Defect Engineering for Synergistically Enhanced Thermoelectric Performance in n-Type CaTiO ₃ via Weakened Bond Polarity and Lattice Softening

CaTiO₃-based compounds have emerged as promising thermoelectric materials due to their environmental benignity, thermal stability, and cost-effectiveness. However, the strong polar character of the metal-oxygen bonds imposes a fundamental limitation on the electrical conductivity, thereby restricting the overall thermoelectric performance. Herein, we demonstrate that defect engineering could induce synergistic effects, manifested in (i) a weakness of chemical bond polarity, which significantly enhances carrier mobility from ∼4.9 to ∼25.1 cm² V^-1 s^-1 at 600 K. (ii) the introduction of substantial lattice distortions and strain, effectively suppressing the lattice thermal conductivity. (iii) a softened crystal lattice to further suppress phonon propagation. Consequently, a peak <i>ZT</i> value of 0.35 is acquired for Ca_0.85Nd_0.15Ti_0.95Nb_0.05O₃ at 1073 K, approximately 337.5% higher than that of the pristine CaTiO₃ sample. Our investigation provides insights into how aliovalent doping can simultaneously modulate electrical and phonon transport properties, contributing a valuable design principle to the field of thermoelectrics.