Red-emitting materials have significant applications in full-spectrum lighting， plant growth and medical health fields. Nevertheless， the development of thermally-stable broad-band red-emitting materials is still key issue. Due to the 6s² outer electron configuration of Bi³⁺ ions， the energy splitting can be controllably adjusted by the surrounding crystal field environment， further achieving the luminescence tuning over the visible and near-infrared region. Herein， we successfully achieve the doping of Bi³⁺ ions in LaSr₂SbO₆ double perovskite structure with broad-band orangish red emission. LaSr₂SbO₆：Bi³⁺ material exhibits broad excitation in the region of 300-450 nm， matching well with the commercial near-ultraviolet InGaN chip. Under 370 nm excitation， the optimal emission wavelength locates at 600 nm， with the full width at half maximum of 108 nm. The accurate structure analysis and theorical calculations confirm that Bi³⁺ ions preferentially occupy at La³⁺ site. Through adding H₃BO₃ as flux and designing heterovalent substitution strategy， the luminescence efficiency optimization， spectral tuning and thermal stability enhancement are further achieved. As a result， the luminescence efficiency can reach 46%， around 30 nm redshift can be adjusted. Meanwhile， LaSr₂SbO₆：Bi³⁺ material presents superior thermal stability. Even anti-thermal-quenching performance can be obtained in the region of 77-300 K， of which the luminescence intensity at 252 K can realize 141% of that at 77 K based on the addition of H₃BO₃ flux. Good thermal stability can be also achieved in the region of 298-523 K， the luminescence intensity at 423 K can keep 76% than that at room temperature. The above luminescence optimization can be attributed to the following reasons， first， the addition of H₃BO₃ flux reduces the generation of La₃SbO₇ impurities and increases the crystallizes of samples. Then， heterovalent substitution strategy can induce the localized structure modulation surrounding Bi³⁺ ions. The proposed luminescence optimization strategy can provide reference significance for the development and improvement of Bi-activated red-emitting materials.

Red-emitting materials;Bi³⁺ doped;double perovskite structure;Heterovalent substitution