Structure evolution and thermal conductivity of multi-component perovskite oxides regulated by synergistic dynamic–static high pressure and high-entropy strategies

In oxide thermoelectrics, controlling phonon transport is crucial for reducing lattice thermal conductivity.In this work, we report the synthesis of a series of high-entropy perovskite ceramics with the composition (Sr 0.6 La 0.2 Ca 0.1 Eu 0.1 )(Ti 0.6- x Nb 0.2 Hf 0.1 Zr x )O 3 , using a combined high-pressure high-temperature (HPHT) and high-energy ball milling (HEBM) process. This multistep route constructs a hierarchical phonon scattering network from the atomic to nanoscale. We find that the sample with Zr content x  = 0.09 exhibits the lowest lattice thermal conductivity of 0.89 W m −1  K −1 at 873 K, representing a substantial reduction compared to undoped SrTiO 3 . The suppression of thermal conductivity is attributed to synergistic phonon scattering mechanisms, including point-defect scattering from mass and bonding fluctuations, grain boundary scattering from nanoscale refinement, and enhanced Umklapp scattering due to lattice anharmonicity, as confirmed by TEM analysis and Grüneisen parameter calculations. The incorporation of high-entropy A- and B-site dopants induces local structural disorder and stress fields, further promoting phonon incoherence. This study demonstrates that coupling high-entropy chemical disorder with pressure-driven microstructure control enables effective decoupling of phonon transport pathways. The approach offers a promising strategy for designing next-generation oxide thermoelectric materials with intrinsically low lattice thermal conductivity and robust structural integrity.