ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Polymerization of carbon diselenide, CSe2, at 5 kbar and ∼100 °C has been reported to give a metallic (CSe2)n ladder polymer that superconducts near 6 K at 220 kbar pressure. Using a variety of techniques we find that the material synthesized (showing essentially the same x-ray diffraction pattern as previously published) is not (CSe2)n but instead consists of a mixture of free, trigonal Se and an amorphous C–Se polymeric composition consistent with the formula (CSe0.5)n. Interestingly, possibly as a consequence of staged reactions during synthesis, the Se phase consists of a mixture of large, aggregated crystallites (∼600 A(ring) in diameter) melting at ∼220 °C and nonaggregated small crystallites (∼150–250 A(ring) in diameter) showing a broad melting transition with an endothermic maximum at ∼180 °C. Percolation of the C–Se polymeric composition probably provides the high observed electrical conductivity [σ(300 K)≈10–20 S cm−1 and σ(300 K)/σ (8 K)≈2.5] in the presently available samples. The previously reported high pressure superconductivity is probably associated with the free Se phase in the samples, since selenium is a known superconductor in the 6 K and 220 kbar range.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.450870
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