Despite the great benefits that the sintering process provides for the final properties of a ceramic material, facilitating many of its applications, it is undeniable that the energy consumed in conventional sintering methods is enormous since the process requires high temperature. A strategy to avoid the use of high temperatures and long sintering times is to use electric field-assisted sintering techniques. Among these techniques, much of the scientific attention focused on Spark Plasma Sintering (SPS). The SPS provides fast heating rate and short sintering processing time, and represents thus a relevant process to prepare nanostructured ceramics. As a consequence of microstructural modification, changes in the final properties of the material can occur.
In this context, a new family of Pr, Sm and Zr mixed oxides were synthesized by the solvothermal method and sintered as pellets by SPS at 1350 °C for 5 minutes. Then the structural and electrical properties, as well as the reoxidation kinetics, were evaluated by different characterization techniques. The results show the obtention of materials with a single-phase pyrochlore structure for all the synthesized compositions. There is no change in the crystalline phase of the materials after the SPS sintering process. Moreover, ceramics were achieved with a relative density higher than 95%, a value considered high in comparison to the conventional sintering method (Tsint: 1400 °C), for which the obtained relative density usually reaches only 70%. SEM micrographs of the cross-section of the SPS ceramics show a microstructure made of nanograins. The electrical properties and oxidation kinetics were studied by Impedance Spectroscopy (IS). When following the reoxidation process by changing the atmosphere from argon to air, it was possible to evidence an increase in the conductivity of the material, a behavior that is all the more pronounced for the compositions with higher Pr concentration, due to the oxidation of part of Pr(III) to Pr(IV). In an oxidizing atmosphere, the samples become more conductive and exhibit lower activation energy. The conductivity values obtained are comparable to well-studied components of SOFCs, like YSZ, GDC and LSGM, for example. Thus, due to their thermal stability, good densification, and good conductivity, these pyrochlore materials are promising for the application as fuel cell components for clean energy production.