generally has a hexagonal aluminum boride (AlB ₂ ) type crystal structure. In this case, it is preferable that the aluminum sites AlB ₂ type crystal structure is the element A, boron site AlB ₂ type crystal structure is occupied by the element B and the element C. ABC
Even when the phase is a CaAlSi-based alloy phase, it is preferable to have the above crystal structure. That is, it is preferable that at least a part of the aluminum site is occupied by Ca and at least a part of the boron site is occupied by Al and Si. For example, when the CaAlSi-based alloy phase is a CaAlSi phase, it is preferable that the aluminum site is occupied by Ca and the boron site is occupied by Al and Si.

[0021] In the hydrogen absorbing alloy of the present invention, the composition of the entire alloy is not particularly limited as long as it has the ABC phase, in particular A _x B _y C _z (where, A element is an alkaline earth elements and rare earth elements At least one of the above, the B element is
At least one group IIIb element and C element represent at least one group IVb element. x, y and z are positive numbers;
In addition, the maximum value is twice or less (preferably 1.5 times or less) the minimum value. ) Is desirable. By taking such an overall composition, more ABC phase can be reliably precipitated. The x, y, and z are positive numbers and may be different from each other as long as the maximum value among them is not more than twice the minimum value, or two or three of these values. May have the same value (the same applies to x, y, and z below).

In the present invention, CaAlSi is used as the ABC phase.
Since system alloy phase is preferred, particularly the composition of the entire alloy _{(Ca 1-a P a)} x (Al 1-b Q b) y (Si 1-c R c) z or (CaP _{a) x} (AlQ _b ) _Y (SiR _c ) _z (where P is at least one of an alkaline earth element and a rare earth element)
Species, Q element is at least one of IIIb group elements, R element is I
Shows at least one Vb group element. 0 ≦ a ≦ 0.2
(Preferably 0 ≦ a ≦ 0.1), 0 ≦ b ≦ 0.2 (preferably 0 ≦ b ≦ 0.1), 0 ≦ c ≦ 0.2 (preferably 0 ≦ c ≦ 0.1), x, y, and z are positive numbers, and the maximum value thereof is twice or less, preferably 1.5 times or less the minimum value. ) Is desirable. By employing this overall alloy composition, more CaA
An lSi-based alloy phase can be reliably formed.

The method for producing the hydrogen storage alloy of the present invention is not particularly limited as long as the above-mentioned ABC phase can be formed.
For example, it can be manufactured by using an alloy raw material having the above-described overall alloy composition and melting or sintering (particularly, solid phase reaction sintering) at a high temperature.

In the present invention, a method based on solid phase reaction sintering is particularly preferred. That is, molding the A _x B _y alloy materials having a composition represented by C _z, usually 670-8 the molded body
A method of sintering at about 80 ° C. is preferable. According to this manufacturing method, a hydrogen storage alloy having an intended alloy composition can be obtained with good reproducibility. In this case, it is preferable to first maintain at the melting point of the component having the lowest melting point or at a temperature slightly higher than that, and then gradually raise the temperature to the final sintering temperature for sintering.

When a CaAlSi-based alloy phase is formed as the ABC phase, the (Ca _1-a P _a ) _x (Al
_1-b Q _b ) _y (Si _{1 -c} R _c ) _z or (CaP _a ) _x (Al
Q _{b) y} (shaping the SiR _c) alloy raw material having a composition represented by _z, it is preferable to sinter the molded body usually about six hundred seventy to eight hundred eighty ° C.. Also in this case, it is preferable to first maintain the melting point of the component having the lowest melting point or at a temperature slightly higher than that, and then gradually raise the temperature to the final sintering temperature for sintering.

The alloy raw material may be obtained by weighing the individual metals, alloys, and the like of each component so as to have the above-mentioned predetermined alloy composition, mixing them according to a known method, and further pulverizing them as necessary. The powder having a particle size of less than 75 μm may be obtained by pulverization. As the alloy raw material in the present invention, for example, empty cans can be used as an Al supply source, and defective or discarded semiconductor products can be used as a Si supply source, as long as a desired alloy composition can be obtained.

In the present invention, it is preferable to use an alkaline earth element-IIIb group element alloy as a part of the alloy raw material. As such an alloy, for example, CaAl _1.8 or the like can be used.

Next, the alloy material is formed into a desired shape. The molding method may be in accordance with a known method, and for example, pressure molding, CIP molding or the like can be employed.
The molding pressure is not particularly limited, but is usually 20 to 30MPa.
It may be about a. Further, in the present invention, the sintering can be performed simultaneously with the sintering by the HIP molding.

The sintering temperature is usually 670 to 88 as described above.
The temperature may be set to 0 ° C., but the sintering time may be appropriately determined according to the sintering temperature or the like. The sintering atmosphere may be an inert gas (helium, argon, etc.) atmosphere. Further, as the sintering device, a known device such as an atmosphere furnace can be used.

The obtained sintered body can be appropriately subjected to known treatments such as annealing and re-melting, if necessary. These processing conditions may be performed according to known conditions.

The ABC type hydrogen storage alloy of the present invention is useful in various applications such as a material for storing hydrogen and a material for transporting hydrogen. These methods of use may be used according to known methods.

[0032]

According to the production method of the present invention, a solid phase reaction sintering method in which the raw material powder is formed (press-formed) prior to sintering and then the formed body is sintered can be employed. Therefore, for example, when Al is used as an alloy raw material, it can also be expected to play a role as a forming aid or a sintering aid because of its excellent spreadability and low melting point (mp = about 660 ° C.). .

Also, components having a high vapor pressure (high vapor pressure components), such as alkaline earth elements, are likely to volatilize at high temperatures, so that under normal production conditions, the alloy weighing stage (planned composition) and the alloy completion stage (Actual composition) in many cases. However, when Al is used as one of the components, the high-vapor-pressure component is substantially covered with Al by melting before the other components. Loss can be suppressed or prevented, and the high vapor pressure component reacts with Al, so that the desired alloy composition can be reliably obtained.

Further, in the solid phase reaction sintering, since the solid phase diffusion phenomenon occurring between metal particles is utilized, it is not necessary to raise the ambient temperature to the melting point of each component of the alloy, and energy saving can be achieved.

[0035]

The ABC type hydrogen storage alloy of the present invention can exhibit excellent hydrogen storage characteristics (hydrogen storage / release speed, etc.) within a wide temperature range, and thus is suitable for hydrogen storage, hydrogen transport, etc. Can be used.

Further, as an alloy raw material, for example, an empty can as an Al supply source and a defective or waste semiconductor product can be used as a Si supply source, so that the product price can be reduced and resource recycling and environmental protection can be achieved. can do.

Further, in the ABC-type hydrogen storage alloy of the present invention, when a light metal such as Al is mainly used, the weight of the alloy itself can be reduced.

[0038]

The present invention will be described below in more detail with reference to examples. The evaluation and analysis of the characteristics and physical properties in the examples were performed by the following methods.

(1) Analysis by powder X-ray diffraction measurement (XRD) The analysis was performed by the Guinier-Heg camera method. A sample for measurement was obtained by kneading the sample alloy powder with Si fine powder for internal standard and liquid paraffin for preventing surface deterioration. This confirmed that the alloy of the present invention had a hexagonal AlB ₂ type crystal structure.

(2) Observation by Scanning Electron Microscope (SEM) A mirror-polished sample alloy using an oil-based abrasive containing fine diamond particles was thoroughly washed and dried, and then subjected to SEM.
Observations were made. Thereby, the alloy structure was observed and the distribution of the constituent components was confirmed.

(3) Wavelength dispersive X-ray spectroscopy (WDX)
A sample for SEM observation was diverted and supplied to WDX.
By this analysis method, the ratio of the constituent components of each part of the alloy structure was measured.

(4) Measurement of Hydrogen Pressure-Composition-Temperature (PCT) Characteristics Prior to the measurement, about 500 mg (particle size: less than 75 μm) of the sample alloy was sealed in a stainless steel measurement reaction vessel.
Initial activation processing was performed. After that, 200 ℃ or less ・ 4M
The PCT characteristics were measured in a hydrogen atmosphere of Pa or less. This measurement confirmed the hydrogen storage capacity and the equilibrium hydrogen dissociation pressure of the alloy.

REFERENCE EXAMPLE 1 A CaAl _1.8 Si _0.2 alloy was prepared by substituting a part of Al which is one of the constituent components in CaAl ₂ with Si.

First, an Al chip and a Si chip were weighed so that Al: Si = 1.8: 0.2 in a molar ratio, and arc melting was performed in a high-purity Ar atmosphere to form a button-shaped Al chip.
_{A 1.8} Si _0.2 alloy was obtained. This alloy was cut into several mm pieces, and Ca particles were further added so as to have the above-mentioned predetermined composition ratio. Then, high-frequency induction melting was performed in a high-purity Ar atmosphere to finally obtain a CaAl _1.8 Si _0.2 alloy. .

The obtained alloy was subjected to powder X-ray diffraction measurement and microstructure observation with a scanning electron microscope. The result is shown in FIG. FIG. 2 shows that the CaAl _1.8 Si
_It can be seen that the _0.2 alloy is composed of two phases, a main phase having a cubic MgCu ₂ type crystal structure and a grain boundary phase having a hexagonal crystal structure.

Next, the hydrogen storage characteristics of the two-phase alloy were evaluated through measurement of PCT characteristics. As a result, as shown in FIG. 1 (lower figure), changes in the equilibrium hydrogen dissociation pressure and operating temperature were hardly observed, but the hydrogen storage amount reached 1.35% by weight at 160 ° C. This hydrogen storage amount is equivalent to about 2.7 times the hydrogen storage amount of the stoichiometric composition alloy CaAl ₂ , and is comparable to the AB ₅ type rare earth alloy which is a typical hydrogen storage alloy currently used. This is the hydrogen storage capacity.

Further, when the alloy structure of the two-phase alloy was examined in detail, the main phase was a Laves phase alloy CaAl _2-δ Si _δ (δ << 1) having a MgCu ₂ type crystal structure. The boundary phase was a novel compound CaAlSi having an AlB ₂ type crystal structure. FIG. 3 shows a schematic diagram of this crystal structure. This crystal structure was determined by comparing and examining the results of composition analysis by wavelength dispersive X-ray spectroscopy, the results of powder X-ray diffraction measurement, and the results of structural analysis by Rietveld analysis based on the intensity data. .

Example 1 A CaAl _1.8 Si alloy containing a relatively large amount of CaAlSi phase was prepared.

First, the CaAl _1.8 S obtained in Reference Example 1 was used.
The _i0.2 alloy was ground in an agate mortar until the particle size was less than 75 μm. Si fine powder (particle size: less than 75 μm) was added to the pulverized product so as to have the above-mentioned predetermined composition, and mixed sufficiently. This mixed powder is filled in a mold and 2
Pressurized at 5MPa to make a tablet-shaped molded body (size φ9mm
× 3 mm). This molded body was sintered at 700 ° C. for 96 hours in a high-purity Ar atmosphere of 0.1 MPa to obtain a sintered body (sintered body alloy).

The structure of the obtained sintered body was examined by powder X-ray diffraction measurement. FIG. 4 shows the results. From the results of FIG. 4, it can be seen that the substance having the hexagonal AlB ₂ type crystal structure and the hexagonal L
a ₂ O ₃ type crystal structure (a hexagonal C
aAl ₂ Ge ₂ type crystal structure. ) Was found to be composed of two phases. In this regard, Ca-Al-Si alloy ternary equilibrium diagram (400 ° C)
Is shown in FIG. Database on intermetallic compound crystals (Edited by P. Villars and LDCalvert, "Pearson's H
andbook of Crystallographic Data for Intermetallic
Phases ", ASM International, vol.1 (1991) p.697), the latter substance is CaAl ₂ S
It was found to be i _2. Further, as a result of performing the Rietveld analysis calculation on the diffraction peak reflecting the AlB ₂ type crystal structure based on the diffraction intensity data obtained here, the calculation result obtained with the crystal parameters described below and the experimental result are shown. He responded very well. From this,
It was confirmed that the substance having an AlB ₂ type crystal structure in this sintered body was CaAlSi. Accordingly, it can be seen that this sintered body is composed of two phases, the CaAlSi phase and the CaAl ₂ Si ₂ phase.

The intermetallic compound of the present invention, CaAlSi having a hexagonal AlB ₂ type crystal structure, is a novel compound for which no crystallographic data has been reported in the past and which has not been published in the equilibrium diagram. Table 1 shows the results of crystal structure analysis of this compound.

[0052]

[Table 1]

Having a hexagonal AlB ₂ type crystal structure, and
ThNi ₂ and ZrBe ₂ have been reported in the past as examples of hydrogen storage alloys capable of reversibly storing and releasing hydrogen. However, it is clear that they belong to the type AB _{2 in} compositional composition, which is essentially different from the ABC type according to the present invention.

Example 2 A hydrogenation treatment was carried out by leaving the sintered body obtained in Example 1 at 200 ° C. for 24 hours in a 3 MPa hydrogen atmosphere in a reaction vessel. Next, the sample taken out of the reaction vessel was pulverized, and its crystal structure was analyzed through powder X-ray diffraction measurement. FIG. 6 shows a powder X-ray diffraction pattern. Crystallinity is
It deteriorated as a whole with hydrogen-induced amorphization.
Further, since the peak due to the CaAlSi phase is relatively weak, it is understood that the ABC phase contributes to the hydrogen-induced amorphization.

It is considered that the change in the phase and the crystal structure in the sintered body caused by the hydrogenation is due to the hydrogenation of the CaAlSi phase. As a result of calculation assuming that all changes in crystal volume before and after hydrogenation were due to the presence of hydrogen in the crystal, it was estimated that slightly more than 2% by weight of hydrogen was absorbed.
This indicates that the hydride phase CaAlSiH _{2 ± δ} was generated.

FIG. 7 shows CaAl _1.8 containing CaAlSi phase.
3 shows a PCT characteristic curve of a Si alloy (marked by ○). Although this alloy is in a two-phase coexistence state of a CaAlSi phase and a CaAl ₂ Si ₂ phase, the latter hardly exhibits hydrogen storage characteristics in this measurement temperature range.
This can be determined to be due to the presence of the lSi phase. In addition, the measurement results here substantially correspond to the above estimation results.

Example 3 In the CaAl _1.8 Si of Example 1, 5 mol% of Ca
Sintered alloy Ca _0.95 in which the amount corresponding to
La _0.05 Al _1.8 Si was produced in the same manner as in Example 1. When the crystal structure was examined in the same manner as in Example 1, the existence of a hexagonal aluminum boride (AlB ₂ ) type crystal structure was confirmed. Also, in the same manner as in the second embodiment, the PC
The T characteristic was measured. FIG. 8 shows the result.

Examples 4 to 7 Ca _0.91 Sr _0.09 AlSi (Example 4), Ca _0.90 Mg
_0.10 AlSi (Example 5), CaAl _1.5 Ge (CaA
lGe, mixed state of CaAl ₂ Ge ₂ and unknown phase) (Example 6), CaAl _1.5 Si _0.95 Ge _0.05 (CaAlG
e, CaAlSi, CaAl ₂ Ge ₂ and CaAl ₂ Si ₂
Example 1) An alloy having a composition of Example 7
The structure was examined in the same manner as in Example 1. As a result, the existence of a hexagonal aluminum boride (AlB ₂ ) crystal structure was confirmed in each case. The PCT characteristics of each sintered alloy were examined in the same manner as in Example 2. Table 2 shows the maximum hydrogen storage capacity of each sintered alloy.

[0059]

[Table 2]

From the results shown in Table 2, it can be seen that the ABC-type hydrogen storage alloy of the present invention has excellent hydrogen storage properties because the hydrogen storage amount is about 1.2% by weight.

[Brief description of the drawings]

FIG. 1 is a PCT characteristic curve of a CaAl ₂ alloy and a CaAl _1.8 Si _0.2 alloy.

FIG. 2 is a powder X-ray diffraction diagram of CaAl _1.8 Si _0.2 alloy (S
FIG. 6 is a diagram showing the correspondence between the diffraction peak of i and that of an alloy structure (image) due to the Si powder added immediately before measurement for the internal standard.

FIG. 3 is a schematic view of a crystal structure of CaAlSi.

FIG. 4 is a powder X-ray diffraction diagram of a CaAl _1.8 Si sintered body.

FIG. 5 is a ternary phase diagram of a Ca—Al—Si alloy (Edited by
P. Villars, A. Prince and H. Okamoto, "Handbook of Te
rnary Alloy Phase Diagrams (Second Printing) ", ASMI
excerpt from nternational (1997)).

FIG. 6 is a powder X-ray diffraction diagram of a CaAl _1.8 Si sintered alloy after standing in a hydrogen atmosphere.

FIG. 7 shows a PCT characteristic curve of a CaAl _1.8 Si sintered body.

FIG. 8 shows a PCT characteristic curve of a Ca _0.95 La _0.05 AlSi sintered body.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuo Sakai 1-38-31 Midorioka, Ikeda-shi, Osaka Prefecture Inside the Osaka Institute of Technology (72) Inventor Sei Uehara 1- 8-31 Midorioka, Ikeda-shi, Osaka No. Osaka Institute of Industrial Technology, Institute of Industrial Science (72) Inventor Doug Noreus S-10691, Stockholm, Sweden, Sweden (56) References JP-A-10-8180 (JP, A) JP-A-8-13076 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 21/00-21/18 B22F 3/10 C22C 1/04

Claims (8)

(57) [Claims] An ABC phase (where A represents at least one element of an alkaline earth element and a rare earth element, B represents at least one element of a group IIIb element, and C element represents at least one element of a group IVb element). As a main component , and AB
The C phase has a hexagonal aluminum boride type crystal structure,
Luminium site is element A, boron site is element B and
ABC type hydrogen storage alloy occupied by C element . 2. A composition of the entire alloy A _x B _y C _z (where, A element at least one alkaline earth element and rare earth elements
Species, element B is at least one element of group IIIb, and element C is I
Shows at least one Vb group element. x, y and z are positive numbers, and the maximum value among them is not more than twice the minimum value. ABC-type hydrogen storage alloy of claim 1, wherein represented by). 3. The ABC phase contains at least Ca as an A element, at least Al as a B element,
2. The ABC according to claim 1, which contains at least Si as an element.
Type hydrogen storage alloy. 4. The ABC phase has a hexagonal aluminum boride type crystal structure, wherein at least a part of aluminum sites is occupied by Ca, and at least a part of boron sites is Al
The ABC-type hydrogen storage alloy according to claim 3 , occupied by Si and Si. It is 5. The overall alloy composition _{(Ca 1-a P a)} x (Al
_1-b Q _b ) _y (Si _{1 -c} R _c ) _z or (CaP _a ) _x (Al
Q _b ) _y (SiR _c ) _z (provided that P is at least one of alkaline earth elements and rare earth elements, Q is at least one of Group IIIb elements, and R is at least one of Group IVb elements) 0 ≦ a ≦ 0.2, 0 ≦ b ≦ 0.2, 0 ≦ c
≦ 0.2, x, y and z are positive numbers, and the maximum value among them is not more than twice the minimum value. The ABC-type hydrogen storage alloy according to claim 3 or 4 , wherein 6. A _x B _y C _z (where, A element at least one alkaline earth element and rare earth elements, B elements IIIb
At least one element of group IV and element C represent at least one element of group IVb. x, y and z are positive numbers, and
The maximum value is less than twice the minimum value. ) Is formed into an alloy raw material having the composition shown in FIG.
Hexagonal boride characterized by sintering at ~ 880 ° C
Method for producing ABC-type hydrogen storage alloy having aluminum type crystal structure. 7. _{(Ca 1-a P a)} x (Al 1-b Q b) y (Si
_1-c R _c ) _z or (CaP _a ) _x (AlQ _b ) _y (SiR _c ) _z
(However, P element is at least one of alkaline earth elements and rare earth elements, and Q element is at least one of IIIb group elements.)
The species and the R element represent at least one of the IVb group elements. 0 ≦
a ≦ 0.2, 0 ≦ b ≦ 0.2, 0 ≦ c ≦ 0.2, x, y
And z are positive numbers, and the maximum value among them is not more than twice the minimum value. ), And sintering the formed body at 670 to 880 ° C., wherein the hexagonal aluminum boride type crystal structure is formed.
A method for producing an ABC-type hydrogen storage alloy having : As 8. Some alloy materials, production method according to claim 6 or 7 using an alkaline earth element -IIIb group element alloy.