JPH01301521A - Ceramic-based electrically conductive material - Google Patents

Abstract

PURPOSE:To obtain the title nontoxic material of high environmental resistance with broad applications, by adding a specified amount of Pb to a Bi-M(Ca, Sr, Ba)-Cu-O-based superconducting product followed by calcination at specified temperature to attempt single phase formation at high critical temperature. CONSTITUTION:A Bi-M-Cu-O-based superconducting material (M is combination of plural elements selected from Ca, Sr and Ba) is spiked with Pb so as to be 0.006-0.08 in atom ratio Pb/Bi and calcined in an oxygen atmosphere at 500-810 deg.C. The resulting product is put to compression forming followed by sintering and annealing, thus obtaining the objective material. According the above process, separation of a low critical temperature-phase can be suppressed, leading to establishing stabilized superconducting phase, thereby accomplishing high critical current density and high critical magnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ceramic conductive material used in Josephson elements, superconducting motors, superconducting magnets, and the like.

(Prior Art) Ceramic conductive materials (superconducting materials) that have a critical temperature higher than the liquid nitrogen temperature are broadly classified into Houst materials.

Y-Ba-Ca- discovered by C, W, Chu et al. of n University
0 series, the B1-8r-Ca-Cu-0 series discovered by Mae et al. of the National Institute of Materials Science and Technology, and the Tl-Ca- series discovered by A.M. Hermann et al. of the University of Arkansas.
There are three types of Ba-Cu”O type.For details of these material properties, please refer to Physical Review Letter
r, Vol.

58, No, 9. p 908-. 910
．． 1987, N1kkei EleCtrOniC
8 April 18, 1988 (No. 445) p175 and Nature (London) No. 332. p55
゜1988, etc.

(Problem to be solved by the invention) However, the Y-Ba-Cu-0 system of conventional superconducting materials has poor environmental resistance because it is easily hydrolyzed, and rare earth elements are produced in uneven regions (Japan does not produce them). ), B1-8r
-Ca-Cu-0 system is difficult to create a single phase (high critical temperature phase and low critical temperature phase are mixed, and the high critical temperature phase becomes less than 50%, causing a decrease in critical current density and critical magnetic field), Tl- Ca
-Ba-0 series had problems such as high toxicity.

In particular, its easy hydrolysis and strong toxicity have severely limited its field of application.

The present invention solves these problems and
-The high critical temperature of the Ca-0 system is made into a single phase, and it is non-toxic.
The purpose is to obtain a ceramic conductive material (superconducting material) that has excellent environmental resistance, good quality (single phase), and has few limitations in its application fields.

(Means for Solving the Problems) In order to solve the above problems, the ceramic conductive material of the present invention is l) Bi-M-Cu-0 conductive material (where M is C
combination of multiple elements selected from a, Br, Ba) to p
When b is expressed as P b / B i ratio (atomic ratio), it is 0.
2) Calcination is performed at 8106C or lower.

(Examples) The present invention will be described in detail below according to Examples. First, bismuth oxyacetate, strontium acetate, calcium acetate,
After mixing fine powder of copper acetate, pure water is added and the mixture is stirred and dispersed while heating to 100°C.

Table 1 Basic ratios of Bi, Br, Ca, and Cu are 2:
2: 2: 3, but the amounts of Bi and Cu are adjusted depending on the amount of PB added later.

Next, lead acetate is added to this solution and the final composition ratio after heat treatment (P b
/ B i ) as shown in Table 1 and dispersed again with air.

Note that since Pb easily evaporates during calcination, sintering, and annealing treatments, it is necessary to correct the evaporation amount before adding it. The charging value at this time was 0.05 to 0.5. When the dissolution is almost complete, the mixture is heated to 370° C. to remove moisture and burn off the organic matter. As the water is removed, it gradually becomes clay-like, and when heated further, the organic matter burns and becomes powder-like.

Next, the obtained powder is calcined for 5 hours at 500 to 810 DEG C. in an oxygen cloud atmosphere to obtain a reactant. If the calcination temperature exceeds 810°C, low-melting point compounds may melt and separate (particularly in Kempo, which is more likely to result in fine powder compared to solid-phase reaction methods), or a strong low-critical temperature phase may form, leading to sintering. After compression molding this reaction product, which is undesirable because it becomes difficult to form a high critical temperature phase even if the temperature and annealing temperature are adjusted,
Sintered for 1 hour in an oxygen atmosphere at 8700C, then sintered at 850C for 1 hour.
Annealing treatment was performed at ~855°C for 150 hours to obtain a ceramic conductive material. Sample shape is φ15*L 5
t (mm).

Next, magnetization was measured while cooling this sample to IOK, and the volume ratio of the high critical temperature phase and the low critical temperature phase was determined.

The results are shown in Table 2 together with comparative examples.

The critical temperature phase in the 100 degree range is defined as a high critical temperature phase, and the critical temperature phase in the 60 to 80 degree range is defined as a low critical temperature phase, and is expressed in proportion to the total volume. However, the ratio of phases other than the superconducting phase (the remainder when the total is 100) is a reference value.

As can be seen from the table, the addition of PB significantly increases the number of high critical temperature phases. The addition range is Pb/Bi ratio (
It is preferably within 0.006 to 0.08 when expressed as atomic ratio). If it is too small, there is no effect of addition, and if it is too large, the superconducting phase itself decreases as shown in Comparative Examples 11 and 12, and in addition, excessive addition also reduces the environmental resistance.

Table 2 (%) Also, as mentioned before, if the temperature of calcination exceeds 810℃, a high critical temperature phase will not be formed as shown in Table 3 even if the sintering temperature and annealing temperature are subsequently optimized. It is preferable to carry out the temperature below 810°C.

Table 3: At present, it is unknown which site contains PB, so it is expressed as added.

(Effects of the Invention) As described above, according to the present invention, precipitation of a low critical temperature phase can be suppressed, resulting in a stable superconducting phase, and a high critical current density and high critical magnetic field can be achieved. Furthermore, since it is Bi-based, it is a ceramic-based conductive material that is non-toxic, has excellent environmental resistance, and has few limitations in its application fields. This material can be applied to Josephson elements, electromagnetic wave sensors, magnetic sensors, magnetic flux memories, magnetic shielding materials, power transmission cables, communication cables, superconducting motors, superconducting magnets, etc.

that's all Applicant: Seiko Epson Corporation Agent: Patent attorney Masayoshi Kamiyanagi and 1 other person

Claims (2)

[Claims] (1) Bi-M-Cu-O based conductive material (where M is Ca
, Br, Ba) and Pb
0.006 to 0 when expressed as Pb/Bi ratio (atomic ratio)
．． 1. A ceramic conductive material, characterized in that the ceramic conductive material is added in a range of 0.08 to 0.08. (2) A ceramic conductive material characterized by being calcined at 810°C or lower.