Substitutions in the Homologous Family CsPb_mBi_3Te_(5+m) and Preliminary Thermoelectric Results

摘要

We report analogs of the homologous family CsPb_mBi_3Te_(5+m), namely Cs_(0.74)K_(0.76)Bi_(3.5)Te_6 (1), CsNa_(0.98)Bi_(4.01)Te_7 (2), Cs_(0.69)Ca_(0.65)Bi_(3.34)Te_6 (3), Rb_(0.82)Pb_(0.82)Bi_(3.18)Te_6 (4), Rb_(0.19)K_(1.31)Bi_(3.50)Te_6 (5), RbSnBi_3Te_6 (6), Rb_(0.94)Ca_(0.94)Bi_(3.06)Te_6 (7) and RbYbBi_3Te_6 (8). They all crystallize in the orthorhombic space group Cmcm and are isostructural to CsPbBi_3Te_6 the first member of the family except for CsNa_(0.98)Bi_(4.01)Te_7 which is isostructural to CsPb_2Bi_3Te_7, the second member of the family. The R_1 factor was 0.0455 for (1), 0.0491 for (2), 0.0367 for (3), 0.0287 for (4), 0.0458 for (5), 0.0498 or (6), 0.0560 for (7) and 0.0356 for (8). Preliminary thermoelectric measurements on Cs_(0.76)K_(0.74)Bi_(3.5)Te_6 show electrical conductivity values in the range of 600-1000 S/cm. The thermopower shows n-type charge transport with room temperature values of ～ -35 μV/K. By comparison, the electrical conductivity at room temperature of Rb_(0.82)Pb_(0.82)Bi_(3.18)Te_6 was ～1400 S/cm, while the thermopower was ～ -20 μV/K.