Influence of the oxygen content and the preparation method on the power factor of PrBaCo2O5+δ samples (0.54 ≤ δ ≤ 0.84)

In this work, we focus on the influence of the oxygen content and the preparation method on the power factor of different PrBaCo2O5+δ samples (0.54 ≤ δ ≤ 0.84). The samples have been initially synthesized by the Pechini method. Their oxygen content has been subsequently modified by annealing under argon/oxygen flow or by electrochemical oxidation/reduction. The oxygen stoichiometry has a high impact on the electrical conductivity and Seebeck coefficient of the resulting materials. Moreover, by adequately reducing their oxygen content while increasing their intergrain conductivity (by increasing the particle size and degree of sintering) the power factor of these samples can be drastically improved. The best result is shown by the PrBaCo2O5.54 sample, that was annealed at high temperature under argon flow, whose power factor is as high as 6.5 μW/K2 cm−1 at ∼135 K, more than two orders of magnitude higher than that shown by the initial PrBaCo2O5.76 reference sample.

Research highlights
► Synthesis of single-phase materials with oxygen content between 5.54 and 5.84.
► Great influence of the oxygen content on the magnetic and transport properties.
► PrBaCo2O5.54 sample shows the highest value of the power factor.