Work

Unravelling the Effects of Calcium Substitution in BaGd 2 CoO 5 Haldane Gap 1D Material and Its Thermoelectric Performance

Year: 2020

Type: article

Abstract: Ecobenign and high-temperature-stable oxides are considered a promising alternative to traditional Bi 2 Te 3 -, Bi 2 Se 3 -, and PbTe-based thermoelectric materials. The quest for high-performing thermoelectric oxides is still open and, among other challenges, includes the screening of various materials systems for potentially promising electrical and thermal transport properties. In this work, a new family of acceptor-substituted Haldane gap 1D BaGd 2 CoO 5 dense ceramic materials was characterized in this respect. The substitution of this material with calcium results in a general improvement of the electrical performance, contributed by an interplay between the charge carrier concentration and their mobility. Nevertheless, a relatively low electrical conductivity was measured, reaching ∼5 S/cm at 1175 K, resulting in a maximum power factor of ∼25 μW/(K × m 2 ) at 1173 K for BaGd 1.80 Ca 0.20 CoO 5 . On the other hand, the unique anisotropic 1D structure of the prepared materials promotes efficient phonon scattering, leading to low thermal conductivities, rarely observed in oxide electroceramics. While the BaGd 2– x Ca x CoO 5 materials show attractive Seebeck coefficient values in the range 210–440 μV/K, the resulting dimensionless figure of merit is still relatively low, reaching ∼0.02 at 1173 K. The substituted BaGd 2– x Ca x CoO 5 ceramics show comparable thermoelectric performance in both inert and air atmospheres. These features highlight the potential relevance of this structure type for thermoelectric applications, with future emphasis placed on methods to improve conductivity.

Source: The Journal of Physical Chemistry C

DOI: 10.1021/acs.jpcc.0c03149