JPH01115864A - Superconductor - Google Patents

Abstract

PURPOSE:To increase critical current density and moisture resistance by adding a specific amount of CaF2 to a sintering type superconductive material of Y2O3- BaO-CuO1-1.2. CONSTITUTION:For example, commercially available Y2O3, BaO and CuO powders are mixed at a molar ratio of 1/2:2:3, formed by pressing, kept at 930 deg.C in an oxidative atmosphere for 24hr, then cooled down at a rate of -50 deg.C/hr. The sintered product of (Y2O3)0.5.(BaO)2.(CuO1-1.2)3 is crushed into fine powder, then 0.3-12.0% of commercially available CaF2 at a weight ratio is added to the powder. The mixture is formed by pressing, then sintered at 880-950 deg.C for 4hr, and the sintered product is treated oxidatively at 750 deg.C for 8hr to give the subject superconductor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to superconductors having superconducting properties at temperatures higher than the temperature of liquid nitrogen.

BACKGROUND OF THE INVENTION In recent years, superconductors with high critical temperatures have been discovered one after another, and a material having superconducting properties at the temperature of liquid nitrogen has finally been discovered. Among them, especially Y2O,-
Regarding BaO-CuO1-1.2 type superconductors, sintered type and thin film type have been well studied.

When creating a Y2O5-BaO-Cuo, -12 based sintered superconductor by a sintering method, Y2O,, BaO (or B
aC0,) and OuO (or Cu20) powders are thoroughly mixed, pressure molded, sintered at 900-100°C, and slowly cooled, or kept at a fixed point at a low temperature for a long time. The properties are improved through low-temperature oxidation treatment.

Problems to be Solved by the Invention However, it is difficult to obtain a high critical current density with the sintered superconductor manufactured by the method described above, and furthermore, it has extremely poor moisture absorption characteristics and does not easily react with moisture in the atmosphere. The superconducting properties deteriorated, and it was even possible to see the shape of the sintered body collapse.

In view of the above problems, the present invention provides a Y2O3-BaO-CuO1-1.2-based oxide superconductor that has a large critical current density, excellent moisture resistance, and shows little deterioration in superconducting properties even when left in the atmosphere. It is something to do.

Means for Solving the Problems In order to solve the above problems, the present invention provides Y2O, -Ba
CaF2 is added as an additive in an amount of 0.3 to 12.0% by weight to an O-GuO, ~4.2-based sintered superconducting material.

Effect By employing the above sintering method, the sintered body is densely sintered, oxidation treatment at low temperature is facilitated, critical current density is improved, and moisture resistance properties are improved.

EXAMPLE Hereinafter, a first example of the present invention will be described with reference to the drawings.

Commercially available powders of yttrium oxide (Y2O3), barium oxide (BaO), and cupric oxide (CUO) were prepared as follows: rnol: 2 mol: 3 rno
After mixing at a ratio of 1.1 and pressure molding,
The temperature was maintained at 0° C. for 24 hours and then cooled at a rate of −60° C./hour to obtain a sintered body.

(Y2O5)l15 meeting (Bad)2-(C
ubl-,,2).

A sintered body of 0.30 to 12.
0% commercially available calcium fluoride (caF2) t: Added, mixed, pressure molded, sintered at a temperature of 880 to 950°C for 4 hours to obtain a sintered body, then heated at 750°C for 8 hours. It has been subjected to oxidation treatment. Next, silver electrodes were burned onto these sintered bodies at low temperatures. In addition, the shrinkage rate of such a sintered body by sintering is 880' when 3% by weight of CaF2 is added.
3% by firing C.

5% when fired at 910'C (7), 1 when fired at 9ESO"C
It was 0%. The critical current density and moisture resistance properties of the samples thus prepared were measured.

FIG. 1 shows an element for evaluating the characteristics of a sintered superconductor in a first embodiment of the present invention.

In FIG. 1, 11 indicates a sintered superconductor, and 12 indicates a silver electrode. The superconductor 11 has a thickness of about 4.0 wings.

The diameter is about 13. It has a disk shape of Onφ.

A low-temperature baking type material was used for the silver electrode material.

Using the above-mentioned device, we measured the properties of superconductors.

Figure 2 shows (Y2O3)0. -(Bad)2- ((j
uO,−,,2), the amount of CaF2 added to 5 (wtC
It is a figure showing the relationship between X) and critical part 1i ('K).

For comparison, the figure also shows the characteristics of a material to which no CaF□ was added. From FIG. 2, it is recognized that when the amount of CaF2 added exceeds 12%, the critical temperature decreases rapidly.

Figure 3 shows (Y2O, >1lL5e (Bad)2@(C
The amount of CaF2 added to uO1~1.2)3 (
%) and critical current density (mu/ff1). The critical current density is (if the addition l of aF2 is 3w
Maximum near t%, sono value is JC ~ 1oom/cI
! It is observed that when the amount of L added is 12 wt% or more, it decreases rapidly.

Figure 4 shows (Y2O3)CL5°(B″0)2°(Cub
lt2) system sintered body at 40'C, relative layer fta o~
This figure shows the change over time in the outer diameter of the sintered body when it was left in a 95% atmosphere. In the figure, 14 shows an example of a conventional material in which CaF2 is not added, 16 shows an example in which the amount added is 0.3 wt%, 18 id: 3 W tcX
, 1 The case of 12 wt%O is shown. From FIG. 4, in the sintered body to which CaF□ was added, the change over time in the outer diameter of the sintered body due to humidity was small, and the effect of adding CILF2 was observed.

When the amount of CaF2 added is 12 wt% or more, the outer diameter hardly changes.

FIG. 5 shows the change over time in the resistance value of the sample at room temperature when the sample was left in an atmosphere of 40'C and relative humidity of 90 to 95%. The change in resistance value over time is extremely large, and the structure of the sintered body itself seems to be changing. These samples have semiconductor properties at room temperature and become superconductors at low temperatures, but the critical current density at superconductivity is closely related to the electrical resistance of the semiconductor at room temperature. That is, the change in resistance value over time at room temperature is mainly due to decomposition and precipitation of foreign substances, and these are considered to have a direct effect on the critical current density in superconductors. Ca
Although the addition of F2 slightly stabilizes the change in resistance value at room temperature over time due to humidity, it was not possible to completely stop this change.

In addition, in FIG. 6, 14 shows an example of a conventional material in which CaF2 is not added, and 16 shows an example of a conventional material in which the amount of addition is 0.3 wt%, 1
6 is 3wt%, and 1% is 12wtCX.

A second embodiment of the present invention will be described below.

Commercially available powders of Y2O3, BaO and CuO were prepared by -;no/: 1.2tsmo, d: 1. ts9
After mixing in a mol ratio and molding under pressure, it was heated to 950' in the atmosphere.
24 hours of firing at C, then hourly -so'c
(Y2O3), 5- (BaO), 4
A sintered body having a composition of 5s (CuO1-12), .59 was obtained. Next, this sintered body is finely pulverized and the weight ratio is 0.3 to 12.
．． Pressure molded with 0% CaF2 added, 890-96
After firing at a temperature of 0°C for 4 hours, oxidation treatment was performed for 750'CB hours.

When 3% CaF 2 was added, the shrinkage rate was 3% when fired at 890°C, ts9c when fired at 1920°C, and 10% when fired at eeo°C.

Using the thus prepared sample, critical current density and moisture resistance were measured.

The critical current density showed almost the same tendency as in the first example, and when CaF 2 was not added, Jc ~ 22 μm/Cnl
increases with the addition of CaF2, reaches a maximum of %Jc~36 μm/d when the amount of CaF2 is added, and decreases as the amount added is further increased. The critical temperature shows a tendency similar to that of the first example, and when the amount of CaF2 added exceeds 14%, it becomes lower than the temperature of liquid nitrogen.

The expansion of these samples due to humidity can be suppressed by adding CaF2, which is almost the same as in the first example, and the change in resistance value over time in humid air at room temperature is still similar to that in the first example. The same trend was observed.

A third embodiment of the present invention will be described below.

-mop of commercially available powders of Y2O5, BaO, and CuO, respectively: 4. s mol: s, o rno
Mix at a ratio of 1/2.

After pressure molding, it was fired in the atmosphere at 940°C for 24 hours, and then cooled at a rate of -50'C per hour (Y2
O3) 0.5m (BaO), 45 fist (Cu01-
A sintered body having a composition of 1, 2) and 5 was obtained. Next, this sintered body was finely pulverized, CaF2 of 0.3 to 12.0 weight ratio was added thereto, and the mixture was press-molded.

After 4 hours of baking at a temperature of 880-960°C.

Oxidation treatment was performed at 760°C for 8 hours. CaF2 3
%, the shrinkage rate is 3% when fired at 880°C.
6 for firing at 910″C, 10% for firing at 960°C
Met.

Using the thus prepared sample, critical current density and moisture resistance were measured.

CaF 2 3 N addition (20s
)as” (BaO)(L45.

(CuO, ~t2) The critical current density was maximum in the 5-based sintered body, and the critical current density was Jc~43 μm/cIit in one shift. The dependence of the superconducting property on the amount of CaF 2 added, the temporal change in the outer diameter of the sample due to humidity, the deterioration of the critical current density due to humidity, etc. showed almost the same trends as in the first example. When the amount of C&F 2 added exceeds 13, the superconducting properties above the liquid nitrogen temperature are lost.

A fourth embodiment of the present invention will be described below.

Commercially available powders of Y2O3, BaO, and CuO were prepared with -mol: 2.76rnol: e, 2tsm, respectively.
After mixing at a ratio of
K for 24 hours, then hourly −s o '
c at a rate of (Y2O3)a5.(BaO+2.
A sintered body having a composition of 75'(Cu',-12' 6.25) was obtained. Next, this sintered body was finely ground to give a weight ratio of 0.75'(Cu',-12').
3-12. Add CaF2 to
After firing for 4 hours at a temperature of 0 to 960℃, 750℃
Oxidation treatment was performed for 8 hours.

When three parts of CaF2 were added, the shrinkage rate was 3% when fired at 870°C, 6% when fired at 910°C, and 10% when fired at 950°C.

Using the thus prepared sample, critical current density and moisture resistance were measured.

When 3% CILF2 was added (Y2O3), 5m
(Bai)2. ,, e(CuO, ~1.2) &2s
The critical current density is maximum in the system sintered body, and its value is Jc
~68 mu/cT&. The dependency of the superconducting property on the amount of CaF2 added, the change over time in the outer diameter of the sample due to humidity, the deterioration of the critical current density due to humidity, etc. showed almost the same trends as in the first example. When the amount of CaF2 added exceeds 16%, superconducting properties at temperatures above the liquid nitrogen temperature are lost.

A fifth embodiment of the present invention will be described below.

Commercially available Y2O, BaO, and CuO powders: nol: 0.75 mol: 2.09rn
After mixing at a ratio of O1 and molding under pressure, it was heated to 930'C in the atmosphere.
Calcination was carried out for 24 hours at
A sintered body having a composition of "(C"j-12'2.0?) was obtained.

Next, this sintered body is finely pulverized, and the weight ratio is 0.3 to 12.0.
% CaF2 was added and pressure molded at 880-950℃.
After firing at a temperature of 4 hours, oxidation treatment was performed at 760'C for 8 hours.

When CaF2 is added at 3%, the shrinkage rate is 35< when fired at sso'c, 6% when fired at 91o'c, and 960°C.
In the case of firing, it was 1*%.

Using the thus prepared sample, critical current density and moisture resistance were measured.

When 3% of CaF2 is added (Y2O,)llL,,e
(B2LO), 5-(CuO, ~1.2h09
The critical current density is maximum in the system sintered body, and its value is Jc
~38 μm/CIi. The dependency of the superconducting property on the amount of CaF2 added, the change over time in the outer diameter of the sample due to humidity, the deterioration of the critical current density due to humidity, etc. showed almost the same trends as in the first example. When the amount of CaF2 added exceeds 13%, superconducting properties at temperatures above the liquid nitrogen temperature are lost.

As examples above, six types of Y2O3-
The effect of CaF2 addition on the critical current density and humid air deterioration characteristics of BaO-Gum,~,2-based compositions has been shown, but the effect of CaF2 addition is not limited to these six types of compositions, and can be expressed in terms of molar ratio. The four compositions (Y2O
,)cL5- (Bad) tzs-(Cub,-,
2) 159° (Y2O3), 5-(BaO)45- (
Cub, -, 2)5. (Y2O3)0.5-(BaO
)2.75- (Cubl-,,2),5 and (Y2O
3) 0.5-(BaO)Il, 5* (CuO4-1,
2) Covers the entire superconducting composition surrounded by 2.09. 6th
The figure shows the range. In Figure 6, 1
is (Y2O,). . 5-(BaO)2-(CuO,-
,,2) 3.2 is (Y2O3), -(Bad) t2
5-(OuO1~1,2), 52.3 is (Y2O,)c
L5- (Bai), -(CuO1-t2)5, 4
is (Y2O3)0.5- (B2LO) , 5・(C
uO+-tz) tzs + s is (Y2O,)CL5-
(Bad), 5-(Cu01-1.2)2.09
The reason why we limited the superconductor to a superconductor made by adding CaF2 to the composition surrounded by the above four compositions of 0conoY2O5-BaO-Cub and -12 systems is that good critical current density can be obtained with materials within this range. However, outside this range, this becomes small and is not suitable as a superconductor. Also, Y2O3-
The amount of CaF2 added to the BaO-Cub, -12 composition is 0.3 to 12. Owt9c was limited to 0.
This is because if the addition is less than 3%, a sufficient addition effect will not be exhibited, and if it is more than 12.09c, the critical temperature will be below the liquid nitrogen temperature, reducing the merits as a high-temperature superconductor.

Effects of the Invention As described above, according to the present invention, four compositions (τ20s) as e (BaO+, 25
- (CuO1-1.2),. 59°(Y2O3)0.
5- (Bad), 5m (Cub, -12)5. (
Y2O3)0.5#(BaO)2.75-(CuO,
-12), 25. and (Y2O5)TL5”(BaO)
Il, 5-(Cu01~tz)2. 0.3 to 12.0% by weight of CaF2 in the composition within the range surrounded by C9
By adding it to create a sintered superconductor, the effect of improving critical current density and moisture resistance properties can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an element for evaluating the characteristics of a sintered superconductor in the first embodiment of the present invention, and FIG. 2 is a characteristic diagram showing the critical temperature of the same superconductor with respect to GaF2-added glass. Figure 3 is a characteristic diagram showing the critical current density with respect to the amount of C1LF2 added to the same superconductor, Figure 4 is a characteristic diagram showing the change in shape of the same superconductor over time when left in humidity, and Figure 6 is a characteristic diagram showing the change in shape of the same superconductor when left in humidity. Fig. 6 is a characteristic diagram showing the change in electrical resistance over time due to regular storage, and Fig. 6 is a composition diagram showing the compounding composition of the Y2O, -BaO-Cub, 2 system of the superconductor according to the embodiment of the present invention. . 11...Superconductor, 12...Silver electrolyte. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 4
Between the images (HF) Fig. 5 Fig. 6 τY20t

Claims (2)

[Claims] (1) Y_2O_3-BaO-CuO_1_~_1_.
CaF_2 is added to the _2-based sintered superconducting material at a weight ratio of 0.
．． A superconductor characterized by adding 3 to 12.0%. (2) Y_2O_3-BaO-CuO_1_~_1_.
As a _2-based sintered superconducting material, there are four compositions expressed in molar ratio (Y_2O_3)_0_. _5・(BaO)_1_. ＿
2_5・(CuO_1_〜_1_._2)_1_. ＿５
_9, (Y_2O_3)_0_. _5・(BaO)_4
＿． _5・(CuO_1_〜_1_._2)_5, (Y
_2O_3)_0_. _5・(BaO)_2_. ＿７＿
5・(CuO_1_〜_1_._2)_6_. _2_5
and (Y_2O_3)_0_. _5・(BaO)_0_
．． The superconductor according to claim 1, using a composition within the range surrounded by _7_5·(CuO_1_ to_1_._2)_2.