The influence of dopants on the surface enthalpy of Yttrium aluminum garnet (YAG)

Abstract

Surface enthalpy is an important parameter to predict the phase stability of crystalline materials at the nanoscale, having parametric influence in processes such as coarsening and single crystal nucleation and growth. Yttrium aluminum garnet (Y3Al5O12, YAG) is a base material for solid state laser, with limited thermodynamic information on interfacial energies available. In the present study, we experimentally determined the surface enthalpy of YAG by using microcalorimetry. Nanoparticles were used to maximize the respective measurable heat effect exploiting their intrinsically high surface areas. We further tracked the effect of La or Mg as dopants on the surface enthalpy of YAG. The results indicate that there is a slight reduction in the surface enthalpy of YAG nanoparticles after doping with 2 mol%-La or Mg. The anhydrous surface enthalpy of undoped YAG was measured as 1.28 ± 0.11 J/m2 and was reduced to 0.98 ± 0.09 and 1.11 + 0.07 J/m2 for 2 mol%-La, and Mg doped YAG nanoparticles, respectively, confirming anhydrous surface energies of YAG can be modified by dopants. The effect of water adsorption on the energies, however, show that the differences between doped and undoped YAG surface energies become negligible at relative pressures as low as 20%, challenging surface energy control as a viable process optimization parameter in the presence of humidity.