The mechanism of the decrease of barriers for oxygen ionic conductivity   in nanocrystalline ceramics
  We calculated the influence of surface tension on the barriers of oxygen ionic conductivity in nanograin ceramics. Activation energy of oxygen ions diffusion via oxygen vacancies which were considered as the dilatational centers was calculated. This energy was shown to decrease with nanoparticle sizes decreasing. The distribution function of activation energy was derived on the basis of distribution of nanoparticle sizes. We obtained an analytical expressions of ionic conductivity dependence on the temperature and nanograin sizes. These formulas fitted pretty good the observed earlier behaviour of oxygen conductivity in nanograin ceramics of ZrO2:16% Y observed earlier. Therefore the consideration we carried out had shown that the surface tension in nanoparticles is physical mechanism responsible for the essential enhancement of the oxygen ionic conductivity observed in nanograin samples, the main contribution to the conductivity being related to the region in vicinity of the particle surface. 
M.D.Glinchuk, P.I.Bykov, B.Hilczer