Thermal conductivity and heat capacity of the relaxor ferroelectric [PbMg1/3Nb2/3O3]1-x[PbTiO3]x

The evolution of thermal conductivity and heat capacity for the series of [PbMg1/3Nb2/3O3](1-x)[PbTiO3](x) (PMN-PTx) single crystals with 0 <= x <= 1 are reported. PMN shows typical glasslike behavior in both measurements, which is attributed to the presence of polar nanoregions. With PT doping up to the region of morphotropic phase boundary (MPB), the plateau in thermal conductivity is progressively suppressed. This is reminiscent of partially crystallized glasses and suggests enhanced thermal boundary resistance from ferroelectric domains. The linear temperature contribution and large C-p/T-3 peak in heat capacity remain nearly constant for PT doping up to the MPB but are rapidly suppressed for larger x. These results demonstrate that thermal properties are intimately coupled to the local structures in relaxor ferroelectric systems.