A new yellowish‐green‐emitting phosphor: Eu²⁺‐doped Ba₃YAl₂O7.5

A yellowish‐green emitting phosphor Ba 3 YAl 2 O 7.5 :Eu 2+ was synthesized by a solid‐state method. The crystal structure, luminescence, concentration quenching, fluorescence decay, and thermal quenching properties were systematically investigated. Under blue light (440 nm) excitation, Ba 3 YAl 2 O 7.5 :Eu 2+ phosphors exhibit a yellowish‐green emission peaking at 550 nm with a full width at half maximum ∼ 69 nm, and The Commission Internationale de l'Eclairage (CIE) coordinates of Ba 3 YAl 2 O 7.5 :Eu 2+ are (0.4064, 0.5811). Structural analysis and Van Uitert equation along with fluorescence lifetime analysis reveal that Eu 2+ ions occupy 6‐coordinated Y and 9‐coordinated Ba sites in Ba 3 YAl 2 O 7.5 , and therefore generate two emission sub‐bands at 582 and 548 nm. In addition, Ba 3 YAl 2 O 7.5 :Eu 2+ phosphor remaining 43% photoluminescence emission intensity at 125°C with an activation energy of 0.372 eV. Utilizing the title phosphor (Ba 3 YAl 2 O 7.5 :3%Eu 2+ ), commercial red (Ca,Sr)AlSiN 3 :Eu 2+ (CSAlSi:Eu 2+ ) phosphor, and InGaN‐based blue light emitting diode (LED) chip, a proof‐of‐concept warm white LEDs (WLEDs) with a color rendering index of 80.1, CIE chromaticity coordinates of (0.411, 0.381), luminous efficacy of ∼ 22.13 lm/W, and correlated color temperature of ∼ 3288 K is achieved. Thus, Eu 2+ activated Ba 3 YAl 2 O 7.5 phosphors have the potential application in WLEDs pumped by a blue LED chip for solid‐state lighting application.