Boosting Superior Dielectric Performance and Vicker Hardness in TiO ₂ ‐Based Materials by High‐Entropy Engineering

High‐entropy engineering has emerged as a transformative strategy to enhance the functional properties of ceramic materials. In this study, we synthesized and systematically evaluated high‐entropy TiO 2 ‐based ceramics, [Ta 0.5 (In 0.2 Tm 0.2 Gd 0.2 Ga 0.2 La 0.2 ) 0.5 ] x Ti 1‒ x O 2 ( x = 0.5%, 1%, 2%, 3%), incorporating multiple donor‒acceptor cation pairs to achieve synergistic improvements. The optimized composition exhibited an extraordinary dielectric constant of ∼2.7 × 10 4 , ultra‐low dielectric loss of 0.007 at 1 kHz, and exceptional thermal stability across a wide temperature range. These outstanding properties are attributed to the interplay of internal barrier layer capacitance and electron‐pinned defect dipole effects. Additionally, high‐entropy engineering introduced significant lattice distortions, resulting in a 109% increase in Vickers hardness compared to undoped TiO 2 . First‐principle calculations demonstrate that high‐entropy doping with trivalent–pentavalent ion pairs in rutile TiO 2 stabilizes multiple defect configurations. This work highlights the potential of high‐entropy engineering as a robust tool for advancing TiO 2 ‐based dielectric ceramics, while establishing a solid foundation for material innovations.