Anomalous X-ray diffraction study of Pr-substituted BaCeO3-d

JUAN F. BASBUS ; ALBERTO CANEIRO; LEOPOLDO SUESCUN; DIEGO G. LAMAS; LILIANA V. MOGNI

ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Año: 2015 vol. 71 p. 455 - 462

0108-7681

The effect of Pr doping on the crystal structure and site occupancy was studied for the nominally synthesized BaCe1 xPrxO3 (x = 0, 0.2, 0.4, 0.6 and 0.8) perovskites using anomalous X-ray powder diffraction (AXRD) data and Rietveld analysis. Crystal structure parameters were accurately determined using 10000 eV photons, and the Pr occupancy was refined using data collected with 5962 eV photons, close to the Pr LIII absorption edge. BaCe1-xPrxO3 crystallizes in the Pnma (No. 62) space group for all x values. Pr cations are mainly located at the Ce sites (perovskites B site), but a small fraction of them increasingly substitute some of the Ba ions at the A site as Pr content increases. The Pr doping introduces electronic defects (Pr+3/Pr+4) and oxygen vacancies needed for H2O incorporation and H-ionic conductivity. A decrease in the orthorhombic distortion would produce the opposite effects on the electronic and ionic mobility. The electronic mobility should increase due to an improvement in the overlap of the (Ce/Pr)4f?O2p orbital, while the proton mobility should decrease as a consequence of a larger hopping distance.