Thermoelectric properties and thermal stability of layered chalcogenides, TlScQ2, Q = Se, Te

Facile synthesis and magnetic and electrical properties of layered chalcogenides K2CoCu3Q4 (Q for S and Se)

Layered transition-metal chalcogenides have attracted great interest due to their unique electronic and optical properties. Here, we represent two layered quaternary chalcogenides K2CoCu3S4 and K2CoCu3Se4 prepared by a convenient hydrothermal route. From powder XRD and TEM analyses, K2CoCu3Q4 possesses a tetragonal ThCr2Si2-type structure with a random arrangement of Co and Cu atoms. The phase purity of the samples was confirmed by ICP, SEM, and EDS analyses, and the oxidation states of Co and Cu atoms were determined to be +3 and +1 by XPS spectra. Both samples show a weak ferromagnetic behavior at low temperature induced by spin-canted antiferromagnetic ordering. The temperature dependent resistivity, ρ(T), reveals a metallic nature for stoichiometric K2CoCu3S4. The semiconducting behavior of K2CoCu3Se4 could be explained better by variable range hopping (VRH) rather than adiabatic small polaron hopping (SPH). This new series of layered chalcogenides may offer a promising candidate for potential electronic applications.