Thermoelectric Properties of Doped (ZnO)mIn₂O₃

The thermoelectric properties of layer-structured homologous compounds of (ZnO) m In 2 O 3 ( m is an integer) were investigated in terms of the detailed dependence of the molar ratio of ZnO to In 2 O 3 , n (=ZnO/In 2 O 3 ), and of doping, such as with Ba 2+ , Ca 2+ , Sr 2+ , and Sn 4+ , for an In site. Except for the Ba and Sr dopings, all sintered specimens with n ≥3 were found to be in the phases of (ZnO) m In 2 O 3 . The highest power factor apparently existed around n =3 while the thermal conductivity was minimum at the range from n =3.5 to 5. The Ca doping effectively reduced the thermal conductivity, resulting in a dimensionless figure of merit of 0.23 (at 1053 K) for n =3.5, which was relatively high among n-type oxides.