Effective Thermal Conductivity of SrBi$_4$Ti$_4$O$_{15}$-La$_{0.7}$Sr$_{0.3}$MnO$_3$ Oxide composite: Role of Particle Size and Interface Thermal Resistance

TL;DR

This study investigates how particle size and interface thermal resistance influence the reduction of thermal conductivity in SrBi4Ti4O15-La0.7Sr0.3MnO3 oxide composites, with implications for thermoelectric energy harvesting.

Contribution

It introduces a novel analysis of interface thermal resistance effects and particle size on thermal conductivity in oxide composites using the Debye model and acoustic impedance mismatch.

Findings

Thermal conductivity decreases significantly when particle size is below the Kapitza radius.

Interface thermal resistance dominates thermal behavior for small particle sizes.

Composite thermal conductivity can be engineered by controlling particle size and interface properties.

Abstract

We present a novel approach to reduce the thermal conductivity ($\kappa$) in thermoelectric composite materials using acoustic impedance mismatch and the Debye model. Also, the correlation between interface thermal resistance (R$_{int}$) and the particle size of the dispersed phase on the k of the composite is discussed. In particular, the $\kappa$ of an oxide composite which consists of a natural superlattice Aurivillius phase (SrBi$_4$Ti$_4$O$_{15}$) as a matrix and perovskite (La$_{0.7}$Sr$_{0.3}$MnO$_3$) as a dispersed phase is investigated. A significant reduction in the $\kappa$ of composite, even lower than the $\kappa$ of the matrix when the particle size of La$_{0.7}$Sr$_{0.3}$MnO$_3$ is smaller than the Kapitza radius (a$_K$) is observed, depicting that R$_{int}$ dominates for particle size lower than a$_K$ due to increased surface to volume ratio. The obtained results have the potential to provide new directions for engineering composite thermoelectric systems with desired thermal conductivity and promising in the field of energy harvesting.