Dopagem da composição LaNi0,5Cr0,5O3-δ com Ca, para determinação de condutividade eletrônica e estabilização de fase para utilização em eletrodo de célula a combustível.

Abstract

Ceramics of the LaNi₀.₅Cr₀.₅O₃ (LNC55) composition were synthesized and doped with different calcium concentrations to investigate the effects of Ca incorporation on structural stability, microstructure, and electronic conductivity, aiming at their application as electrode materials in Solid Oxide Fuel Cells (SOFCs). The oxide-mixing route was adopted as an environmentally sustainable alternative to the Pechini method while preserving perovskite phase formation. The samples were sintered between 1200 and 1500 °C and characterized by X-ray diffraction, Rietveld refinement, Archimedes density measurements, scanning electron microscopy, impedance spectroscopy, and Raman spectroscopy. XRD analyses confirmed that all compositions predominantly maintained an orthorhombic perovskite structure (PDF 75-441) throughout the sintering range, with slight lattice parameter variations associated with La³⁺ substitution by Ca²⁺ and consistent with solid-solution formation. Density measurements showed that calcium doping enhanced densification, especially for compositions LCNC8255 and LCNC7355, which reached porosity below 5% at 1400 °C. Microstructural analysis revealed improved densification and good grain connectivity while preserving functional porosity for electrode operation. Impedance spectroscopy demonstrated a significant enhancement in electronic conductivity, particularly for composition LCNC9155, which exhibited the highest conductivity value (0.42 S/cm). Raman spectroscopy confirmed the preservation of the perovskite structure and revealed vibrational variations related to dopant concentration and sintering temperature. Overall, the results indicate that calcium doping optimizes microstructure and electronic performance, making the studied compositions promising candidates for SOFC electrode applications.