Thermal signatures of nanoscale inhomogeneities and ferroelectric order in [PbZn1/3Nb2/3O3](1-x)[PbTiO3](x)

We present the results of thermal conductivity (kappa) and heat-capacity (C-p) measurements for the series of [PbZn1/3Nb2/3O3](1-x)[PbTiO3](x) (PZN-xPT) single crystals with 0 < x < 1. Compared to the prototypical glasslike kappa found in PbMg1/3Nb2/3O3 (PMN), PZN shows a suppressed plateau in the temperature dependence of kappa. This feature of PZN resembles those of PT-doped PMN and is consistent with the coexistence of polar nanoregions (PNRs) and mesoscopic ferroelectric domains in this relaxor compound. For PT-doped PZN, the systematic behavior of kappa and C-p suggests that PNRs persist up to slightly beyond the morphotropic phase boundary at x approximate to 0.1. The high-temperature C-p data on PZN show a broad ferroelectric anomaly, which gradually transforms to a sharp ferroelectric transition with increasing PT content.