Charge distribution model in cubic perovskite-type compounds

R. E. ALONSO; A. LÓPEZ GARCÍA

Leipzig, Alemania

Congreso; XV International Symposium on Nuclear Quadrupole Interaction; 1999

A non-zero electric field gradient tensor, detected by probes that occupy sites with cubic pointgroup symmetry, was observed in many ABO3 perovskite-type compounds. This breakdown oflocal cubic symmetry is commonly associated with the presence of oxygen vacancies around theprobe. This effect in BaTixHf1􀀀xO3 with x = 0.7, 0.5, 0.3, 0.1, 0.05 and 0.01 is studied in thiswork. The cell parameters were obtained at laboratory temperature using XRD spectroscopy. Thehyperfine parameters were measured at a181Ta probe in the B site using Perturbed Angular Correlations(PAC) spectroscopy as a function of both temperature and composition. As a common trend,a static asymmetric and distributed quadrupolar interaction, strongly dependent on compositionhas been observed. The results, together with those corresponding to 1 > x  0.75, are analyzedusing the point-charge model in terms of polarized oxygen vacancies, different covalence of theTi-O and Hf-O bonds with computational simulation for the lattice positions of cations and oxygenvacancies.