NUKLEONIKA 2010, 55(1):85-89

 


POSITRON-ANNIHILATION AND PHOTOLUMINESCENCE STUDIES
OF NANOSTRUCTURED ZrO2



Janusz D. Fidelus1, Andrzej Karbowski2, Sebastiano Mariazzi3, Roberto S. Brusa3, Grzegorz Karwasz2

1 Institute of High Pressures of the Polish Academy of Sciences,
29/37 Sokołowska Str., 01-142 Warsaw, Poland

2 Institute of Physics, Nicolaus Copernicus University (UMK),
5 Grudziądzka Str., 87-100 Toruń, Poland

3 Dipartimento di Fisica, Universita di Trento, 14 Sommarive Str., I-38100 Povo (Trento), Italy


In the present work, photoluminescence and Doppler broadening depth-resolved positron annihilation spectroscopy was performed on pure zirconia nanopowders. Zirconia nanopowders were grown by a hydrothermal microwave-driven process followed by annealing in oxygen atmosphere. Photoluminescence under 274 nm wavelength excitation from a 150 W high-pressure Xe exhibits similar spectra, in the region from 320 to 820 nm, although its intensity depends on the annealing. Positron annihilation Doppler-broadening spectra show low values of the normalized S-parameter, varying little with the depth, from 0.495 on the surface to 0.47–0.49 in bulk. Both high the annealing temperature and oxygen concentrations, lead to low bulk S-values. The ortho-positronium (o-Ps) fraction is about 10–11% for all samples on the surface, whereas it is reduced to 7–8% in the bulk for samples annealed at 700°C and 5–6% for samples annealed at 800°C. Both photoluminescence (PL) and positron studies show the presence of defects in all samples. The o-Ps signal suggests a high porosity of samples, particularly at a depth down to 10 nm.


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