DD297389A5 - PROCESS FOR PREPARING POLYCRYSTALLINE OXIDIC HIGH TEMPERATURE SUPERVELITUDE OF MATERIALS - Google Patents

Abstract

The invention relates to the field of electrical engineering / electronics and relates to a process for producing polycrystalline oxide high-temperature superconducting materials, the z. B. come as a superconductor used. The object of the invention is achieved by a process for the production of high-temperature superconducting materials, in which a pulverfoermiges precursor is produced and deformed by thermal or chemical means, anschlieszend up to or just above the temperature of the partial, incongruent melting of the starting materials in oxygen or heated in an oxygen-containing atmosphere, but without reaching a homogeneous melt, kept at this temperature and then cooled until complete solidification, according to the invention dissolved in that the heating is carried out under Mikrogravitationsbedingungen and the subsequent process steps can be carried out under Mikrogravitationsbedingungen. By means of the invention it is possible to produce superconductors with improved properties {electrical engineering; Electronics; HTSC; superconductors; Shaped bodies, thermal, chemical; primary product; Oxygen, oxygenated; Microgravity}

Description

The invention relates to the field of electrical engineering / electronics and relates to a process for the production of polycrystalline oxide high-temperature superconducting materials, the ζ. B. come as a superconductor used.

Characteristic of the known state of the art

From a powder mixture of the starting materials or from pre-reacted intermediates, a shaped body is produced. This shaped body is subjected to a heat treatment, which depends on the particular desired chemical composition in terms of time and temperature. The temperatures range from 860 ° C to 960 ° C. The sintering times are usually several hours to days. During this heat treatment, the high-temperature superconducting compound forms and is simultaneously sintered (for example, Chen et al., Rev.Sei.Items 58 [1987] 1565; Tarascon et al., Phys. Rev. B 38 [1988] 8885) ).

For high-temperature superconductors special composition is advantageously a post-treatment in oxygen at temperatures of 25O ⁰ C to 38O ⁰ C performed (DD275787).

The disadvantage of this method is that there is insufficient sintering and / or the formation of areas of disturbed composition at the grain boundaries.

Object of the invention

The object of the invention is to achieve an improved sintering of high-temperature superconducting materials and / or to reduce the formation of regions of disturbed composition at the grain boundaries of high-temperature superconducting materials.

Explanation of the essence of the invention

The invention has for its object to prevent the increase of partial melting during the production of high-temperature superconducting materials.

The object of the invention is achieved by a process for the production of high-temperature superconducting materials in which a powdery precursor is thermally or chemically produced and deformed, then up to or just above the temperature of the partial, incongruent melting of the starting materials in oxygen or heated in an oxygen-containing atmosphere, but without reaching a homogeneous melt, kept at this temperature and then cooled to complete solidification, inventively achieved in that the heating is carried out under Mikrogravitationsbedingungen and the subsequent process steps can be carried out under Mikrogravitationsbedingungen.

embodiments

1. From an intimate mixture of 7.89 g of BaCO ₃ , 9.54 g of CuO and 4.52 g of Y ₂ O ₃ by heating for 24 hours at 900 ⁰ C, which is repeated after crushing and mixing, a powder of YBa ₂ Cu ₃ O ₇ _ _x produced. This powder is comminuted to a mean particle size of 2μιη and pressed in a mold into a ring. The molding is melted air-tight in a reaction tube of quartz glass in the presence of 20OkPa O ₂ , wherein the molding is secured against displacement. The reaction tube is fitted with a protective steel sleeve and transferred to a laboratory under microgravitational conditions. Under conditions of microgravity of 10 ~ ² g _o (g ₀ is the average acceleration of gravity on the earth's surface), the shaped body is heated in an oven for 2 often 98O ⁰ C, with 0.1 K / min to 900 ⁰ C and with 20 K. / min cooled to 350'C. The following is a 20-hour treatment at 350 ⁰ C. After cooling, there is a superconductor ring in front, in which a current flows below 90 K resistance. Critical current densities of 10 ⁵ A / cm ² at 77 K are achieved.

2. A shaped body of YBa ₂ Cu ₃ O ₇ - "is prepared as in Example 1 and sealed in 3in6.fi reaction tube made of quartz glass under 20OkPa O ₂ airtight. The reaction tube is set to ⁰ 92o C, heated in an oven, derzur equipment is part of the payload of a ballistic laboratory. This laboratory is transported on a ballistic path, at the same time the temperature of the molding is increased upon reaching the Mikrogravitationszustandes to 1020 ⁰ C at 80K / min. After holding this temperature for 2 minutes, the cooling is carried out at 50K / min. The molded body is after treatment of the ballistic laboratory 24 each at 92O ⁰ C and at 35O ⁰ C post-treated. It is reached a critical temperature of 92 K and a critical current density of 3 · 10 ⁶ A / cm ² at 77 K.

3. From an intimate mixture of 6,50g SrCO ₃ , 3,60g CaCO ₃ , 4,66g Bi ₂ O ₃ and 4,77g CuO a powder of the composition Bi ₂ Cai, eSr ₂ , ₂ Cu ₃ O _y by slow Heat to 82O ⁰ C and 24h hold at this temperature. From this powder, a molded article is prepared, which is treated as in Example 1, with the Un.-difference that the duration of the temperature treatment under Mikrogravitationsbedingungen 24h and the temperature while 89O ⁰ C, then at 0.1 K / min to 82O ⁰ C and then cooled to room temperature at 20K / min. The obtained superconductor has a critical temperature of 105 K and a critical current density at 77 K of 5 × 10 ⁶ A / cm ² .

Claims (1)

A process for the production of polycrystalline oxide high-temperature superconducting materials, wherein a powdery precursor is produced and deformed by thermal or chemical means, then heated up to or just above the temperature of the partial, incongruent Schmälzens the starting materials in oxygen or in an oxygen-containing atmosphere, however without obtaining a homogeneous melt, kept at this temperature and then cooled to complete solidification, characterized in that the heating is carried out under microgravitational conditions and the subsequent process steps can be carried out under microgravitational conditions. Field of application of the invention