CS272082B1 - Method of superconductive material treatment - Google Patents

Abstract

a method for treating a superconducting material based on copper / barium oxides and / or stronda and oxide of at least one element of lanthanum, carem / praseodymium / neodymium / samarium, europium, gadolinium; terbiem, dysproslsm, holmlem, thullsm, yttsrbiam, 'yttriem and akandle. The method of saving in the fact that it is superconducting grinding the material; ee 1 to 80 wt. of silver powder or silver compounds; which gets warmed up decompose, e.g. the mixture is heated at 850 ° C up to 1000 ° C.

Description

The invention relates to a process for the treatment of a superconducting material based on oxides of modi, barium and / or strontium and an oxide of at least one element from the group consisting of lanthanum, care, praseodymium; neodymium, samarium, europium, gadolinium / terbium, dysprosium; holmium; ytterbiem / yttriem a scandiem

Oxide-based materials Copper, barium and / or strontium and oxides of at least one element from the group consisting of lanthanum, cerium; prameodymium / neodymium, samarium, europisa, gadolinium, terbium, dysprosium, holmium, ytterbium, yttrium and scandium. Ba-Cu-O / which can be maintained in a superconducting state even at the temperature of liquid nitrogen. The superconducting state of these materials also shows a strong Meissner effect, manifested, among other things, by the repulsion of the magnet from the superconductor. He also uses the Meissner effect ee as evidence for the existence of a superconducting state of the samples. Said Materials are usually prepared in a manner based on ceramic technology from the starting powder compounds. In the case of YBagCu ^ O? they are oxides of YgOg, and CuO. The pure oxide powders were ground in the appropriate cation ratio and the resulting mixture was calcined at a temperature of about 900 ° C in air or in a stream of oxygen for several hours. Cold sintering is followed by annealing in an oxygen stream at 900 to 1000 ° C again for several hours. This is followed by cooling at a rate of about 200 ° C / hour. Further modifications of the process, e.g. the addition of additives of other elements to the above-mentioned superconducting material, do not bring significant advantages or improvements in the properties of the Material. A common feature of existing production methods is that zetiM do not allow the production of superconducting materials suitable for use in technical practice. The above-described method of production without the addition of additives is used for the production of laboratory and demonstration samples / for known technical applications of superconductors, however, this method is not suitable. In practice, low stability of superconducting and mechanical properties, low resistance to damage and some other parameters are insufficient for technical superconducting devices. Previously known modifications of said production method, in which additives of other elements are used / have led to an improvement of e.g. mechanical resistance to damage; at the same time, however, there was an undesirable decrease in the critical temperature and the Meisjner effect; or? the structure of the superconducting phase is disrupted / thus losing the main advantage of high-temperature superconductors.

This disadvantage is largely eliminated by a process for the treatment of a superconducting material based on oxides of copper, barium and / or etronium and an oxide of at least one element from the group consisting of lanthanum, cerium; praseodymium / neodymium, samarium / auropia, gadolinium, terbium, dysprosium, holnium; ytterbium / yttrium and scandium according to the invention. The object of the invention is to grind the incorporated superconducting material into a powder, to which powder is added powdered silver or a silver compound which decomposes on heating, and preferably silver oxide, in an amount of 1 to 80% by weight / premixed and the mixture obtained is after compression it is gradually heated to a temperature of 850 to 1000 ° C / left at this temperature for 10 minutes to 15 hours; after which it is allowed to cool,

The method of processing the superconducting material according to the invention has a number of advantages. In particular, it enables the production of superconducting materials with higher utility properties. The materials produced have high values of critical temperatures and show the Meissner effect similarly to pure materials without additives; while at the same time having improved resistance to damage and wear, as well as time stability of superconducting properties. The result is a significant reduction in scrap and facilitated machining. These advantages are a significant benefit for the production of technical superconductors. Despite these advantages, the technical difficulty of production does not increase compared to existing methods, and in most cases known prior art production equipment can be used.

The process according to the invention is explained in more detail in the following examples.

CS 272 082 Bl 2

Example 1

Superconducting ceramic material YBa ₂ Cu ₃ 0 ₇ , which is an orthorhombic modification; was crushed and ground to a mean grain size below 10 .mu.m and mixed thoroughly with the added Ag ₂ O. After thermal decomposition of the silver oxide Ag ₂ O and leakage of oxygen, 50% by weight of Ag was found in the remaining material. The resulting powder was compressed into tablets with a diameter of 16 mm and a height of 2 mm. The tablets were heated in a stream of oxygen to 920 ° C, where they were left for 1 hour, after which they were slowly cooled in an oven still in a flowing oxygen atmosphere. The sintered tablets were subjected to X-ray diffraction analysis. This showed that the resulting material contained a superconducting orthorhombic phase YBa ₂ Cu ₃ 0 ₇ without a trace of a superconducting tetragonal phase, and further that it contained unreacted silver. The samples were superconducting at the boiling point of liquid nitrogen, i.e. at 77 K, and showed a Meiesner effect, which was manifested by the floating of a permanent magnet SmCO _g measuring 3 x 3 x 3 mm in the air above the tablet.

Example 2

In the same manner as in Example 1, tablets of the same dimensions were prepared with an Ag content of 1 and 5% by weight and heated to a temperature of 920 ° C, where they were kept for 15 hours. The tablets again showed a Meiesner effect at 77 K. · It was again detected by X-ray diffraction analysis; that the material.contains a superconducting orthorhombic phase Y.Ba ₂ Cu ₃ 0 ₇ without a trace of tetragonal phase ·

Example 3

In the same manner and in the same dimensions as in Example 1, a sample with a content of 30% by weight was produced. After heating, it was kept at a temperature of 1000 ° C for 10 minutes in flowing oxygen. Another sample of the same dimensions; but with a content of 80% by weight. The Ag was heated in flowing oxygen to 890 ° C and maintained at this temperature for 1 hour. Both samples again showed the Meiesner effect after cooling. Similarly, other samples of superconducting material were made with admixtures of 1 to 80% by weight, silver.

The processing method according to the invention can be carried out on conventional equipment; known from powder 'metallurgy. Due to the brittleness of the superconducting material, grinding into a powder is relatively easy and is preferably carried out after coarse grinding, for example in a ball or friction mill. The pressing after mixing of the mixture is generally carried out cold in the usual pressing tools. Different pressing pressures can be used, with values of 0.5 GPs being sufficient for satisfactory results. The heating and heat treatment ee is carried out, for example, in electric resistance furnaces / preferably in an atmosphere of flowing oxygen and with slow cooling, for example at a rate of 100 ΐς / hour.

The process according to the invention can be used in the production of superconducting materials.

Claims (1)

Process for the treatment of a superconducting material based on oxides of copper, barium and / or strontium and an oxide of at least one element from the group consisting of lanthanam, cerium, praseodymium, neodymium, samarium, europium, gadolinium / terbium, dysprosium, holmium, erbium thulium, yttsrbium; yttrium and scandium, characterized in that the sintered superconducting material is ground to a powder, silver powder or a silver compound is added to this powder, which decomposes on heating; preferably silver oxide, in an amount of 1-80% by weight, blended and the resulting mixture was gradually heated after compression to a temperature of 850 to 1 OOO ^e C, at this temperature for 10 minutes to 15 hours; after which it is allowed to cool.