Order-Disorder Transition in AgCrSe2: a New Route to Efficient Thermoelectrics

The features of potentially efficient thermoelectric material, AgCrSe 2, exhibiting high Seebeck coefficient, relatively high electrical resistivity, but ultralow thermal conductivity comparable to that of a glass are presented. AgCrSe2 has electrical resistivity ranging in the tenths of milliω· cm. The layered compound AgCrSe2 is a known Ag-ion conductor whose structure can be described as CdI2-type layers of CrSe2- in which the Cr3+ cations are in a distorted octahedral coordination by Se2- anions. There are two different tetrahedral sites in the structure of AgCrSe2 situated between the CrSe2- sandwiches that form a slightly puckered honeycomb lattice. The disorder created by the mixed occupation of the cationic site by the calcium and the ytterbium deteriorates the thermal conduction that becomes temperature independent.