Abstract
The hyperfine quadrupole interaction at probes in sites with cubic point
group symmetry was measured in many perovskite-type compounds. This
interaction is commonly associated to the presence of oxygen vacancies
close to probes. The effect of this point defect on Ta-181 probe in BaTi x Hf1-xO3 for x = 0.70, 0.50, 0.30, 0.10, 0.05, and 0.01, is studied.
The lattice constant of these oxides at room temperature were measured
using XRD technique. The quadrupole parameters corresponding to
probe-defect interaction were obtained by means of Perturbed Angular
Correlation (PAC) spectroscopy as functions of both, composition and
temperature. A static, asymmetric and distributed quadrupole interaction
was fitted to all PAC data. This interaction was observed to be strongly
composition dependent. These results and those corresponding to
compositions 0.75 less than or equal to x < 1 were compared to the ones
obtained using the point charge method for the calculation of the
electric field gradient. The proposed model took into account polarized
oxygen vacancies, different covalence of Ti-O and Hf-O bonds and using
computational simulation for cations and oxygen vacancies lattice
positions.
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