Synthesis, Crystal and Electronic Structure, and Thermal Conductivity Investigation of the Hollandite-like Cs_xCr₅Te₈ Phases (0.73 < x < 1)

This article presents a comprehensive study on the synthesis and structural and thermal conductivity properties of cesium-inserted chromium tellurides of formula Cs_xCr₅Te₈. Single crystals of three different compositions (x = 0.73, 0.91, and 0.97) were successfully synthesized and suggested the existence of a solid solution in the range 0.73 < x < 1. Through a detailed single-crystal characterization, the complete structure of these compounds is determined, revealing a distinct B-type hollandite-like structural form derived from the hollandite structure, in contrast to the more commonly observed A-type pseudo-hollandite in AM₅X₈-type chalcogenides (A = cation, M = transition metal, and X = chalcogen). Periodic density functional theory calculations predict the Cs_0.73Cr₅Te₈ composition as the most stable, with a metallic conductive behavior. The thermal conductivity of bulk Cs_xCr₅Te₈ samples is measured to be 1.4 W m^-1 K^-1 at 300 K and increases with temperature up to 2 W m^-1 K^-1 at 673 K.