Abstract
The effect of chromia (Cr2O3) additive on defects in yttria (Y2O3) stabilized zirconia (ZrO2) was examined in the present work. Two kinds of samples were investigated: (i) compacted nanopowders with grain size of 12-23 nm and (ii) sintered ceramics. Defect characterization was performed by high resolution positron lifetime spectroscopy. Because of nanocrystalline grain size positrons in compacted nanopowders probe almost exclusively grain boundaries. It was found that in compacted nanopowders positrons are trapped in vacancy-like misfit defect at grain boundaries and in larger defects situated at triple points. On the other hand, in ceramics positrons are annihilated predominantly in Zr-vacancies in grain interiors. Our results give a strong evidence for segregation of Cr cations at grain boundaries. Positron lifetime results for compacted nanopowders are strongly influenced by the Cr2O3 concentration, while results obtained in ceramics are very similar independently on the Cr2O3 content. Moreover, it was found that Cr2O3 additive completely suppresses the formation of positronium in open inter-granular volumes.
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