Anomalous X-Ray Diffraction Study of Pr-substituted BaCeO3-d

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

Workshop; Sao Paulo School of Advanced Science on Recent Developments in Synchrotron Radiation; 2015

The effect of Pr doping on thecrystal structure and site occupancy was studied for the nominally synthesizedBaCe1-xPrxO3-d (x = 0, 0.2, 0.4, 0.6 and 0.8)perovskites using anomalous X-ray powder diffraction data and Rietveld analysis.Crystal structure parameters were accurately determined by using 10000 eVphotons, and the Pr occupancy was refined using data collected  with 5962 eV photons, close to Pr LIIIabsorption edge. BaCe1-xPrxO3-d crystallizesin the Pnma (N° 62) Space Group forall x values [1].  Pr cations are mainlylocated 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 contentincreases [2]. The Pr doping introduces electronic defects (Pr+3/Pr+4)and oxygen vacancies needed for H2O incorporation and H-ionicconductivity. The decrease of the orthorhombic distortion would produceopposite effects on the electronic and ionic mobility [3]. The electronicmobility should increase due to an improvement in the overlap of the(Ce/Pr)4f-O2p  orbital, while the protonmobility should decrease as a consequence of a larger hopping distance [4].