Surface and grain boundary energies of tin dioxide at low and high temperatures and effects on densification behavior

This work presents experimental data on the surface and grain boundary energies of tin dioxide nanoparticles at room temperature and high temperature conditions (quenched from 1300 degrees C), and a discussion of impacts on the fundamental understanding of the nondensification mechanism of SnO2 during sintering. The results were obtained using a combination of water adsorption microcalorimetry, high-temperature oxide melt drop solution calorimetry, and scanning electron transmission microscopy. At room temperature, the average surface and grain boundary energies of anhydrous SnO2 were 1.20 +/- 0.02 and 0.71 +/- 0.08 J m(-2), respectively. At high temperature, SnO2 showed a surface energy of 0.94 +/- 0.03 J m(-2). This remarkable decrease was attributed to the lower oxygen pressure and was associated with a decrease in contact angle during sintering. This observation indicates a moderate but significant thermodynamic reason behind nondensification behavior of SnO2 in addition to common kinetic descriptions: high sintering temperatures and atmospheres cause smaller dihedral angles that decrease sintering stresses.