Synthesis and Thermoelectric Properties of Cs 2 Bi 7.33 Se 12 , A 2 Bi 8 Se 13 (A = Rb, Cs), Ba 4-x Bi 6+2/3x Se 13 , and Ba 3±x Pb 3±x Bi 6 Se 15

We are continuing our synthetic investigations in the ternary A/Bi/Se systems and also expanded our interests into the quaternary A/M/Bi/Se (A = Rb, Cs, Sr and Ba; M = lanthanide or Pb) systems. We have synthesized several new ternary and quaternary bismuth selenides with band gaps <0.6eV such as Cs 2 Bi 7.33 Se 12 , A 2 Bi 8 Se 13 (A = Rb, Cs), Ba 4-x Bi 6+2/3x Se 13 , and Ba 3±x Pb 3±x Bi 6 Se 15 . The synthesis, crystal structures and charge transports properties of these new compounds are presented.