In situ XRD studies of stability of crystalline structure of Ce-Zr-Sc mixed oxides

SALETA, MARTÍN EDUARDO; LAMAS, DIEGO GERMÁN; TOSCANI, LUCIA M.; LARRONDO, SUSANA

Campinas

Conferencia; 28th Annual Users? Meeting LNLS; 2018

CNPEM

Solid Oxide Fuel Cells stand as a promising technology for efficient and sustainable energy production. Anode material is subjected to high temperatures during the construction process and the operation of the SOFC1. Therefore, it is important to study the impact of temperature on material stability. The aim of this work is to study the effect of temperature in composition homogeneity, secondary phase segregation and crystallite size in CeO2-ZrO2-Sc2O3 mixed oxides. The addition of Sc2O3 to CeO2-ZrO2 system is expected to improve ionic conductivity through aliovalent doping of the mixed oxide lattice and, as a consequence,improve overall anode performance.Samples were synthesized using two different routes, namely glycine/nitrate combustion route (GC) and citrate complexation route (CIT), preparing the following nominal compositions: Ce0,9ScxZr0,1-xOδ, with 0 ≤ x ≤ 0.1. The crystal structure of the samples prepared was studied by means of in situ X-ray powder diffraction (XPD) experiments performed at the D10B-XPD beamline of the LNLS. Samples were studied using a high intensity and low resolution configuration without analyzer crystal and a Mythen 1K detector. Samples were heated from ambient temperature to 1000°C in air flux to study structural evolution. In addition they were subjected to CH4/O2 atmospheres to study structure stability in complete methane combustion reaction conditions. In situ XPD experiments allowed us to confirm the successful incorporation of Sc2O3 into the CeO2-ZrO2 mixed oxide prepared both by citrate and glycine/nitrate routes and fired at 500°C. The samples exhibited a cubic fluorite type structure characteristic of CeO2. Crystallite size growth kinetics was similar for all prepared samples, however, ternary samples exhibited lower values of crystallite size in the whole temperature range, reaching values of ca. 60 nm at 1000 °C. Catalytic experiments indicated structural stability in reaction conditions with no formation of graphitic carbon doing complete combustion experiments.