Phonon scattering mechanisms dictating the thermal conductivity of lead zirconate titanate (PbZr1-xTixO3) thin films across the compositional phase diagram

This work represents a thorough investigation of the thermal conductivity (kappa) in both thin film and bulk PbZr1-xTixO3 (PZT) across the compositional phase diagram. Given the technological importance of PZT as a superb piezoelectric and ferroelectric material in devices and systems impacting a wide array of industries, this research serves to fill the gap in knowledge regarding the thermal properties. The thermal conductivities of both thin film and bulk PZT are found to vary by a considerable margin as a function of composition x. Additionally, we observe a discontinuity in j in the vicinity of the morphotropic phase boundary (MPB, x = 0.48) where there is a 20%-25% decrease in j in our thin film data, similar to that found in literature data for bulk PZT. The comparison between bulk and thin film materials highlights the sensitivity of j to size effects such as film thickness and grain size even in disordered alloy/solid-solution materials. A model for the thermal conductivity of PZT as a function of composition (kappa(x)) is presented, which enables the application of the virtual crystal approximation for alloy-type material systems with very different crystals structures, resulting in differing temperature trends for j. We show that in the case of crystalline solid-solutions where the thermal conductivity of one of the parent materials exhibits glasslike temperature trends the compositional dependence of thermal conductivity is relatively constant for most values of x. This is in stark contrast with the typical trends of thermal conductivity with x in alloys, where the thermal conductivity increases dramatically as the composition of the alloy or solid-solution approaches that of a pure parent materials (i.e., as x = 0 or 1). Published by AIP Publishing.