<p>A series of europium Eu³⁺-doped orange-red emitting phosphors were synthesized through a high-temperature solidphase reaction using NaSr₄(BO₃)₃ as the host in an atmosphere of air. The effects of calcination temperature and the contents of boric acid and Eu³⁺ on the photoluminescent properties of the as-prepared phosphors were investigated. In particular, the addition of boric acid in excess of the stoichiometric ratio could significantly improve the singlephase purity of the host. Meanwhile, the synthesis times for the phosphors were also reduced. The crystal phases and fluorescent properties of NaSr_4–x(BO₃)₃:xEu³⁺ were characterized using X-ray powder diffraction analysis and a fluorescence spectrophotometer, respectively. The luminescent intensity of the phosphor was highest at the calcination temperature of 880°C for 3 h, which was the optimum condition for forming single-phase NaSr₄(BO₃)₃ hosts. All prepared NaSr₄(BO₃)₃ phosphors belonged to the cubic crystal system. The maximum excitation wavelength was 392 nm. The main emission peaks were observed at 591 nm (orange light) and 615 nm (red light), which corresponded to the ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions of Eu³⁺, respectively. Furthermore, NaSr_3.92(BO₃)₃:0.04Eu³⁺ reached the maximum intensity of the main emission peaks, and the red-emitting performance was outstanding. The ratio (R/O) of the intensities of the emission peaks of red and orange lights could be affected by changes in the contents of Eu³⁺, so as to enrich and simplify the strategies for improving the red-emitting light purity. This provides a basis for the development of high-brightness and high-color-purity red-emitting phosphors for LED chips excited by nearultraviolet light.</p>