Synthesis and Characterization of High-Entropy-Alloy-Type Layered Telluride M Bi 2 Te 4 ( M = Ag, In, Sn, Pb, Bi).

Recently, high-entropy alloys (HEAs) and HEA-type compounds have been extensively studied in the fields of material science and engineering. In this article, we report on the synthesis of a layered system M Bi 2 Te 4 where the M site possesses low-, middle-, and high-entropy states. The samples with M = Pb, Ag 1/3 Pb 1/3 Bi 1/3 , and Ag 1/5 In 1/5 Sn 1/5 Pb 1/5 Bi 1/5 were newly synthesized and the crystal structure was examined by synchrotron X-ray diffraction and Rietveld refinement. We found that the M -Te2 distance was systematically compressed with decreasing lattice constants, where the configurational entropy of mixing at the M site is also systematically increased. The details of structural refinements and the electrical transport property are presented.