Investigations of luminescence properties of cyan-blue phosphor Li₂Al₂B₂O₇:Eu²⁺

Rare-earth-activated alumino-borates have garnered significant interest due to the rigid framework, rich luminescence, and nonlinear optical capabilities. Eu²⁺-, and Eu²⁺/Mg²⁺-activated Li₂Al₂B₂O₇ were synthesized using the sol-gel method. Li₂Al₂B₂O₇ possesses a wide band gap (E_g = 4.77 eV) and exhibits an indirect transition. The investigation included analyses of phase purity, photoluminescent (PL) spectroscopy, thermal activation energy, luminescence quantum efficiency, and decay lifetimes of the Eu²⁺ activators. An intense cyan-blue luminescence band with a peak wavelength at 495 nm was detected. The Eu²⁺/Mg²⁺ co-doping in Li₂Al₂B₂O₇ not only significantly enhances luminescence efficiency but also improves thermal stability. This cyan-blue luminescent phosphor demonstrates excellent thermal stability, maintaining 85 % of its initial brightness at 150 °C. Li₂Al₂B₂O₇:Eu²⁺ phosphor exhibits scintillation luminescence with a fast decay lifetime under the excitation of X-ray irradiation at room temperature. With its outstanding luminescence efficiency and thermal stability, Li₂Al₂B₂O₇:Eu²⁺ is a promising candidate phosphor for lighting and scintillation applications.