HIGH-PRESSURE SYNTHESIS OF YTTRIUM-THORIUM SESQUICARBIDE - A NEW HIGH-TEMPERATURE SUPERCONDUCTOR

A new, high-temperature superconductor, yttrium-thorium sesquicarbide, has been prepared by high-pressure-high-temperature techniques. The phase, crystallizing in the b.c.c., Pu2C3-type structure, exists over a wide ternary field. Lattice parameters are dependent on the Y Th metal and C Mt carbon-total metal atomic ratios. The material is superconducting with a variable transition temperature, having a maximum at 17.0 °K. High-temperature ambient-pressure annealing results in the destruction of both the b.c.c. structure and the high-temperature superconductivity. A ternary b.c.t. phase, previously unreported, has been identified in a number of arc-melt preparations. This phase exists over a wide ternary field and is not superconducting down to 4 °K. Elements other than thorium have been incorporated in yttrium sesquicarbide with resultant enhancement of the superconducting temperature. © 1969.