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Superconductivity in LaSn(3), and LaTl(3)

IP.com Disclosure Number: IPCOM000094368D
Original Publication Date: 1966-Oct-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gambino, RJ: AUTHOR [+2]

Abstract

Lanthanum metal is a superconductor of very limited usefulness. This is because it has a relatively low critical temperature of 5 to 6 degrees K, corrodes very rapidly in air and occurs in two crystallographic modifications. The latter are difficult to obtain separately and have different superconductive properties. The latter characteristics prevent lanthanum from having a sharp transition to the superconductive state, an essential property of a switching device material.

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Superconductivity in LaSn(3), and LaTl(3)

Lanthanum metal is a superconductor of very limited usefulness. This is because it has a relatively low critical temperature of 5 to 6 degrees K, corrodes very rapidly in air and occurs in two crystallographic modifications. The latter are difficult to obtain separately and have different superconductive properties. The latter characteristics prevent lanthanum from having a sharp transition to the superconductive state, an essential property of a switching device material.

Most of the undesirable properties of La are eliminated when it is reacted with some of the elements from periodic groups IIIa and IVa to form intermetallic compounds. These compounds have the general formula LaX3 where X is Sn, Pb, or ;TI and have the cubic Cu3Au structure. The lattice constants a and superconductive transition temperatures Tc of these compounds are as follows: LaSn(3) 4.782 angstroms 6.35 degrees K LaPb(3) 4.903 angstroms 3.65 degrees K LaTl(3) 4.806 angstroms 1.6 degrees K. The compounds have much sharper transitions than elemental lanthanum and are considerably more corrosion resistant.

They are readily prepared by reacting stoichiometric amounts of the constituent elements in a capped tantalum crucible at about 1200 degrees C. The reaction is very exothermic, however. Thus the preparation of large quantities of material, 100 gm or more, is best carried out by slowly adding solid La to molten Sn, Pb or Tl and simultaneously increasi...