Établissement des diagrammes de phases isothermes pour deux systèmes ternaires combinant Le graphite et deux métaux insérés

Laboratoire de chimie du solide minéral (URA CNRS 158), université de Nancy I, BP 239, 54506 Vandœuvre-Iès-Nancy Cedex, France.

Résumé

Nous avons établi les diagrammes de phases isothermes graphite- potassium-mercure à 270 °C et graphite-potassium-thallium à 340 °C. Les alliages lamellaires qu'on y observe sont des binaires graphite-potassium à feuillets insérés monocouches et des ternaires à feuillets insérés multicouches (tricouches dans Le cas des amalgames, et pentacouches dans celui des alliages de thallium).

Abstract

Two isothermal phase diagrams have been established, for the graphite- potassium-mercury system at 270 °C on the one hand, and for the graphite- potassium-thallium system at 340 °C on the other hand. Tlie various observed solid phases are lamellar intercalation compounds, which appear in fact as foliated alloys. Three binary phases only have been retained, corresponding to stages 1, 2 and 3 (KC₈, KC₂₄ and KC₃₆), because the poorer compounds do not appear finally during the experiments. Otherwise, in every system, two well characterized temary phases appear, respectively of stages 1 and 2. It is a matter of KH_gC₄ and KH_gC₈ temaries on the one hand, and KTI_1.5C₄ and KTI_1.5C₈ on the other hand. While the binary phases present mono-layered intercalated sheets, these temaries contain multi-layered thick sheets : K-Hg-K three-layers in one case and K-TI-TI-TI-K five-layers in the other. These various temary lamellar alloys are electric conductors and all become superconductors for critical temperatures comprised between 1.5 and 2.8 K.