Synthesis, Crystal Structure, and Electronic Properties of the Tetragonal (REIREII)3SbO3 Phases (REI = La, Ce; REII = Dy, Ho)

In our efforts to tune the charge transport properties of the recently discovered RE(3)SbO(3) phases (RE is a rare earth), we have prepared mixed (RE(I)RE(II))(3)SbO(3) phases (RE(I) = La, Ce; RE(II) = Dy, Ho) via high-temperature reactions at 1550 °C or greater. In contrast to monoclinic RE(3)SbO(3), the new phases adopt the P4(2)/mnm symmetry but have a structural framework similar to that of RE(3)SbO(3). The formation of the tetragonal (RE(I)RE(II))(3)SbO(3) phases is driven by the ordering of the large and small RE atoms on different atomic sites. The La(1.5)Dy(1.5)SbO(3), La(1.5)Ho(1.5)SbO(3), and Ce(1.5)Ho(1.5)SbO(3) samples were subjected to elemental microprobe analysis to verify their compositions and to electrical resistivity measurements to evaluate their thermoelectric potential. The electrical resistivity data indicate the presence of a band gap, which is supported by electronic structure calculations.