Quantitative analysis of ceria co-doped with samarium and gadolinium using laser-induced breakdown spectroscopy

Ceria doped with low-valence lanthanide cations has been introduced for use as an electrolyte in solid oxide fuel cells (SOFCs). Improving the performance of SOFCs using doped ceria requires an increase in ion mobility across the solid electrolyte. Recently, ceria doped with multiple low-valence lanthanide ions has been found to show better ion mobility than that of the singly doped one. In this work, the feasibility of laser-induced breakdown spectroscopy (LIBS) for stoichiometric analysis of doubly doped ceria, SmGd_0.1-Ce_0.9O_2-, was investigated. The three lanthanide elements pouring out plenty of emission lines made identifying the well-resolved single emission line of the dopants (Sm and Gd) rarely feasible. However, the spectral feature of the dopants could be extracted from the unresolved spectra successfully by partial least squares-regression (PLS-R). The PLS-R model performance calibrating the LIBS spectra to the concentration of Sm or Gd was dependent on the contribution of the matrix element (Ce) to the latent variable chosen for modeling. The residual feature of Ce in the latent variable could be reduced further by smoothing LIBS spectra using a moving average. The best model showed dependable detection limit (0.83 mol% of Sm) and accuracy (0.24 mol% of Sm) performances. Spectral denoising by moving average and PLS-R modeling based on LIBS spectra can be used as a rapid and reliable methodology for the multiply doped ceria and assist the manufacturing and recycling processes of SOFCs.