Superconductivity in the W-Tc and W 2C-Tc systems

Abstract

A series of compositions were prepared in the W-Tc and W 2C-Tc systems and the lattice parameters and superconducting transition temperatures, T k, determined. Three phases occur in the W-Tc system: an A2-tye (bcc) solid solution extending from 0 to 50 at.% Tc with the T k increasing to 8.2 K; a sigma phase region from 60 to 75 at.% Tc where the T k increases from 7.1 to 9.0 K; and an A3-type (hcp) solid solution over the range of 82 to 100 at.% Tc in which the T k decreases from the maximum value of 10.3 K at the phase boundary to the 7.9 K value of Tc. The hexagonal W 2C forms a continuous solid solution with technetium and is superconducting over the entire range. As the technetium content is increased, the T k of the W 2C decreases from 3.3 K to a minimum value of 2.5 K at 50 at.% Tc and then rises smoothly to 7.9 K as the Tc concentration is increased from 50 to 100 at%. Similar measurements were also made on the W 2CRe system.