Modulation and Enhancement of Red Luminescence in Ca2GdSbO6: Eu3+ Phosphor by Co-Doping with Bi3.

The double perovskite structure of Ca₂GdSbO₆ as a fluorescent phosphor matrix material possesses a stable structure, making it an excellent candidate for a matrix material. In this study, single-doped Ca₂GdSbO₆: Eu³⁺ fluorescent phosphors and Bi³⁺ sensitized Ca₂GdSbO₆: Eu³⁺, Bi³⁺ fluorescent phosphor materials were synthesized using the high-temperature solid-state method. The luminescence of this phosphor is based on the ⁵D₀→⁴F₂ transition emission of Eu³⁺ ions, which occurs at 612 nm. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectra, high-temperature fluorescence spectra, and fluorescence decay lifetimes to study the phase structure, optical properties, crystal structure, and chemical purity of the samples. The performance of the single-doped phosphor was significantly improved by the addition of Bi³⁺ sensitizer. The luminescence intensity increased by nearly 100% compared to Ca₂GdSbO₆: Eu³⁺ phosphor, with a quantum efficiency increase of 124%. The thermal quenching activation energy was found to be 0.299 eV, and the luminescence intensity remained at 70.3% of room temperature at 453 K. These results indicate that the co-doping of Bi³⁺ has a modulation and enhancement effect on the luminescence of Ca₂GdSbO₆: Eu³⁺ red phosphor, showing great potential for application in near-ultraviolet-excited white LED devices.