The effect of the application of a dc current on the annealing of point defects in Ni3Ti was investigated by positron annihilation spectroscopy. An increased defect annealing rate was observed under the influence of the current and was attributed to a 24% decrease in the activation energy of mobility. The results are interpreted in terms of the electron wind effect and the complex nature of diffusion in ordered intermetallic phases. They provide direct evidence for an increase in defect mobility in ordered intermetallics under the influence of a current. (C) 2004 American Institute of Physics.

Fully stabilized nanometric zirconia samples with varying degrees of porosity and grain sizes were analyzed using the coincidence Doppler broadening mode of the positron annihilation spectroscopy (PAS). A decrease in the low-momentum fraction was observed and coincided with a decrease in porosity. In addition to pores, it is proposed that defects in the negatively charged grain-boundary space region act as positron trapping centers; their effectiveness decreases with an increase in grain size. It is shown that PAS is sensitive to small grain-size differences within the nanometric regime in these oxide materials. (c) 2006 American Institute of Physics.