<p>A new series of red phosphors, Ca_2-xSrWO₆: Eu³⁺(x = 0.1, 0.2, 0.3, 0.4, 0.5), was synthesized using a high-temperature solid-state technique. The phase composition, crystal structure, luminescent properties, and thermal stability of the synthesized phosphors were examined through X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, high-temperature fluorescence spectroscopy, and fluorescence decay lifetime assessments. The findings demonstrate that Ca_2-xSrWO₆: xEu³⁺ phosphors may be efficiently stimulated by 395&#xa0;nm near-ultraviolet light, resulting in pronounced red light emission at 614&#xa0;nm. The light intensity predominantly arises from the ⁵D₀ → ⁷F₂ transition of Eu³⁺ at 614&#xa0;nm. The luminescence intensity of Ca_2-xSrWO₆: xEu³⁺ phosphors increases initially followed by a decrease with increasing Eu³⁺ doping concentration. Concentration quenching occurs at a doping concentration of x = 0.3, and this phenomenon is attributed to electric dipole–electric dipole (d–d) interactions in accordance with Dexter’s theory. Moreover, the fluorescence lifetime decreases progressively with increasing Eu³⁺ doping concentration. The CIE color coordinates and thermal stability of the Ca_1.7SrWO₆: 0.3Eu³⁺ sample were examined. The color coordinates (0.6585, 0.3410) roughly align with the typical red light coordinates (0.670, 0.330). The color purity reached 96.5%, with the luminous intensity at 423&#xa0;K nearly 75% of that at ambient temperature. The results suggest that Ca_2-xSrWO₆: xEu³⁺ is a promising candidate for a new red phosphor in white light-emitting diode (WLED) applications.</p>