Beneficial influence of iodine substitution on the thermoelectric properties of Mo3Sb7

Mo3Sb7 has been known as a p-type metal with commonly poor thermoelectric properties. However, Mo3Sb7 can be a high-efficiency thermoelectric material, owing to its capability of a metal–semiconductor transition, which can be realized by adding two valence electrons through elemental substitutions. Among the Mo3Sb7-based compounds, Mo3Sb5.4Te1.6 shows the highest figure of merit, zT, but additional valence electrons are needed for further improvement of the figure of merit. Here, we try to enhance the figure of merit of Mo3Sb7 by iodine-doping and by synthesizing and characterizing Mo3Sb7Ix with x = 0, 0.50, 0.75, 1.00, 1.25, and 1.50, where antimony (valence electrons = 5) is replaced by iodine (valence electrons = 7). We confirmed that the solubility limit for iodine in Mo3Sb7Ix was 1.25 < x < 1.50, and the figure of merit was enhanced by approximately 65% in maximum in x = 1.25.Mo3Sb7 has been known as a p-type metal with commonly poor thermoelectric properties. However, Mo3Sb7 can be a high-efficiency thermoelectric material, owing to its capability of a metal–semiconductor transition, which can be realized by adding two valence electrons through elemental substitutions. Among the Mo3Sb7-based compounds, Mo3Sb5.4Te1.6 shows the highest figure of merit, zT, but additional valence electrons are needed for further improvement of the figure of merit. Here, we try to enhance the figure of merit of Mo3Sb7 by iodine-doping and by synthesizing and characterizing Mo3Sb7Ix with x = 0, 0.50, 0.75, 1.00, 1.25, and 1.50, where antimony (valence electrons = 5) is replaced by iodine (valence electrons = 7). We confirmed that the solubility limit for iodine in Mo3Sb7Ix was 1.25 < x < 1.50, and the figure of merit was enhanced by approximately 65% in maximum in x = 1.25.