Enhanced luminescent performance of high-entropy perovskite phosphor (Ca_0.2Sr_0.2Ba_0.2La_0.2Na_0.2)_1-xEu_xTiO₃

High-entropy oxides have demonstrated exceptional performance in structural materials, but their potential as functional hosts for luminescent ions remains largely unexplored. Here, we designed and synthesized an A-site high-entropy perovskite phosphor, (Ca_0.2Sr_0.2Ba_0.2La_0.2Na_0.2)_(1-x)Eu_xTiO₃ (x = 0–0.10 mol). First-principles calculations reveal that high-entropy engineering modulates the electronic structure of the matrix, leading to band gap alteration and the regulation of intermediate energy levels, which may promote more efficient energy transfer. The high-entropy system induces severe lattice distortion and increased microstrain, resulting in reduced local symmetry around Eu³⁺ ions. In addition, XPS and EPR results confirm a suppressed concentration of oxygen vacancies in the high-entropy system. Compared with the Sr_0.92Eu_0.08TiO₃, (Ca_0.2Sr_0.2Ba_0.2La_0.2Na_0.2)_0.92Eu_0.08TiO₃ phosphor exhibits a fivefold enhancement in luminescence intensity, an extended fluorescence lifetime of 605.75 μs, and a higher quantum yield of 18.61%. The improved performance is attributed to the synergistic increase in the radiative transition rate and the suppression of non-radiative relaxation pathways. Furthermore, the (Ca_0.2Sr_0.2Ba_0.2La_0.2Na_0.2)_0.92Eu_0.08TiO₃ phosphor exhibits enhanced thermal stability with a higher activation energy (0.365 eV) and improved color purity (98.5%), indicating a more saturated red emission. This work demonstrates that high-entropy design enables simultaneous regulation of local coordination, electronic structure, and defect chemistry, offering an effective strategy for developing red phosphors.