Thermodynamic analysis of phase stability of nanocrystalline titania

TLDR

Surface free energy and stress govern the size‑dependent thermodynamic stability of nanocrystalline titania. Thermodynamic analysis was performed to compare the phase stability of nanocrystalline anatase and rutile. Anatase is more stable than rutile below 14 nm, and the calculated phase boundary matches experimental observations of rutile formation during coarsening.

Abstract

The phase stability of nanocrystalline anatase and rutile was analyzed thermodynamically. According to the present analysis, anatase becomes more stable than rutile when the particle size decreases belowca. 14 nm. The calculated phase boundary between nanocrystalline anatase and rutile coincides with the experimental data for appearance of rutile during coarsening of nanocrystalline anatase. Both surface free energy and surface stress play important roles in the thermodynamic phase stability, which is a function of particle size.