JPH0244028A - Bi-pb-sr-ca-cu-o superconducting material - Google Patents

Abstract

PURPOSE:To obtain a superconducting material high in superconducting critical temp. by using Bi-Pb-Sr-Ca-Cu-O type oxide having a specified molar composition. CONSTITUTION:Pb is incorporated into a Bi-Sr-Ca-Cu-O superconducting material and the molar ratio of Bi:Pb:Sr:Ca:Cu is regulated to (0.8-2.2):(0.01-1.5):(1.5-2.2):(0.8-2.2):(0.01-4). Bi2O3, SrCO3, CaCO3, CuO and PbO are used as starting materials and mixed in a desired ratio and this mixture is directly heated to produce a superconductor. An oxalate precipitating method may be adopted. Since Pb is used, production is facilitated and the superconducting critical temp. is raised to 77-105K.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has recently attracted attention as it has the potential to exhibit superconductivity at temperatures above 77, which is the boiling point of liquid nitrogen, and in some cases even at higher temperatures, above 100. old-3r-Ca-Cu-0
The present invention relates to a superconducting material containing PB.

[Conventional technology]

Recently, the Institute of Metals Research has found that the electrical resistance of a sintered body with a composition of Bi, Sr, and Ca1Cuz begins to decrease at 120K, and after rapidly dropping to about 107K, the electrical resistance reaches zero at about 75K. There was an announcement that it would happen.

According to this announcement, this material has a superconducting transition end point at which the electrical resistance becomes zero: a superconducting phase (for high Tc) at about 105 K (value obtained by extrapolating from experimental pigs) and a superconducting phase (for high Tc) at about 75 K. Although it is said that there are two types of superconducting phases (low Tc phase) and the whole is not a complete high Tc sample, the Meissner effect is observed in this material. Met.

Additionally, this material is a superconducting material that does not contain rare earth elements.
It was also reported that it is more stable in water and the like than the Y-Ba-Cu-0 system.

After this announcement, follow-up tests were held not only in Japan and the United States, but also in other countries around the world. Examples of such tests are as follows.

In other words, inorganic materials research, etc.! 3+z (Ca, Sr)
3CLIZO9 or Biz (Ca, Sr)z-xCL
It was announced that the electrical resistance of a sintered body having a composition of IzOll-y starts to decrease at about 110 and becomes zero at about 70 to 40.

Problems to be solved by the invention] Most of the Bi-Ca-3r-Cu-0-based materials currently announced have a mixture of high Tc phase and low Tc phase,
Their chemical composition also varies.

Further, according to additional tests conducted by the present inventors, this substance does not become a high critical temperature substance unless it is treated at a heat treatment temperature close to the melting point of the sample, and the synthesis conditions are extremely limited. It's clear.

In order to overcome such drawbacks, the present inventors have developed B1-Sr-
Through repeated research such as adding PB to the Ca-Cu-0 system, varying the composition ratio of the component elements, and varying the heat treatment conditions, the superconducting critical temperature was at least higher than the boiling point of liquid nitrogen, 77, depending on the conditions. They succeeded in synthesizing a substance that reaches a temperature of 105 K or higher, leading to the present invention.

[Means to solve the problem]

That is, the present invention is based on Bi+Sr+ announced by the Institute for Metal Materials.
The purpose is to provide a material in which Ca+Cu20x contains Pb, and in addition to this, a material in which the composition ratio of each constituent element is changed.More specifically, B1-PbSr
It is a Ca-Cu-0 based oxide, and the constituent element is Bi.

The molar ratio of Pb, Sr, Ca, and Cu is old n+
Pb1I, Sr, , Cay, Cuz (n, m,
x, y, z are 0.5< n <2.6, 0°O1≦
m≦1.5.1.5≦x≦2.2.0.8≦y≦2.2
．． old-Pb expressed as 2.0≦2≦4.0)
-Sr -Ca-Cu-0 based superconducting material, B1-Pb-Sr having a superconducting critical temperature of at least 77°C
-Ca-CuO based superconducting material is provided.

In this way, the present invention incorporates Pb into the conventional old-3r-Ca-Cu-0 system, but in this case, if the content of Pb, that is, the m value is larger than 1.5, the material becomes a semiconductor. On the other hand, if it is smaller than 0.01, the substance will not be much different from the conventional one in which no PB is added.

The above compound can be produced by the method described below.

That is, BizO:+, SrCO3, CaCO as raw materials
3. Using CuO and PbO as starting materials, weigh and mix each in the desired ratio, or use Bi, Pb, Sr, Ca
, Cu, and oxalate containing each of them in a desired ratio is synthesized by a precipitation method. At this time, Bi, Sr, Ca, and Cu may be added at desired composition ratios, but since PB is lightly emitted during the heat treatment performed later, it is necessary to add Pb so that the composition ratio is equal to or higher than the intended composition ratio.

These mixed powders or oxalate are heated in air at about 800°C to perform a solid phase reaction, but when heating oxalate, thermal decomposition is carried out at about 250°C, and then at about 800°C. It is preferable to carry out a heating reaction. Then crush it to about 1
After pressurizing at 000 kg/cnl to form a pellet, it may be further fired at 810°C to 880°C.

Hereinafter, the relationship between the properties of the produced B1-Pb-Sr-Ca-Cu-0 based superconducting material, the ratio of the number of moles of the constituent elements, and the manufacturing process conditions will be explained in more detail.

First, the superconducting critical temperature of the produced superconducting material is greatly influenced by the ratio of the number of moles of the constituent elements. 2 Cu
If the range of the ratio of the number of moles of other constituent elements is shown as 13
i0.7-wl, 2 Pbo, o4-o, z Sr
+, ow+-3Ca1. Osb + -z Cu2 is a preferred range, and superconducting materials in this range have a high probability of achieving superconducting critical temperatures of 100 or higher.

Next, regarding the manufacturing method, in manufacturing the superconducting material according to the present invention, there are two cases in which the raw material powders are mixed as they are and adjusted to a predetermined composition ratio, and two cases in which oxalate, citrate, etc. are prepared in a predetermined composition ratio by a precipitation method. Compared to the case of precipitating and preparing as a carboxylate salt of It's also easy to get what you're looking for.

〔Example〕

Example 1 BizO:+, PbO, SrCO3, C as raw material powder
The molar ratio of the constituent elements of aCO3 and CuO is Biz, 0+
pbo, 6+ Srz+ Caz+Cu3. , and after thoroughly mixing and pulverizing it in a mortar,
The mixture was placed in an alumina boat, and a solid phase reaction was carried out in an electric furnace at 800° C. for 24 hours in the air to obtain a black powder.

After thoroughly mixing and pulverizing this powder in a mortar, approximately 1,000
Approximately 1 cm in diameter and 1 m in thickness with a press of kg/c+a
m green compact pellet and heat it at 845°C to 143°C.
It was heated and fired in air in an electric furnace for an hour. The results of analyzing the molar ratio of the constituent elements of the sample after firing using ICAP (
Results normalized by the number of moles of CU) Bit, wa
+ PbO, IIl+ Sr2. OO+Cat,
9b+ Cu3.60.

The temperature change in electrical resistance of this material is as shown in FIG. As is clear from this figure, the electrical resistance of this material is 1
It started to fall by 20, and it suddenly fell by 115, and about 1
05, and it was recognized that this material has extremely excellent superconducting properties.

In addition, the Meissner effect measurement results are as shown in Figure 2.
It was confirmed that a superconductor becomes a superconductor when the temperature is about 105 or more.

Furthermore, this material was a sintered body with sufficient mechanical strength for practical use.

Example 2 The firing time at 845° C. in Example 1 was extended to 244 hours, and the other procedures were the same. As a result of analyzing the composition of the sample after firing by ICAP (normalized by the number of moles of Cu), the composition was aftowar Pb
o, +o+ SrZ, 00+ Ca1. qa* CL1
It was 3.60.

The temperature change in electrical resistance of the material obtained in this example is as shown in FIG. As is clear from this figure, the electrical resistance of this material begins to drop at 115, rapidly drops at 110, and reaches zero at about 107, confirming that this material has extremely excellent superconducting properties. .

Example 3 BizOz+PbO, SrCOz, Ca as raw material powder
C0:+ and CuO, the chemical composition ratio after firing is old 1
．． 2+ Pt11. Z*Srz+ Ca1n Cu3
．． After thoroughly mixing the mixture in a mortar and a mortar, the mixture was placed in an alumina boat and heated at 800° C. for 24 hours in an electric furnace in air for solid phase reaction to obtain a black powder. After mixing and pulverizing this black powder in a mortar again, approximately 1000 kg
A green pellet having a diameter of about 1 cm and a thickness of about 1 mm was formed by pressing at g/cA, and the pellet was fired in air at 845° C. for 48 hours. IC about the sample after firing
Results of composition analysis by AP (normalized by number of moles of Cu) lli+, +z+ Pbo, q4+
Sr1. a6+ CaI.

It was 90+ Cub, Z.

The temperature change in electrical resistance of this material is as shown in FIG. As shown in the figure, the electrical resistance suddenly drops at about 120 and becomes zero at about 90.

Furthermore, the Meissner effect and mechanical strength of this material showed substantially the same results as in Example 1.

Example 4 Ammonium oxalate was added to a mixed aqueous solution of nitrates of Bi, Pb, Sr, Ca, and Cu, and the composition ratio of the component elements was adjusted to old r, qz+ Pbo, as+ Sr2.0+
Ca2.0+ ct13.2 oxalate was precipitated, dried at 100°C, heated at 250°C, and then heated to 800°C.
A black powder was synthesized by heating in air in an electric furnace for 24 hours. This was re-pulverized and mixed, pressed at approximately 1000 kg/cm'' to form a green pellet with a diameter of 1 cm and a thickness of 1 bar, and then heated and fired in air at 845°C for 48 hours in an electric furnace. I CAP analysis results (normalized by the number of moles of Co) B' 1. eat
PbO* ZO+ S'2-00+Cal, q6 Cu
3. As shown in Figure 5, the temperature change in the electrical resistance of this object suddenly dropped from about 120 to about 105.
It became zero. Furthermore, the Meissner effect and mechanical strength of this material showed substantially the same results as in Example 1.

Example 5 In the same manner as in Example 4, the composition ratio of the component elements was set to Bio,
tz+ Pb1har Srz, Or Ca2. Or
Cu3.2 \old 2.12+Pbo, z4+ Srz,
z+ C7) z, z+ C113,2 or old 1.71
Pb6゜:ll Sr2.0+ ca,, 0+ C
The oxalates of u:+ and o were precipitated, respectively, and baked pellets were synthesized in the same manner as in Example 4. IC of these samples
The analysis results by AP (results normalized by the molar ratio of Cu) are, in order, Bfo, z Pb1.14 S
r+, qa CaI,, 6Cui, z, old z, orl
Pbo, +z Srz, +q Ca2.16 Cu=,
z, Bit, t Pbo.

+ o Srz, o Cao, 9'7 C1l:1
．． It was o.

Among these, the temperature change in the electrical resistance of the first substance, as shown in Figure 6, falls at about 120 and becomes zero at about 85, and the same was true for the second and third substances. .

In addition, the Meissner effect and mechanical strength of this substance were determined in Example 1.
The results were almost the same as in the case of .

Example 6 Ammonium oxalate was added to a mixed aqueous solution of nitrates of Bt, pb, Sr, Ca, and Cu so that the composition ratio of the component elements was BI +, 921 Pbo, 4B + Sr
2. O+ Caz, O+ Cu3. The oxalate of Z was precipitated, dried at 100°C, heated at 250°C, and then heated in air at 800°C for 24 hours in an electric furnace to synthesize a black powder. This is re-pulverized and mixed to produce approximately 1000 kg
/cm2 press to form a green pellet with a diameter of 1 cm and a thickness of 1 mm, and then heated in an electric furnace at 835"C for 92 hours.
Fired in air. Results of analyzing this sample with ICAP (results normalized by the number of moles of Cu) Bj+-
82+ PbO0O1l+ Srz, OO+(:al
, qo cui, zo.

As shown in FIG. 7, the temperature change in electrical resistance of this product dropped sharply at about 120°C and became zero at about 107°C.

The X-ray diffraction diagram of this product, as shown in Figure 8, showed that the high temperature phase accounted for 90% or more. Furthermore, the Meissner effect of this material was confirmed as shown in Figure 9 (the high temperature phase was approximately 95% or more).

Example 7 Ammonium oxalate was added to a mixed aqueous solution of nitrates of old, Pb-+ Sr, Ca, and Cu, and the composition ratio of the component elements was Bi+, qz+ Pb0.4B+ Srz, o
+ CaZ, O+ Cux, oxalate of z is precipitated, dried at 100°C, heated at 250°C, and then heated to 800°C.
A black powder was synthesized by heating in air in an electric furnace for 24 hours. This is re-pulverized and mixed to approximately 1000 kg/cm2
This was pressed into a green pellet with a diameter of 1 cm and a thickness of 1 nm, and this was fired in air at 830° C. for 72 hours in an electric furnace. The results of analyzing this sample with ICAP (
Results normalized by the number of moles of Cu) Bt l+
'lo+ l'bo, 2G+ Srz, o.

Ca1. It was q6 cu3.20.

The temperature change in electrical resistance of this product dropped sharply at about 120°C and became zero at about 107°C. The X-ray diffraction diagram of this product is shown in Figure 10, and the high temperature phase was about 95% or more. Furthermore, the Meissner effect of this substance showed substantially the same results as in Example 6.

Example 8 Ammonium oxalate was added to a mixed aqueous solution of nitrates of Bi, Pb, Sr, Ca, and Cu so that the composition ratio of the component elements was Bl 1.4+ Pbo, 6+ Sr2. O+
"a2-0+ CCl2-6 oxalate is precipitated, dried at 100"C, heated at 250°C, and then heated to 800°C.
A black powder was synthesized by heating in air in an electric furnace for 24 hours. This was re-pulverized and mixed, pressed at approximately 1000 kg/cm'' to form green pellets with a diameter of 1 (1 mm) and a thickness of 1. mm. Results of analyzing the sample with ICAP (C
Results normalized by the number of moles of u) Bi+1+ r
'bo, oq+ Sr1.96+ Cal, q. C.U.
3. It was ha.

The temperature change in electrical resistance of this material is approximately 120 >, m
It fell to zero at about 107. As a result of the X-ray diffraction diagram and Meissner effect measurement of this product, the high temperature phase is approximately 95%.
It was recognized that some amount of

〔Effect of the invention〕

The Di-Pb-Sr-Ca-Cu-0 based material according to the present invention is a superconducting material having a superconducting critical temperature at least above the liquid nitrogen boiling point of 77, and an even higher critical temperature of 105.

The manufacturing method for this substance is easy as described above, and especially when using the precipitation method, as described above, the reproducibility of the manufacturing method is high,
It also has the characteristic that it is easy to obtain a target product with a high ratio of high Tc phase.

[Brief explanation of the drawing]

FIG. 1 is an electrical resistance-temperature correlation diagram of the material obtained in Example 1, and FIG. 2 is a complex magnetic susceptibility-temperature correlation diagram of the same material. FIG. 3 shows the material obtained in Example 2, and FIG. 4 shows the material obtained in Example 3.
FIG. 5 is an electrical resistance-temperature correlation diagram of the material obtained in Example 4, and FIG. 6 is an electrical resistance-temperature correlation diagram of the material obtained in Example 5. FIG. 7 is an electrical resistance-temperature correlation diagram of the material obtained in Example 6,
FIG. 8 shows an X-ray diffraction diagram of the material obtained in the same example, and FIG. 9 shows a complex magnetic susceptibility-temperature correlation diagram of the material obtained in the same example. FIG. 10 is an X-ray diffraction diagram of the substance obtained in Example 7. R/R (300K) Ro (blind body X (left hand vs. side)

Claims (1)

[Claims] (1) A Bi-Pb-Sr-Ca-Cu-O based oxide, in which the molar ratio of constituent elements Bi, Pb, Sr, Ca, and Cu is Bi_n, Pb_m, Sr_x, Ca_y, and C
u_z (n, m, x, y, z are 0.5<n<2.6, 0
．． 01≦m≦1.5, 1.5≦x≦2.2, 0.8≦y
≦2.2, 2.0≦z≦4)
-Pb-Sr-Ca-Cu-O based superconducting material.