Chemistry and Electrocrystallization of Organic Metals and Superconductors

Abstract

Considerable variation in the conditions of electrochemical crystal growth of TMTSF₂X (i.e., constant current versus constant potential, ambient versus inert atmosphere, etc.) and in the purity of the constituents (donor, electrolyte, solvent) does not significantly affect the unusual low-temperature properties of this class of materials. Our results suggest that the electrocrystallization procedure may be self-purifying by selecting for conducting crystal phases with constituents having specific oxidation potentials and solubility properties. However, doping solutions with structurally and chemically similar constituents (i.e., TMTTF, and IO⁻ ₄ in CIO⁻ ₄) leads to their incorporation in the crystal structure where they have a profound effect. Several mole percent of these dopants suppress superconductivity in the PF⁻ ₆ and CIO⁻ ₄ salts, and increase and broaden the metal-insulator phase transition.