Synthesis, characterization and transport properties of Pr0.50Ln0.50BaCo2O5+δ (Ln: Pr, Nd, Sm, Eu, Gd, Tb and Dy)

In this work, we present the new compounds Pr 0.50 Ln 0.50 BaCo 2 O 5+ δ (Ln: Pr, Nd, Sm, Eu, Gd, Tb and Dy) that we have synthesized as pure phase polycrystalline materials by the Pechini method. Doping the A site with a second heavier lanthanide promotes smaller oxygen stoichiometry, providing an alternative way to modify the oxygen content of these Pr-cobalt oxides by means of changing the PrLn ratio. According to powder X-Ray diffraction the compounds display an average tetragonal structure. The presence of smaller Ln ions together with a smaller amount of oxygen gives rise to higher Seebeck coefficients, specially from PrEu to PrDy, and to a substantial increase of the resistivity below 200 K. As a result the highest power factor is displayed by the Pr 0.50 Eu 0.50 BaCo 2 O 5.69 sample at ∼125 K, PF max ∼0.154 μW K −2 cm −1 , value that is two orders of magnitude higher than that shown by the starting PrBaCo 2 O 5.76 sample at the same temperature.