Abstract: A method and an apparatus for cooling an superconducting material below the boiling point of liquid nitrogen by using liquid nitrogen as coolant. The cooling method of the invention can be used in two different modes, one under reduced pressure and the other under the atmospheric pressure. The former comprises a coil container which is in fact a vacuum vessel and the temperature of which is lowered by to the triple point of nitrogen by means of a vacuum pump. The latter comprises a coil container containing therein a cooling section of a freezer and the temperature of the coil container is lowered to the melting point of nitrogen by the freezer.

Abstract: The present invention relates to an oxide superconductor comprising a composite oxide of RE , Ba and Cu, wherein the superconductor comprises a micro structure comprised of a monocrystalline REBa.sub.2 Cu.sub.3 O.sub.7-x phase (123 phase) and a RE.sub.2 BaCuO.sub.5 phase (211 phase) finely dispersed therein, the 123 phase being formed in a plurality of domains respectively for individual RE compositions and in the order of the 123 phase forming temperatures in respective layers.

Abstract: The present invention is characterized in that oxides of Y, Ba and Cu having a superconductive substance-forming composition are melted, the melt is rapidly cooled and solidified, the obtained sheet is heated at a temperature of 1000.degree. to 1350.degree. C. to produce a partially melted state thereof, and the sheet is gradually cooled at a rate lower than 200.degree. C./hr, whereby a texture in which grains of the RE.sub.2 BaCuO.sub.5 phase having a diameter smaller than 20 .mu.m are dispersed in the REBa.sub.2 Cu.sub.3 O.sub.7-y phase is obtained.

Abstract: Disclosed is an oxide superconductor comprising an oxide of RE, Ba and Cu, which consists of a superconductor having a texture wherein the crystal directions of the 123 phase in the matrix are uniform, large angle grain boundaries having an directional difference larger than 20.degree. are not present and the 211 phase is finely dispersed, or an aggregate thereof, wherein the superconductor is formed into a plate or wire and the c-axis of the crystal of the formed body is uniform within .+-.30.degree. to the normal of the plate face of the formed body or in the range of from 60.degree. to 120.degree. to said normal. Also disclosed is a process for the preparation of an oxide superconductor as set forth above, which comprises inserting a formed body as mentioned above to a heating furnace and moving a region of a temperature at which grains are formed in the 123 phase of the matrix of the formed body, i.e., through a region having a temperature of from 1050.degree. to 910.degree. C.

Abstract: In a refrigerating apparatus comprising a rotary compressor, a pressure-controlled valve is inserted in a path between a condenser and an evaporator and a reverse flow check valve is inserted between the evaporator and a suction line connected to the input port of the rotary compressor, thereby to eliminate undesirable heat load caused by undesirable flow-in of the refrigerant gas into the evaporator after the rotary compressor stops.