Exchange of metal atoms in solid mixed-valence Tl I3TlIIICl6. Conductivity and positron annihilation investigations

Abstract

Physical techniques have been applied to derive information on isotopic exchange in mixed-valence Tl₄Cl₆. Using the positron as a probe, it has been found that cation-vacancy formation is relatively easy, with an activation energy of 0.35 eV. Conductivity measurements have shown that Tl₄Cl₆ is a good ionic conductor in the temperature range where exchange proceeds (470–550 K) with an activation energy for conduction of 0.69 eV. Comparing these energies with the activation energy derived in a previous chemical study shows that the exchange process is triggered by the presence of anion vacancies.