JP3414699B2 - Oxide ceramic cold storage material and its manufacturing method - Google Patents
Oxide ceramic cold storage material and its manufacturing methodInfo
- Publication number
- JP3414699B2 JP3414699B2 JP2000175128A JP2000175128A JP3414699B2 JP 3414699 B2 JP3414699 B2 JP 3414699B2 JP 2000175128 A JP2000175128 A JP 2000175128A JP 2000175128 A JP2000175128 A JP 2000175128A JP 3414699 B2 JP3414699 B2 JP 3414699B2
- Authority
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- Japan
- Prior art keywords
- rare earth
- ceramics
- beads
- regenerator
- oxide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Compositions Of Oxide Ceramics (AREA)
Description
【０００１】[0001]
【発明の利用分野】本発明は、酸化物セラミックス蓄冷
材に関するもので、特に４.２Ｋ以下等の極低温環境で
用いるのに適した、新規な酸化物セラミックス蓄冷材と
その製造方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide ceramics regenerator material, and more particularly to a novel oxide ceramics regenerator material suitable for use in an extremely low temperature environment of 4.2K or less and a method for producing the same. is there.
【０００２】[0002]
【従来技術】従来から、超電導マグネットやＭＲＩ冷却
用の冷凍機として、液体ヘリウム温度（４.２Ｋ）が発
生可能な小型気体冷凍機が多用されている。この小型冷
凍機では、ヘリウム冷媒と共に、蓄冷材としてＲXＭ
（Ｒ：Ｄｙ，Ｈｏ，Ｅｒ等の希土類元素，Ｍ：Ｎｉ，Ａ
ｌ等の金属元素）に代表される希土類金属間化合物が用
いられている。2. Description of the Related Art Conventionally, small gas refrigerators capable of generating liquid helium temperature (4.2K) have been widely used as refrigerators for cooling superconducting magnets and MRI. In this small refrigerator, together with helium refrigerant, R X M
(R: rare earth element such as Dy, Ho, Er, M: Ni, A
A rare earth intermetallic compound typified by a metal element such as 1) is used.
【０００３】冷凍機の冷凍能力や最低到達温度は、冷凍
機の蓄冷器に用いる蓄冷材の比熱に依存し、蓄冷材はヘ
リウム冷媒以上の比熱を有する物質であることが必要で
ある。上記の希土類金属間化合物は、２０〜５Ｋ付近の
温度領域で大きな比熱を有しており、極低温用冷凍機に
は欠かせないものとなっている。The refrigerating capacity and the minimum attainable temperature of the refrigerator depend on the specific heat of the regenerator material used in the regenerator of the refrigerator, and the regenerator material is required to be a substance having a specific heat higher than that of helium refrigerant. The above-mentioned rare earth intermetallic compound has a large specific heat in the temperature range of about 20 to 5K and is essential for a cryogenic refrigerator.
【０００４】一方、近年の超伝導技術の実用化や高感度
センサーの開発に向け、４.２Ｋ以下の温度領域まで冷
却できる冷凍機が必要とされ始めている。しかしながら
この温度領域では、上記の希土類金属間化合物の比熱は
激減し、冷凍効率が低下し、最低到達温度も３Ｋ程度に
止まってしまう。On the other hand, for practical use of superconducting technology and development of high-sensitivity sensor in recent years, a refrigerator capable of cooling to a temperature range of 4.2 K or less is required. However, in this temperature range, the specific heat of the rare earth intermetallic compound is drastically reduced, the refrigerating efficiency is lowered, and the minimum attainable temperature is stopped at about 3K.
【０００５】蓄冷器に充填される蓄冷材は、ヘリウム冷
媒との熱交換を効率よく行うため、直径が０.０５〜０.
８mm程度のビーズ形状で用いられている。ビーズ形状と
されるのは、ヘリウム冷媒が蓄冷器を通過する際の圧力
損失を低減するためと、冷凍機の機械的振動等による蓄
冷材の破砕や摩耗を防止して、冷凍機のシールの損傷な
どによる冷凍機の性能低下を防止するためである。４.
２Ｋ以下の温度で大きな比熱を有する物質として、Ｇｄ
ＡｌＯ3単結晶が知られており、ＧｄＡｌＯ3単結晶をビ
ーズ状に加工して蓄冷材とすることも考えられるが、単
結晶は高価であり、小さなビーズ形状へ加工することも
困難である。The regenerator material filled in the regenerator has a diameter of 0.05 to 0.5 in order to efficiently exchange heat with the helium refrigerant.
It is used in a bead shape of about 8 mm. The bead shape is to reduce the pressure loss when the helium refrigerant passes through the regenerator, and to prevent the regenerator material from being crushed or worn due to mechanical vibration of the refrigerator, thereby preventing the refrigerator from sealing. This is to prevent performance deterioration of the refrigerator due to damage or the like. 4.
As a substance having a large specific heat at a temperature of 2 K or less, Gd
An AlO 3 single crystal is known, and it may be considered that the GdAlO 3 single crystal is processed into beads to be used as a cold storage material, but the single crystal is expensive and it is difficult to process it into a small bead shape.
【０００６】[0006]
【発明の課題】本発明は、４.２Ｋ以下の極低温環境で
高い比熱を有し、かつサーマルショックへの耐久性を有
し、かつ冷凍機運転中の破砕や摩耗が少ない、新規な酸
化物セラミックス蓄冷材と、その製造方法とを提供する
ことを目的とする。DISCLOSURE OF THE INVENTION The present invention provides a novel oxidation which has a high specific heat in a cryogenic environment of 4.2K or less, has a durability against a thermal shock, and has little crushing and wear during operation of a refrigerator. An object of the present invention is to provide a ceramics cold storage material and a manufacturing method thereof.
【０００７】[0007]
【発明の構成】本発明の酸化物セラミックス蓄冷材は、
組成がＲXＡｌ2-XＯ3（Ｒは１種以上の原子番号５７〜
７１の希土類元素を表し、０.３≦Ｘ＜１で、Ｘ＝１を
除く）の多結晶焼結体ビーズからなるものである。好ま
しくは、Ｘを０.８≦Ｘ≦０.９９５とし、より好ましく
は０.９８≦Ｘ≦０.９９０とする。また多結晶焼結体ビ
ーズは、ペロブスカイト相のＲＡｌＯ3組織内に、アル
ミナもしくは希土類−アルミニウムガーネット組織が分
散したものであることが好ましい。The oxide ceramic regenerator material of the present invention comprises:
The composition is R X Al 2-X O 3 (R is at least one atomic number 57 to
71 represents a rare earth element, and 0.3 ≦ X <1, and X = 1
(Excluding ) the polycrystalline sintered body beads. Preferably, X is 0.8 ≦ X ≦ 0.995, and more preferably 0.98 ≦ X ≦ 0.990. Further, it is preferable that the polycrystalline sintered body beads have alumina or a rare earth-aluminum garnet structure dispersed in the RAlO 3 structure of the perovskite phase.
【０００８】この発明の酸化物セラミックス蓄冷材の製
造方法は、ＢＥＴ比表面積が１〜１５m2/gで、実質的に
遊離の希土類単酸化物を含有せず、かつ組成がＲXＡｌ
2-XＯ3（Ｒは１種以上の原子番号５７〜７１の希土類元
素を表し、０.３≦Ｘ＜１で、Ｘ＝１を除く）の、原料
粉末をビーズ状に成形して焼結するようにしたものであ
る。好ましくは、焼結温度を１６００〜１８００℃とす
る。The method for producing an oxide ceramics regenerator material of the present invention has a BET specific surface area of 1 to 15 m 2 / g, contains substantially no free rare earth monoxide, and has a composition of R X Al.
A raw material powder of 2-X O 3 (R represents one or more kinds of rare earth elements with atomic numbers 57 to 71, and 0.3 ≦ X <1 and X = 1 is excluded ) is formed into beads and baked. It was made to tie. Preferably, the sintering temperature is 1600 to 1800 ° C.
【０００９】[0009]
【発明の作用と効果】本発明者等は前記の課題を解決す
べく種々検討を行った。その結果、一般式ＲXＡｌ2-XＯ
3（Ｒは１種以上の希土類元素を表し、Ｘは０.３≦Ｘ＜
１で、Ｘ＝１を除く数である）で表される多結晶焼結体
ビーズが、極低温で大きな比熱を有していると共に、蓄
冷材として用いるのに十分な強度を有していることを見
出した。The function and effect of the present invention The present inventors have made various studies in order to solve the above problems. As a result, the general formula R X Al 2-X O
3 (R represents one or more rare earth elements, X is 0.3 ≦ X <
The polycrystal sintered body beads represented by 1 and a number other than X = 1 ) have a large specific heat at an extremely low temperature and have sufficient strength to be used as a regenerator material. I found that.
【００１０】ただし、市販の希土類酸化物とアルミニウ
ム酸化物とを、単に混合してビーズ状に成形、焼結して
も、十分な強度を有するセラミックスは得られなかっ
た。セラミックス原料粉末に関して、詳細に検討した結
果、緻密で、高強度のセラミックスを得るには、原料粉
末の組成並びに化学種と、その比表面積が大きな影響を
及ぼしていることを見出した。However, even if a commercially available rare earth oxide and an aluminum oxide were simply mixed and shaped into beads and sintered, a ceramic having sufficient strength could not be obtained. As a result of detailed examination of the ceramic raw material powder, it was found that the composition and chemical species of the raw material powder and its specific surface area have a great influence on obtaining dense and high-strength ceramics.
【００１１】原料粉末の組成は一般にＲXＡｌ2-XＯ
3（Ｒは原子番号５７〜７１の希土類元素で、以下同
様）で表され、ここでＸの値を０.３≦Ｘ＜１とする必
要があり、Ｘが１を越えると、実使用時のビーズの破壊
確率が急増し、またサーマルショックへの耐久性も低下
した。Ｘの値はビーズの強度と比熱の双方に影響し、Ｘ
が１から減少すると４Ｋ付近での比熱が減少し、ビーズ
の強度はＸ＝１からＸ＝０．９９０の間で急増し、０．
９８未満では再度強度が減少して、０．８ないし０．７
以下ではさらに強度が低下する。そこでＸに関して、
０.８≦Ｘ≦０.９９５が好ましく、より好ましくは０.
９８≦Ｘ≦０.９９０とする。なおＸの値が０.３以下で
は、焼結後のセラミックスの化学種の大半が比熱の小さ
いアルミナ相となる。The composition of the raw material powder is generally R X Al 2-X O
3 (R is a rare earth element with atomic number 57 to 71, the same applies below), and it is necessary to set the value of X to 0.3 ≦ X <1. The probability that the beads will break rapidly increased, and the durability against thermal shock also decreased. The value of X affects both the strength and specific heat of the beads,
As the specific heat decreases from 1 to 4, the specific heat near 4K decreases, and the bead strength sharply increases between X = 1 and X = 0.990,
If it is less than 98, the strength is reduced again to 0.8 to 0.7.
Below, the strength is further reduced. So with respect to X,
0.8 ≦ X ≦ 0.995 is preferable, and more preferably 0.9
98 ≦ X ≦ 0.990. When the value of X is 0.3 or less, most of the chemical species of the ceramics after sintering become the alumina phase having a small specific heat.
【００１２】希土類酸化物とアルミナとの反応により生
成する化学種には、Ｒ3Ａｌ5Ｏ12のガーネット構造、Ｒ
ＡｌＯ3のペロブスカイト構造、Ｒ4Ａｌ2Ｏ9のモノクリ
ニック構造がある。ところで原料粉末組成がこれらの組
成範囲にあっても、粉末Ｘ線回折法による測定で、原料
粉末中に希土類酸化物が単独で存在する場合、緻密で機
械的強度の高いセラミックスを得ることは困難であっ
た。これは、希土類酸化物が単独で存在すると、焼結過
程で、希土類酸化物とアルミナとの反応生成物が種々変
化し、その都度化合物の密度が変化するため、セラミッ
クスの組織にマイクロクラックが生じるためと、一応考
えることができる。The chemical species produced by the reaction between the rare earth oxide and alumina include R 3 Al 5 O 12 garnet structure, R
There are a perovskite structure of AlO 3 and a monoclinic structure of R 4 Al 2 O 9 . By the way, even if the raw material powder composition is in these composition ranges, it is difficult to obtain a dense and high mechanical strength ceramics when a rare earth oxide is present alone in the raw material powder as measured by a powder X-ray diffraction method. Met. This is because when the rare earth oxide is present alone, the reaction products of the rare earth oxide and alumina change variously in the sintering process, and the density of the compound changes each time, so that microcracks occur in the structure of the ceramics. I can think for a while.
【００１３】緻密なセラミックス蓄冷材を得るには、原
料粉末の比表面積も重要な影響を及ぼす。なおこの明細
書では、比表面積はＢＥＴ法で測定した比表面積を意味
し、ＢＥＴ比表面積を単にＢＥＴと簡略に記載すること
がある。蓄冷材として一般に用いられている直径０.０
５mm〜０.８mm程度のビーズを成形する手法としては、
押し出し法で紐状の成形体を得て、必要寸法にカットし
た後丸める方法や、ビーズの製造方法として昔から広く
用いられている、ドラム造粒法、転動造粒法、液中造粒
法等が上げられる。いずれの手法により成形しても、比
表面積が１m2/g以下では原料粉末自体が焼結性に乏し
く、緻密なセラミックスは得られない。また１５m2/g以
上では押し出し法の場合、押出圧力が異常に高くなるた
め成形できず、また他の成形方法では原料粉末の凝集性
が強いために、目的とする成形体の径よりも小さな単位
で団粒となり易く、結果的にいびつな形状の成形体しか
得られず、また成形体には団粒と団粒との隙間に大きな
気孔が生成し易くなる。従って、原料粉末の比表面積は
１〜１５m2/gとし、好ましくは３〜１０m2/gとし、より
好ましくは４〜７m2/gとする。In order to obtain a dense ceramics cold storage material, the specific surface area of the raw material powder also has an important influence. In this specification, the specific surface area means the specific surface area measured by the BET method, and the BET specific surface area may be simply described as BET. The diameter generally used as a cold storage material is 0.0
As a method for molding beads of about 5 mm to 0.8 mm,
Drum granulation method, tumbling granulation method, submerged granulation method, which has been widely used for a long time as a method of obtaining a string-shaped compact by extrusion, cutting it to the required size and then rounding it, and a method of manufacturing beads. Laws, etc. are raised. Regardless of which method is used, if the specific surface area is 1 m 2 / g or less, the raw material powder itself has poor sinterability, and dense ceramics cannot be obtained. Also, if the extrusion method is more than 15 m 2 / g, the extrusion pressure will be abnormally high and molding will not be possible. In other molding methods, the cohesiveness of the raw material powder will be strong, so the diameter will be smaller than the diameter of the target Aggregates tend to be formed as a unit, and as a result, only a distorted shaped compact is obtained, and large pores are easily generated in the gap between the aggregates in the compact. Therefore, the specific surface area of the raw material powder is 1 to 15 m 2 / g, preferably 3 to 10 m 2 / g, and more preferably 4 to 7 m 2 / g.
【００１４】酸化物セラミックス蓄冷材の製造では、原
料粉末を製造するため、ボールミル等の混合粉砕機を用
いて市販の希土類酸化物とアルミナとを目的組成に混合
し、次いで８００℃〜１３００℃程度に加熱して仮焼
し、希土類・アルミニウム化合物とする。用いる希土類
酸化物やアルミナの、粒径や活性度の違いにより、反応
温度や生成する化学種は変化するが、混合粉末の仮焼後
に、粉末Ｘ線回折測定により希土類酸化物が単独で存在
しなくなる条件を求めて用いる。なお均一性の観点から
は、湿式合成により原料粉末を調整するのが好ましく、
特開平１０−１０１３３３号公報記載の重炭酸アンモニ
ウムを沈殿剤として用いる方法や、特開平２−９２８１
７号公報記載の尿素法等が好適に用いられる。In the production of the oxide ceramics regenerator material, in order to produce a raw material powder, a commercially available rare earth oxide and alumina are mixed with a target composition using a mixing pulverizer such as a ball mill, and then about 800 ° C to 1300 ° C. It is heated and calcined to obtain a rare earth / aluminum compound. Although the reaction temperature and the chemical species to be generated change depending on the particle size and activity of the rare earth oxide or alumina used, the rare earth oxide alone is present by powder X-ray diffraction measurement after calcination of the mixed powder. It is used in search of the condition that disappears. From the viewpoint of uniformity, it is preferable to prepare the raw material powder by wet synthesis,
A method using ammonium bicarbonate as a precipitating agent described in JP-A-10-101333, and JP-A-2-9281.
The urea method and the like described in Japanese Patent No. 7 are preferably used.
【００１５】得られた希土類・アルミニウム化合物が反
応時の熱処理により焼き固まっている場合には、乳鉢や
ボールミルにより軽く粉砕する。ただし、特別に小さく
する必要はなく、特に比表面積から予想される粒子径以
下にまで小さくしてはならない。この理由は、上記した
ように団粒が生じ易くなり、緻密な成形体の作製に困難
が生じるためである。If the obtained rare earth / aluminum compound is baked and solidified by the heat treatment during the reaction, it is lightly crushed by a mortar or a ball mill. However, it is not necessary to make it particularly small, and in particular, it should not be made smaller than the particle size expected from the specific surface area. The reason for this is that, as described above, aggregates are likely to be generated, which makes it difficult to produce a dense molded body.
【００１６】このようにして得られた原料粉末を、既知
の成形方法によりビーズ形状に成形する。押し出し法を
用いた場合には、後の焼成工程において脱脂工程を設け
る必要があることから、ドラム造粒や転動造粒そして液
中造粒法等のほとんどバインダーを必要としない成形法
を用いるのが好ましい。The raw material powder thus obtained is molded into a bead shape by a known molding method. When the extrusion method is used, it is necessary to provide a degreasing step in the subsequent firing step. Therefore, a molding method that requires almost no binder, such as drum granulation, tumbling granulation or submerged granulation, is used. Is preferred.
【００１７】このようにして得られた成形体を例えば脱
脂後に焼結する。焼結雰囲気は真空中や水素中などいず
れでも良く、特に限定されないが、大気中で充分であ
る。焼成温度は用いる原料粉末の活性度や成形体の密度
によるが、およそ１６００℃〜１８００℃で２〜３時間
焼結すれば、緻密なセラミックスが得られる。The molded body thus obtained is sintered, for example, after degreasing. The sintering atmosphere may be either in vacuum or in hydrogen, and is not particularly limited, but it is sufficient in the air. The firing temperature depends on the activity of the raw material powder used and the density of the compact, but dense ceramics can be obtained by sintering at about 1600 ° C to 1800 ° C for 2 to 3 hours.
【００１８】[0018]
【実施例】以下、本発明の実施例を説明するが、本発明
はこれらに限定されるものではない。EXAMPLES Examples of the present invention will be described below, but the present invention is not limited thereto.
【００１９】[0019]
【実施例１】市販の酸化ガドリニウム（ＢＥＴ：５m2/
g）の７２.５ｇと酸化アルミニウム（ＢＥＴ：３m2/g）
の２０.４ｇとをボールミルに入れ、エタノールを媒液
として２４時間混合した。得られたスラリーを、ビーカ
ーに移し取り、下部より加熱してエタノールを蒸発させ
て乾燥混合粉末とした後、アルミナ坩堝に入れて１３０
０℃で３時間加熱（仮焼）した。得られた粉末のＸ線回
折測定を行ったところ、ＧｄＡｌＯ3の単一相であっ
た。また比表面積（ＢＥＴ）値は４.３m2/gであった。Example 1 Commercially available gadolinium oxide (BET: 5 m 2 /
g) of 72.5 g and aluminum oxide (BET: 3 m 2 / g)
Was placed in a ball mill and mixed with ethanol as a medium for 24 hours. The obtained slurry was transferred to a beaker, heated from the bottom to evaporate ethanol to obtain a dry mixed powder, which was then placed in an alumina crucible and put in a 130
It was heated (calcined) at 0 ° C. for 3 hours. When X-ray diffraction measurement was performed on the obtained powder, it was a single phase of GdAlO 3 . The specific surface area (BET) value was 4.3 m 2 / g.
【００２０】この粉末を乳鉢で軽く粉砕した後、金型を
用いて４０mmΦ×３mmのディスク状とし、１９６ＭＰａ
の圧力でコールドアイソスタティックプレス（ＣＩＰ）
成形した。次いで、この成形体を通常の大気炉を用いて
１６５０℃の温度で３時間焼結した。なお昇温及び降温
は５００℃／時間とした。This powder was lightly crushed in a mortar and then made into a disc shape of 40 mmΦ × 3 mm by using a mold, and 196 MPa.
Cold isostatic press (CIP) with pressure
Molded. Next, this compact was sintered at a temperature of 1650 ° C. for 3 hours using a normal atmospheric furnace. The temperature rise and fall was set to 500 ° C./hour.
【００２１】得られた焼結体の比熱を図１に示す。また
図１には、酸化ガドリニウムの代わりに６４.６ｇの酸
化ジスプロシウム（ＢＥＴ：６.２m2/g）を用いて得た
ＤｙＡｌＯ3の比熱と、従来から低温用蓄冷材に用いら
れているＨｏＣｕ2の比熱も示した。図１から、ＧｄＡ
ｌＯ3やＤｙＡｌＯ3セラミックスが、従来のＨｏＣｕ2
に比べて、極低温で大きな比熱を持っていることが分か
る。The specific heat of the obtained sintered body is shown in FIG. Further, FIG. 1 shows the specific heat of DyAlO 3 obtained by using 64.6 g of dysprosium oxide (BET: 6.2 m 2 / g) instead of gadolinium oxide, and HoCu which has been conventionally used as a cold storage material for low temperature. A specific heat of 2 is also shown. From Figure 1, GdA
lO 3 and DyAlO 3 ceramics, traditional HoCu 2
It can be seen that it has a large specific heat at extremely low temperature, compared to.
【００２２】[0022]
【実施例２】酸化ガドリニウムの量を変えて蓄冷材セラ
ミックスでの組成因子Ｘを変化させた以外は、実施例１
と同様にして蓄冷材セラミックスを作製し、比熱を測定
した。図２に、４Ｋ付近に現れる比熱のピークの値を示
す。図２から、ＧｄXＡｌ2-XＯ3においてＸの値が０.３
≦Ｘ≦１.５の範囲で従来の金属間化合物よりも大きな
比熱を持つことが分かり、Ｘが１以下でＸの値を減少さ
せると比熱も単調に減少することが分かる。なおＸの値
が１以下で、Ｘを減少させると比熱が減少するのは他の
希土類元素でも同様で、その原因は比熱の小さなアルミ
ナ組織が多量に含まれるようになるためであった。Ｘの
値を変えた試料について、Ｘ線回折で組織の種類を求
め、ビーズの断面について、電子顕微鏡で組織の分布状
況を調べた。Ｘ＝１の場合、ペロブスカイト組織のみが
認められ、Ｘ＜１の場合、ＧｄXＡｌ2-XＯ3ではペロブ
スカイト組織中にアルミナが均一に分散し、同様にして
調整した他の試料では、希土類元素がＥｕやＮｄ，Ｃｅ
の場合も同様にペロブスカイト組織中にアルミナが均一
に分散し、Ｄｙ，Ｅｒ，Ｔｍ，Ｙｂ，Ｌｕの場合は、ペ
ロブスカイト組織中にガーネット組織が均一に分散して
いた。[Example 2] Example 1 except that the composition factor X in the regenerator ceramics was changed by changing the amount of gadolinium oxide.
The regenerator material ceramics were produced in the same manner as in 1. and the specific heat was measured. FIG. 2 shows the peak value of the specific heat that appears near 4K. From FIG. 2, the value of X is 0.3 in Gd X Al 2-X O 3 .
It can be seen that the specific heat is larger than that of the conventional intermetallic compound in the range of ≤X≤1.5, and that when X is 1 or less and the value of X is decreased, the specific heat is also monotonically decreased. Note that when the value of X is 1 or less, the specific heat decreases when X is decreased in the same manner as in other rare earth elements, and the reason is that a large amount of alumina structure having a small specific heat is included. The types of tissues were determined by X-ray diffraction for samples with different X values, and the distribution state of the tissues was examined for the cross section of the beads with an electron microscope. When X = 1, only the perovskite structure was observed, and when X <1, Gd X Al 2 -X O 3 had alumina dispersed uniformly in the perovskite structure, and other samples prepared in the same manner showed rare earth elements. Elements are Eu, Nd, Ce
Similarly, in the case of, alumina was uniformly dispersed in the perovskite structure, and in the case of Dy, Er, Tm, Yb, and Lu, the garnet structure was uniformly dispersed in the perovskite structure.
【００２３】[0023]
【実施例３】０.５mol/Ｌの硝酸ホルミウム水溶液３０
Ｌと、０.５mol/Ｌの硝酸アルミニウム水溶液３０Ｌを
混合して混合水溶液とした。アンモニア水を加えてpH
８.０とした２mol/Ｌの炭酸水素アンモニウム水溶液６
０Ｌ中に、この混合水溶液を２.８Ｌ/分の速度で滴下し
た。この際、硝酸ホルミウムと硝酸アルミニウムの混合
水溶液並びに重炭酸アンモニウム水溶液は、共に恒温槽
中において２５℃に維持した。滴下終了後、２５℃で２
４時間熟成した後、濾過、水洗を４回繰り返し、１４０
℃で４８時間乾燥した。[Example 3] 0.5 mol / L holmium nitrate aqueous solution 30
L and 30 L of a 0.5 mol / L aluminum nitrate aqueous solution were mixed to prepare a mixed aqueous solution. PH by adding aqueous ammonia
2 mol / L ammonium hydrogen carbonate aqueous solution of 8.0 6
This mixed aqueous solution was added dropwise to 0 L at a rate of 2.8 L / min. At this time, both the mixed aqueous solution of holmium nitrate and aluminum nitrate and the aqueous ammonium bicarbonate solution were maintained at 25 ° C. in a constant temperature bath. After finishing the dropping, 2 at 25 ℃
After aging for 4 hours, filtration and washing with water are repeated 4 times.
Dry at 48 ° C for 48 hours.
【００２４】このアモルファス沈殿を８００℃〜１６０
０℃の種々の温度で３時間仮焼し、比表面積の異なるＨ
ｏＡｌＯ3の原料粉末を得た。次いで実施例１と同様に
して成形し、１７００℃で３時間焼結した。仮焼温度の
変化に伴う、原料粉末の比表面積の変化と、焼結後のセ
ラミックスの密度の変化とを表１に示す。表１より、比
表面積が１m2/g以下では緻密なセラミックスは得られな
いことが分かる。This amorphous precipitate is treated at 800 ° C. to 160 ° C.
Calcination is performed for 3 hours at various temperatures of 0 ℃, and H with different specific surface areas
A raw material powder of oAlO 3 was obtained. Then, it was molded in the same manner as in Example 1 and sintered at 1700 ° C. for 3 hours. Table 1 shows the change in the specific surface area of the raw material powder and the change in the density of the ceramics after the sintering due to the change in the calcination temperature. It can be seen from Table 1 that dense ceramics cannot be obtained when the specific surface area is 1 m 2 / g or less.
【００２５】得られた原料粉末を用いて、結合剤として
水のみを用いた転動造粒法により直径約１mmのビーズ形
状に成形した後、１７００℃で３時間焼結した。得られ
たセラミックスを破砕し、内部の微構造を観察した。そ
の結果、比表面積が１５m2/gを超えるものでは１μm程
度の気孔に加えて１０μmを超える気孔が多数認められ
た。The obtained raw material powder was molded into a bead shape having a diameter of about 1 mm by a tumbling granulation method using only water as a binder, and then sintered at 1700 ° C. for 3 hours. The obtained ceramics were crushed and the internal microstructure was observed. As a result, in the case where the specific surface area exceeds 15 m 2 / g, in addition to the pores of about 1 μm, many pores exceeding 10 μm were recognized.
【００２６】次にセラミックスの強度を比較するため、
１００個のビーズを一辺が約５cmで他辺が約１０cmのビ
ニール袋に入れ、１２０回／分の振蕩機で５分間振った
後に、破砕したビーズの数を調べた。結果を表１に合わ
せて示す。破壊確率は原料粉末の比表面積に依存してお
り、このことから原料粉末の比表面積は１〜１５m2/gが
好ましく、３〜１０m2/gがより好ましく、４〜７m2/gが
最も好ましいことが分かる。Next, in order to compare the strength of ceramics,
100 beads were put in a plastic bag having one side of about 5 cm and the other side of about 10 cm, shaken for 5 minutes on a shaker at 120 times / min, and then the number of crushed beads was examined. The results are also shown in Table 1. Failure probability is dependent on the specific surface area of the raw material powder, the specific surface area is preferably 1~15m 2 / g of the raw material powder Therefore, more preferably 3~10m 2 / g, 4~7m 2 / g and most It turns out to be preferable.
【００２７】[0027]
【表１】 実施例３ （原料粉末の比表面積と蓄冷材セラミックスの焼結密度や破壊確率） 仮焼温度／℃ 比表面積／(m2/g) 焼結密度／％ 破壊確率／％ ８００ １６ ９６ ９１ １０００ １４ ９８ ９ １１００ １０.２ １００ ３ １２００ ７.３ １００ ０ １３００ ４.１ １００ ０ １４００ ３ １００ ２ １５００ １.２ ９７ ９ １６００ ０.８ ９０ １００[Table 1] Example 3 (specific surface area of raw material powder and sintering density and fracture probability of regenerator ceramics) calcination temperature / ° C specific surface area / (m 2 / g) sintering density /% fracture probability /% 800 16 96 91 1000 14 14 98 9 1100 10.2 100 3 1200 7.3 100 0 1300 4.1 4.1 100 0 1400 3 100 2 1500 1500 1.2 97 9 1600 0.8 90 90 100
【００２８】[0028]
【実施例４】実施例３と同様にして、湿式合成法によ
り、種々の組成で一般式がＥｕXＡｌ2 -XＯ3で表される
原料粉末を作製した。仮焼温度は１１００℃とした。こ
れらの原料粉末から、トルエンを媒液とする液中造粒法
により、直径約０.５mmのビーズを作製し、１６５０℃
及び１８００℃で空気中で３時間焼結した。Example 4 In the same manner as in Example 3, raw material powders having various compositions and represented by the general formula of Eu X Al 2 -X O 3 were prepared by a wet synthesis method. The calcination temperature was 1100 ° C. Beads with a diameter of about 0.5 mm were produced from these raw material powders by a submerged granulation method using toluene as a medium, and the beads were produced at 1650 ° C.
And sintered at 1800 ° C. in air for 3 hours.
【００２９】得られたセラミックスの強度を比較するた
め、実施例３と同様にして、振蕩機による破砕試験を実
施した。結果を表２に示す。この結果より、一般式Ｅｕ
XＡｌ2-XＯ3において、Ｘの値が１を超えると極端にセ
ラミックスの強度が低下し、セラミックスの強度はＸの
値に依存することが判明した。なおセラミックスの強度
のＸの値への依存性は、希土類元素をＧｄやＤｙ等の他
の希土類元素に変更した場合でも、希土類元素をＥｕと
した場合と同様であった。実施例２では、Ｘの値が小さ
いと比熱が減少するとの結果が得られており、これらの
点から、酸化物セラミックス蓄冷材の組成では、０.３
≦Ｘ≦１とし、０.８≦Ｘ≦０.９９５が好ましく、０.
９８≦Ｘ≦０.９９が最も好ましいことが判明した。In order to compare the strength of the obtained ceramics, a crushing test by a shaker was carried out in the same manner as in Example 3. The results are shown in Table 2. From this result, the general formula Eu
In X Al 2 -X O 3 , it was found that when the value of X exceeds 1, the strength of ceramics is extremely lowered, and the strength of ceramics depends on the value of X. The dependency of the strength of the ceramics on the value of X was the same as when the rare earth element was changed to Eu even when the rare earth element was changed to another rare earth element such as Gd or Dy. In Example 2, the result that the specific heat is reduced when the value of X is small is obtained, and from these points, the composition of the oxide ceramics regenerator material is 0.3.
≦ X ≦ 1, 0.8 ≦ X ≦ 0.995 is preferred, and
It has been found that 98 ≦ X ≦ 0.99 is most preferable.
【００３０】[0030]
【表２】 実施例４ （Ｘの値と破壊確率） Ｘ １６５０℃破壊確率／％ １８００℃破壊確率／％ ０.２ ０ ２０ ０.３ ０ ２１ ０.４ ０ １６ ０.５ ０ １５ ０.６ ０ １８ ０.７ ０ ９ ０.８ ０ ９ ０.９ ０ ６ ０.９５ ０ ５ ０.９８ ０ ３ ０.９９ ０ ３ ０.９９５ １ ５ １ ３ １０ １.１ ２５ ９８ １.２ ４０ １００ １.３ ９５ １００ １.４ ８５ １００ １.５ ８０ １００ １.６ ７５ １００ １.７ ７８ １００Table 2 Example 4 (value of X and destruction probability) X 1650 ° C. destruction probability /% 1800 ° C. destruction probability /% 0.2 0 20 0.3 0.3 21 21 0.4 0 16 16 0.5 0.5 0 15 0. 6 0 18 0.7 0 9 0.8 0.8 9 9 0.9 0 6 6 0.95 0 5 0.98 0 3 0.99 0 3 0.995 1 5 5 1 3 10 1.1 1 25 98 98 1.2 40 100 1.3 95 100 1.4 85 100 1.5 80 100 100 1.6 75 100 1.7 78 100
【００３１】[0031]
【実施例５】実施例の酸化物セラミックス蓄冷材を用い
た場合の冷凍能力を、消費電力３.３ｋＷの蓄冷型パル
スチュープ冷凍機を用いて調べた。従来の蓄冷器は高温
側と低温側の２段で構成されており、高温側には蓄冷材
としてステンレスが、低温側には鉛、Ｅｒ3Ｎｉそして
ＨｏＣｕ2が、２：１：１の体積割合で高温側から順に
充填されている。酸化物セラミックス蓄冷材で従来の蓄
冷器において最も低温側で大きな比熱を有するＨｏＣｕ
2の２５％を置き換えるように、最低温部に充填した。
酸化物セラミックス蓄冷材は実施例４と同様にして調整
し、焼結温度は１６５０℃とした。Ｇｄ0.99Ａｌ1.01Ｏ
3を用いた場合の結果を図３に示した。図３には、各温
度での酸化物蓄冷材を用いた冷凍機の冷凍能力を、従来
の冷凍機の冷凍能力に対する比として示してある。明ら
かに冷凍能力が向上しており、この効果は希土類元素を
Ｇｄ以外のものとしても同様に認められた。[Embodiment 5] The refrigerating capacity in the case of using the oxide ceramics regenerator material of the embodiment was investigated by using a regenerator type pulse tube refrigerator having a power consumption of 3.3 kW. A conventional regenerator is composed of two stages, a high temperature side and a low temperature side. Stainless steel is used as a regenerator material on the high temperature side, and lead, Er 3 Ni and HoCu 2 have a volume ratio of 2: 1: 1 on the low temperature side. They are filled in order from the high temperature side. HoCu which is an oxide ceramic regenerator material and has a large specific heat at the lowest temperature side in the conventional regenerator
The warmest part was filled so as to replace 25% of 2 .
The oxide ceramic regenerator material was prepared in the same manner as in Example 4, and the sintering temperature was 1650 ° C. Gd 0.99 Al 1.01 O
The result when 3 was used is shown in FIG. FIG. 3 shows the refrigerating capacity of the refrigerator using the oxide regenerator material at each temperature as a ratio to the refrigerating capacity of the conventional refrigerator. Clearly, the refrigerating capacity was improved, and this effect was similarly recognized when the rare earth element was other than Gd.
【００３２】[0032]
【比較例１】実施例１において、乾燥混合粉末を仮焼せ
ずに直接転動造粒により直径約１mmのビーズ形状に造粒
し、１６５０℃並びに１８００℃でそれぞれ３時間焼結
した。実施例３と同様に振蕩機による破壊試験を実施し
たところ、セラミックスビーズは焼結温度によらず９７
％が破壊した。Comparative Example 1 In Example 1, the dry mixed powder was granulated into a bead shape having a diameter of about 1 mm by direct rolling granulation without calcination, and was sintered at 1650 ° C. and 1800 ° C. for 3 hours, respectively. When a destructive test was conducted using a shaker in the same manner as in Example 3, the ceramic beads showed 97 regardless of the sintering temperature.
% Destroyed.
【００３３】[0033]
【実施例６】実施例５と同様にして、Ｘの値を種々に変
化させて調整したＧｄXＡｌ2-XＯ3蓄冷材セラミックス
を冷凍機に用い、室温と３Ｋ付近の最冷温度との間を１
０回繰り返し動作させ、サーマルショックによるビーズ
の破壊状況を調べた。結果を表３に示す。単結晶から調
整した試料に比べ実施例ではサーマルショックへの強度
が高く、特にＸが１未満でサーマルショックへの耐久性
が特に高い。EXAMPLE 6 Analogously to Example 5, variously changing the value of X using a Gd X Al 2-X O 3 regenerator material Ceramics adjusted to the refrigerator, and the most cooling temperature around room temperature and 3K Between 1
The operation was repeated 0 times, and the state of bead breakage due to thermal shock was examined. The results are shown in Table 3. In the examples, the strength against thermal shock is higher than that of the sample prepared from a single crystal, and particularly when X is less than 1, the durability against thermal shock is particularly high.
【００３４】[0034]
【表３】
＊ ＸはＧｄXＡｌ2-XＯ3 でのＸ因子を示す；
＊ 単結晶はＧｄＡｌＯ3 単結晶を蓄冷材セラミック
スと同径のビーズに加工して測定．[Table 3] * X is Gd X Al 2-X shows the X factor in O 3; measured by processing the beads * single crystal and the cold accumulating material ceramics GdAlO 3 single crystal same diameter.
【００３５】以上のように実施例では、サーマルショッ
クへの耐久性が高く、破壊や摩耗により冷凍機を損傷す
るおそれが少なく、しかも極低温での比熱が高く冷凍能
力に優れた、酸化物セラミックス蓄冷材が得られる。As described above, in the examples, the oxide ceramics have high durability against thermal shock, are less likely to damage the refrigerator due to breakage or abrasion, and have high specific heat at extremely low temperatures and excellent refrigerating capacity. A cold storage material is obtained.
【図１】 実施例のＧｄＡｌＯ3焼結体と、ＤｙＡｌＯ3
焼結体、及び従来例のＨｏＣｕ2合金の低温比熱を示す
特性図FIG. 1 shows a GdAlO 3 sintered body of an example and DyAlO 3
Characteristic diagram showing low temperature specific heat of sintered body and HoCu 2 alloy of conventional example
【図２】 ＧｄXＡｌ2-XＯ3焼結体での組成因子ｘと、
４Ｋ付近での比熱のピーク値との関係を示す特性図FIG. 2 is a composition factor x in a Gd X Al 2-X O 3 sintered body,
Characteristic diagram showing the relationship with the peak value of specific heat around 4K
【図３】 ＨｏＣｕ合金の２５％を、Ｇｄ0.99Ａｌ1.01
Ｏ3焼結体で置き換えた際の、３.５Ｋ付近での冷凍能力
の比を示す特性図[Fig. 3] 25% of HoCu alloy, Gd 0.99 Al 1.01
Characteristic diagram showing the ratio of refrigerating capacity around 3.5K when replaced with O 3 sintered body
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開2001−262134（ＪＰ，Ａ) 特開2001−317824（ＪＰ，Ａ) 実開 昭61−86420（ＪＰ，Ｕ) (58)調査した分野(Int.Cl.7，ＤＢ名) C04B 35/42 - 35/50 ＣＡ（ＳＴＮ) ＲＥＧＩＳＴＲＹ（ＳＴＮ) ＪＩＣＳＴファイル（ＪＯＩＳ)─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 2001-262134 (JP, A) JP 2001-317824 (JP, A) Actual development Sho 61-86420 (JP, U) (58) Fields investigated ( Int.Cl. 7 , DB name) C04B 35/42-35/50 CA (STN) REGISTRY (STN) JISST file (JOIS)
Claims (5)
原子番号５７〜７１の希土類元素を表し、０.３≦Ｘ＜
１で、Ｘ＝１を除く）の多結晶焼結体ビーズからなる酸
化物セラミックス蓄冷材。1. A composition of R X Al 2-X O 3 (R represents one or more kinds of rare earth elements having atomic numbers of 57 to 71, and 0.3 ≦ X <
1. The regenerator material for oxide ceramics is composed of polycrystalline sintered beads of 1 ) ( excluding X = 1 ).
ことを特徴とする、請求項１の酸化物セラミックス蓄冷
材。2. The oxide ceramic regenerator material according to claim 1, wherein X satisfies 0.8 ≦ X ≦ 0.995.
イト相のＲＡｌＯ3組織内に、アルミナもしくは希土類
−アルミニウムガーネット組織が分散したものであるこ
とを特徴とする、請求項２の酸化物セラミックス蓄冷
材。3. The oxide ceramic regenerator according to claim 2, wherein the polycrystalline sintered bead has a perovskite phase RAlO 3 structure and an alumina or rare earth-aluminum garnet structure dispersed therein. Material.
的に遊離の希土類単酸化物を含有せず、かつ組成がＲX
Ａｌ2-XＯ3（Ｒは１種以上の原子番号５７〜７１の希土
類元素を表し、０.３≦Ｘ＜１で、Ｘ＝１を除く）の、
原料粉末をビーズ状に成形して焼結するようにした、酸
化物セラミックス蓄冷材の製造方法。4. A BET specific surface area of 1 to 15 m 2 / g, substantially no free rare earth monoxide, and a composition of R X.
Al 2 -X O 3 (R represents one or more kinds of rare earth elements having atomic numbers 57 to 71, 0.3 ≦ X <1, and X = 1 is excluded ),
A method for producing a regenerator material for oxide ceramics, which comprises forming raw material powder into beads and sintering the beads.
あることを特徴とする、請求項４の酸化物セラミックス
蓄冷材の製造方法5. The method for producing a regenerator material for oxide ceramics according to claim 4, wherein the sintering temperature is 1600 to 1800 ° C.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2001262134A (en) * | 2000-03-21 | 2001-09-26 | National Institute For Materials Science | Oxide cold storage material and cold storage device |
| JP5010071B2 (en) * | 2000-07-18 | 2012-08-29 | 株式会社東芝 | Cold storage material, manufacturing method thereof, and refrigerator using the cold storage material |
| JP4256664B2 (en) * | 2002-11-12 | 2009-04-22 | 神島化学工業株式会社 | Method for producing rare earth vanadium oxide ceramics |
| JP5787683B2 (en) * | 2011-09-13 | 2015-09-30 | 株式会社トクヤマ | Method for producing aluminum nitride sintered granules |
| EP3916068B1 (en) * | 2014-09-25 | 2024-04-24 | Kabushiki Kaisha Toshiba | Refrigerator comprising rare earth cold accumulating material particles |
| CN111217608A (en) * | 2018-11-24 | 2020-06-02 | 中国科学院宁波材料技术与工程研究所 | Low-temperature sintering method of oxide ceramic |
| WO2023145730A1 (en) * | 2022-01-28 | 2023-08-03 | 株式会社 東芝 | Cold storage material, cold storage material particles, granular particles, cold storage machine, refrigerator, cryo-pump, super-conducting magnet, nuclear magnetic resonance imaging device, nuclear magnetic resonance device, magnetic field application-type single crystal pulling device, helium recondensing device, and dilution refrigerator |
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