Superconductivity and Lattice Instabilities.
Final rept. 1 Oct 71-30 Sep 76,
CALIFORNIA UNIV SAN DIEGO LA JOLLA INST FOR PURE AND APPLIED PHYSICAL SCIENCES
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During the past five years four distinct advances in the science of superconductivity have been made 1 many new superconductors were discovered, including lithium-titanate Tc 13.7K and numerous Chevrel phases Tc 15.2K lead-molybenum-sulfide. The latter are remarkable not only for their extra-ordinarily high critical fields, which are close to 700 kg in some cases, but also for the fact that really high critical temperatures have for the first time been discovered in non-cubic materials. 2 Overwhelming evidence for a connection between moderate-to-high-temperature superconductivity and low temperature structural instability was found. Work on both the occurrence and the pressure dependence of superconductivity and lattice instability in zirconium-vanadium, hafnium-vanadium, lanthanum-ruthenium, ruthenium-vanadium, copper-molybdenum-sulfide, copper-molybdenum-selenide, zinc-molybdenum-sulfide, gold-zinc, lanthanum-sulfide, and lanthanum-selenide shows that the connection between the two phenomena is very general. 3 An empirical correlation between the shape of electrical resistivity versus temperature curve of a given superconductor and its transition temperature was developed. Despite incomplete understanding of its nature, this correlation was found to be useful in predicting superconductivity in some cases. 4 The transition temperatures of magnesium and gold 5 x 10-4 and 2 x 10-4K, respectively were found by means of extrapolation.
- Metallurgy and Metallography