Non-equilibrium acoustic phonons in nanocrystalline ceramics based on C-modification of Y2O3 sesquioxide

The transport processes in highly transparent nanocrystalline laser-host ceramics based on C-modification of Y2O3 sesquioxide were investigated by the heat-pulse technique. The propagation kinetics of acoustic phonons was studied in the range of liquid helium temperature (1.7-3.8 K). A structural model for the grain boundary layers is suggested and their thickness is estimated.