n型CaTiO₃における結合極性の弱化と格子軟化による熱電性能の相乗的向上を目的とした欠陥工学

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 ZT 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.