Ultralow Lattice Thermal Conductivity of Cubic CuFeS₂ Induced by Atomic Disorder

Lattice thermal conductivity is of great importance to design high-performance thermoelectric (TE) materials. In chalcopyrite (CuFeS2) with an ordered tetragonal structure, which is an environmentally friendly TE material, the lattice thermal conductivity is as high as 9.0 W m–1 K–1 at 300 K. Here, we demonstrate that the lattice thermal conductivity of CuFeS2 is significantly reduced from 9.0 to 1.5 W m–1 K–1 by the phase regulation at ambient temperature, in which the tetragonal structure is transformed to the cubic structure. It is verified that the dramatically reduced lattice thermal conductivity essentially originates from the enlargement of the Grüneisen parameter caused by disordered atom rearrangement and lattice distortion. By further alloying with Al, the lattice thermal conductivity of the cubic CuFeS2 polycrystalline compound approaches a predicted glass limit value of 0.45 W m–1 K–1 at 723 K. The results highlight the potential of realizing low lattice thermal conductivity by atomic disorder in TE compounds with intrinsically high lattice thermal conductivity.