JPH0264099A - Production of single crystal of tl-ca-ba-cu-o based high-temperature superconducting material - Google Patents

Abstract

PURPOSE:To stably obtain a single crystal of the subject high-temperature super conducting material with a high critical temperature by specifying the total content of Ca and copper, the contents of Tl and Ba and the atomic ratio of Tl to Ba in the raw material containing Tl, Ca, Ba and copper and treating the raw material using the flux method. CONSTITUTION:Compounds such as Tl2O3, CaO, BaO2 and CuO are mixed to prepare a starting material with 50-80at% (Ca+Cu) composition, 1:1 atomic ratio of Tl to Ba and respectively 10-25at% compositions of Tl and Ba. The resultant starting material is then treated using the flux method, smelted and subsequently kept preferably within the range of 910-860 deg.C for 1-12hr, thus stably obtaining the objective single crystal of Tl-Ca-Ba-Cu-O-based high- temperature superconducting material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a single crystal of a Tl-Ca-Ba-Cu-0 based high temperature superconducting material.

[Prior art] In the T I -Ca-B a-Cu-0 system, CuO and CuO + (Ca, Ba) 0 are similar to the acid 1 arsenide superconducting material in the song.
Attempts have been made to grow single crystals using this as a flux, but it has been difficult to produce them stably.

[Problems to be Solved by the Invention] With conventional raw material compositions, mm-sized crystals with a high Tc, which is called a high-temperature sum, cannot be obtained. This was because the manufacturing conditions were different because the composition in which the high-temperature phase crystallized and the structure formed were unknown.

[Means for Solving the Problems and Their Effects] Therefore, the inventors made strenuous efforts to solve the problems, and as a result, they discovered the manufacturing method described in the claims, which is: ■Crystals. Adjust the blending ratio so that the atomic ratio of (Ca+Cu) in the raw materials used for growth is 50 to 80 at%, the atomic ratio of Tl and Ba is 1:1, and 10 at% to 25 at% ■ Raw material fusion f&910 ~ 1-1 within the temperature range of 860℃
The requirement is to maintain the temperature for 2 hours.

That is, the atomic ratio of the high temperature phase of the Tl-based superconductor is Tl:Ca:
Ba:Cu=2:2:2:3, but in order to grow a single crystal by the flux method, it is necessary to further add a flux material to the composition ratio of 2223 as a raw material.The inventors used this as a flux material.

(CaO+Cu0) was used, and the amount added was optimized.

The results are shown in Figure 1, with Tl:Ca as the raw material.
It has been found that a crystal having the highest Tc can be obtained when :Ba:Cu=2:6:2:6.

This is because this composition ratio is exactly within the composition range in which high-temperature phase crystals crystallize. In addition, (Ca+Cu) is 50 to 80
Even with other compositions within the at% range, after melting the raw materials, the
It has been found that the formation of a high temperature phase progresses by holding the sample at a temperature of 1 to 12 hours. This is because the high temperature phase is generated by a peritectic reaction within the above temperature range. Although the holding time varies depending on the composition ratio and temperature, a reaction time of about 1 hour is required at 900°C, and about 12 hours at around 860°C.

[Example] Tc (K) at each raw material composition ratio was as follows. Namely.

Raw material composition ratio Tc (K)Tl:Ca
:Ba:Cu 2 3 2 3.75 114-1152 4
2 4.5 115 2 5 2 5.25 118 2 7 2 6.75 115 2 8 2 7゜5 94 At the above composition ratio, T 1203, CaO, BaO2, Cu
The raw material was prepared by mixing O and forming pellets at about 1 to 2 tons/cm. The raw material has an inner diameter of 10 to 12 m.
The material was sealed in an Au pipe of mφ, and the Au pipe was further inserted into a p-type crucible and placed in a furnace to grow crystals. The growth conditions are as shown in FIG. The inside of the furnace had an O2 gas flow of 200 to 500 m1/min, and the raw material charge amount was 2 to 5 g. Crush the cooled tIiI material
When the crystal was taken out from the flux, the crystal was 0.5
A sample with a mouth size of ~2.5 mm was obtained. These crystals are DC magnetized 4! When Tc was measured, it was 10
Crystals with various Tc's from 8 to 120 were obtained. Among these, crystals exhibiting a Tc of 118 to 120 are 0.5 to 1.
9 [Effects of the present invention] Until now, the low T of Tl-Ca-Ba-Cu-0 based superconductors
Previously, only c-phase single crystals could be obtained, but with the present invention, it is now possible to stably obtain mm-sized large single crystals with a high temperature sum (Tc = 118 to 120 K>), which greatly expands the scope of industrial implementation. The effects that spread over the world are extremely large.

[Brief explanation of the drawing]

Claims (2)

[Claims] (1) When producing a single crystal of an oxide superconducting material containing Tl, Ca, Ba, and Cu as constituent elements by a flux method, the composition of (Ca+Cu) in the starting material is 50 at.
% to 80 at%, the atomic ratio of Tl and Ba is 1:1, and 1
Tl-C characterized by being 0 at% to 25 at%
A method for producing a single crystal of a-Ba-Cu-O based high temperature superconducting material. (2), 1 within the temperature range of 910-860℃ after melting the raw material.
Tl-C according to claim 1, which maintains the temperature of the raw material for ~12 hours.
A method for producing a single crystal of a-Ba-Cu-O based high temperature superconducting material.