The mechanism of the decrease of barriers for oxygen ionic conductivity in nanocrystalline ceramics

TL;DR

This paper investigates how surface tension in nanocrystalline ceramics reduces activation energy barriers for oxygen ion diffusion, leading to enhanced ionic conductivity, with analytical models matching experimental observations.

Contribution

It provides an analytical framework linking nanoparticle size, surface tension, and ionic conductivity, explaining the observed increase in oxygen ion mobility in nanograin ceramics.

Findings

Activation energy decreases with smaller nanoparticle sizes.

Analytical expressions accurately fit experimental conductivity data.

Surface tension is identified as the key physical mechanism enhancing ionic conductivity.

Abstract

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.