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

J.F. BASBUS; A. CANEIRO; L. SUESCUN; D. LAMAS; L.V. MOGNI

ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2015 vol. 71 p. 455 - 462

0108-7681

The effect of Pr doping on the crystal structure and site occupancy was studiedfor 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 andRietveld analysis. Crystal structure parameters were accurately determinedusing 10 000 eV photons, and the Pr occupancy was refined using data collectedwith 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 aremainly located at the Ce sites (perovskites B site), but a small fraction of themincreasingly 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 vacanciesneeded for H2O incorporation and H-ionic conductivity. A decrease in theorthorhombic distortion would produce the opposite effects on the electronicand ionic mobility. The electronic mobility should increase due to animprovement in the overlap of the (Ce/Pr)4f?O2p orbital, while the protonmobility should decrease as a consequence of a larger hopping distance.