  We present a detailed analysis of the temperature dependence of the thermal
conductivity of a ferroelectric PbTiO3 thin film deposited in a
composition-spread geometry enabling a continuous range of compositions from
~25% titanium-deficient to ~20% titanium-rich to be studied. By fitting the
experimental results to the Debye model we deconvolve and quantify the two main
phonon scattering sources in the system: ferroelectric domain walls (DWs) and
point defects. Our results prove that ferroelectric DWs are the main agent
limiting the thermal conductivity in this system, not only in the
stoichiometric region of the thin film ([Pb]/[Ti]~1), but also when the
concentration of cation point defects is significant (up to ~15%). Hence, DWs
in ferroelectric materials are a source of phonon scattering at least as
effective as point defects. Our results demonstrate the viability and
effectiveness of using reconfigurable DWs to control the thermal conductivity
in solid-state devices.
