Crystal growth and thermoelectric properties of CaMn sub(0.98)Nb sub(0.02)O sub(3- delta )

Thermoelectric CaMn sub(0.98)Nb sub(0.02)O sub(3- delta ) single crystals were grown from sintered polycrystalline material using the traveling-solvent floating zone (TSFZ) method. The floating-zone furnace was operated at overpressure using an Ar/O sub(2) mixture to prevent evaporation during the growth process. Six twin-domain variants were detected with single-crystal X-ray diffraction (XRD) and confirmed by electron diffraction (ED) and high-resolution transmission electron microscopy (HRTEM). The Seebeck coefficient (S) of the single-crystalline material indicates n-type semiconducting behavior. Within 10 K < T< 125 K a negative peak in S is observed, known to be characteristic of antiferromagnetic ordering. The ferromagnetic long-range ordering, expected on the basis of double exchange between Mn super(4+) and doped Mn super(3+) species, thus appears to remain suppressed in the single-crystalline material.