HPHT synthesis of highly doped InxCo4Sb12 – Experimental and theoretical study

Abstract Indium-filled skutterudite In x Co 4 Sb 12 with high filling fraction x (above the solubility limit) was synthesized using HPHT synthesis method. Obtained samples were characterized by means of XRD with Rietveld structural refinement and XPS methods, confirming the introduction of indium filler into structural voids in much higher concentration than solubility limit in ambient conditions. The electrical and thermal properties measurements carried out for temperature range of 4–300 K showed increased carrier concentration and simultaneously decreased Seebeck coefficient and thermal conductivity. Additionally, DFT calculations for In x Co 4 Sb 12 ( x  = 0, 0.125, 0.25, …, 1) were carried out employing PBE and modified Becke-Johnson (mBJ) exchange-correlation potentials. Analysis of calculated band structures indicated that increase of In content in CoSb 3 voids results in significant decrease of band gap size due to down-energy shift of conduction band at H point of first Brillouin zone. Net charges of topological atoms calculated within QTAiM model were found to be consistent with tendencies observed in XPS measurements. The obtained results show that using HPHT synthesis method allowed obtaining materials with filler element concentration being much higher than solubility limit in ambient conditions and therefore modifying the structure of skutterudite materials (and thus its thermoelectric properties) to a larger extent.