Propagation of nonequilibrium phonons in ferroelectric ceramics and singlecrystals

Phonon transport in ferroelectric ceramics and single crystals has been exp erimentally investigated. Our measurements indicate that, in the temperatur e range 1.7-3.8 K studied, the effective phonon diffusion coefficient behav es as D (eff)proportional to T-5 in ferroelectrics with a broadened phase t ransition. This experimental dependence is in accord with the presence of a plateau in the thermal conductivity of such materials. The scattering by d omain walls in BaTiO3 single crystals has been identified, and our results are in quantitative agreement with calculations. (C) 1999 American Institut e of Physics. [S1063-7761(99)01702-3].