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.