Thermodynamic stability of SnO₂ nanoparticles: The role of interface energies and dopants

The stability of nanoparticles is strongly dependent on the thermodynamics of interfaces. Providing reliable data on surface and grain boundary energies is therefore of key importance for predicting and improving nanostability. In this work, we used a combination of high-temperature oxide melt drop solution calorimetry and water adsorption microcalorimetry to demonstrate the effect of a dopant (manganese) on both surface and grain boundary energies of SnO₂, and discussed the impacts on the average particle size at a given temperature. The results show a significant decrease in the grain boundary energy with increasing manganese content and a concomitant moderate decrease in the surface energy, consistently with segregation enthalpy values acquired from an analytical fitting model. The results explain the measured increase in stability with increasing dopant content (smaller sizes) and suggest the grain boundary energy has a much more important role in defining particle stability than previously supposed.