Influence of sintering temperature and Li+/Mg2+ doping on the thermoelectric properties of Bi2−2x Li x Mg x Sr2Co2O y

ABSTRACT Bi2−2x Li x Mg x Sr2Co2O y (x = 0.05, 0.10 and 0.15) samples are prepared by a solid-state reaction at various temperatures (1033–1133 K). All X-ray diffraction peaks can be indexed as the monoclinic Bi2Sr2Co2O y phase. The structural and thermoelectric properties of Bi2−2x Li x Mg x Sr2Co2O y samples are systematically investigated, depending on the sintering temperature and the Li+/Mg2+ concentration. A higher sintering temperature increases the hole concentration and hole mobility, whereas a higher Li+/Mg2+ concentration increases the hole concentration and decreases the hole mobility. As the Li+/Mg2+ concentration increases, the power factor of the samples sintered at 1033 K decreases, whereas that of the samples sintered at 1083 and 1133 K increases. Of the prepared samples, Bi1.70Li0.15Mg0.15Sr2Co2O y sintered at 1133 K shows the largest power factor (0.25 × 10−4 W m−1 K−2) at 973 K. This power factor is 2.5 times greater than that of Bi1.70Li0.15Mg0.15Sr2Co2O y sintered at 1033 K (0.10 × 10−4 W m−1 K−2) at 973 K.