Enhancing thermoelectric properties in strontium barium niobate high-entropy ceramics through configurational entropy modulation

One of the key strategies for enhancing the thermoelectric figure of merit (ZT) is the simultaneous optimization of electron and phonon transport. In this work, (Sr 0.25 Ba 0.25 La 0.25 Pb 0.25 ) 1-x Nb 2 O 6-δ (0 ≤ x ≤ 0.15) ceramics were synthesized via the solid-state reaction method. By introducing a series of A-site defects into the high-entropy system, configurational entropy was modulated to optimize thermoelectric performance. As the value of x increased, both electrical resistivity and thermal conductivity exhibited significant reductions. Due to the synergistic effect of relatively high power factor (PF) and low thermal conductivity (κ), the sample with x = 0.1 achieved a peak ZT value of 0.19 at 1073 K, representing a 137.5 % enhancement over the stoichiometric ceramic sample. This research demonstrates that in the distorted tetragonal tungsten bronze structure, enhanced crystal symmetry facilitates electron delocalization, thereby improving electrical transport properties. Additionally, defects, including edge dislocations confirmed by scanning transmission electron microscopy analysis, increase the likelihood of random scattering events, leading to a reduction in lattice thermal conductivity. This study demonstrates that in (Sr 0.25 Ba 0.25 La 0.25 Pb 0.25 )Nb 2 O 6−δ high-entropy ceramics, the synergistic modulation of A-site defect concentration and configurational entropy effectively optimizes electron and phonon transport properties , thereby achieving a peak ZT value of 0.19.