Ferroic nanoclusters in relaxors:: the effect of oxygen vacancies

Single crystals of PbSc0.5Ta0.5O3 with suppressed and enhanced oxygen deficiencies and different degrees of long-range B-site ordering were studied by Raman spectroscopy in order to clarify the significance of the different factors for the formation and growth of ferroic clusters in relaxors. It is shown that the presence of oxygen vacancies impacts more strongly on the incipient ferroic clustering than the degree of long-range B-site ordering. The oxygen deficiency hinders the formation of ferroelectric crystalline-type nanoregions, regardless of the presence/absence of long-range B '/B ''-ordered regions. The low degree of defects in the O system enhances the long-range ferroelectric ordering, even in entirely B-site-disordered materials.