Agency of Industrial Science and Technology

Agency of Industrial Science and Technology Ministry of International

Kunihiko Oka

Hiromi Unoki

Zhigang Zou

Hiroshi Akoh

Toshimitsu Ito

PrBa.sub.2 Cu.sub.3 O.sub.Y exhibiting superconductivity is provided by a method including the steps of preparing a solvent consisting of a mixture of praseodymium oxide, at least one of barium oxide and barium carbonate, and copper oxide at a mixing ratio of between 1:3:5 and 1:8:20, disposing the solvent between a feed rod of PrBa.sub.2 Cu.sub.3 O.sub.7 formed to a high density and a seed crystal, heating the solvent to a temperature of 880.degree.-980.degree. C. in an atmosphere of an inert gas of at least one of argon and nitrogen mixed with 0.01-2% oxygen to form a floating solvent zone, moving the floating solvent zone toward the feed rod at 0.1-1.0 mm/hr under a temperature gradient at the solid-liquid interface of 25.degree.-35.degree. C./mm to precipitate single crystal on the seed crystal, and heat-treating the single crystal obtained in an atmosphere containing not less than 15% oxygen. Another aspect of the invention provides a superconducting device including the superconducting PrBa.sub.2 Cu.sub.3 O.sub.Y single crystal material in combination with at least one non-superconducting PrBa.sub.2 Cu.sub.3 O.sub.Y crystal material.

Method of producing superconducting PrBa.sub.2 Cu.sub.3 O.sub.y single

Lanthanum cuprate, La.sub.2 CuO.sub.4, is a superconductive oxide. In order to prepare a single crystal of lanthanum cuprate, the phase diagram of La.sub.2 O.sub.3 -CuO system is determined utilizing their differential thermal analysis and X-ray diffractometry. Cu oxide and at least one of lanthanum oxide and lanthanum carbonate are mixed in the molar ratio of 71.1-92.9:28.9-7.1. The resulting mixture is heated to be molten. While slowly cooling the melt, nuclei of La.sub.2 CuO.sub.4 precipitate from the melt, growing to single crystals in the melt. As a result, large scale single crystals are prepared.

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Tsukuba, Japan

Kunihiko Oka