Thermal Properties of Yttrium Aluminum Garnett from Molecular Dynamics Simulations

Abstract

Yttrium Aluminum Garnet (YAG,Y_(3)Al_(5)O_(12)) and its varieties have applications in thermographic phosphors, lasing mediums, and thermal barriers. In this work, thermal properties of crystalline YAG where aluminum atoms are substituted with gallium atoms (Y_(3)(Al_(1-x)Ga_(x))(5)O(12))) are explored with molecular dynamics simulations. For YAG at 300K, the simulations gave values close to experimental values for constant-pressure specific heat, melting temperature, and thermal expansion. For various values of x, the simulations predicted no change in thermal expansion, and a decrease in specific heat with increasing x. The melting temperature was difficult to determine however. Non-equilibrium simulations predicted bulk thermal conductivity approaching experimental bulk values. Furthermore, conductivity for x=0 was higher than that of x=1, which was in turn higher than that of x=0.5 for all system sizes.