Doping control and thermoelectric properties in R1-xAxZnSbO (R = La, Ce; A = Ca, Sr)

As the two-dimensional analogues of a conventional thermoelectric semiconductor ZnSb, we investigated the thermoelectric properties of layer-structured R(1-x)A(x)ZnSbO (R = La, Ce; A = Ca, Sr) using the polycrystalline samples with compaction density around 55%, combining with the electronic band-structure calculation. We found that the carrier concentration of RZnSbO can be controlled by substituting A(2+) for R3+ in the charge-reservoir layers without lowering the carrier mobility. The hole-doped materials exhibited relatively low thermal conductivity and a moderately high Seebeck coefficient, whose temperature and doping dependence were well reproduced by the calculation. ZT values were found to increase without showing saturation up to 390 K, and even higher values would be expected along the conducting ZnSb layers for a single crystal. These results indicate the potential of the hole-doped RZnSbO as a good thermoelectric material.