A bright orange-red emitting phosphor Ba9La2W4O24:Eu3+ with double perovskite structure and abnormal thermal quenching behavior

Abstract

In this work, a series of Eu³⁺ doped double perovskite phosphors Ba₉La₂W₄O₂₄:xEu³⁺ (0.2 ≤ x ≤ 1.0) were synthesized by a high temperature solid-state method. The phase purity and morphology features of phosphors were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Rietveld refinement was also executed and the results indicated that the cation site could provide a relative symmetrical environment, which will induce a large orange/red emission ratio. When excited by n-UV light, the phosphors could emit bright orange-red light with the strongest peak at 592 nm corresponding to the ⁵D₀–⁷F₁ transition. The optimal doping concentration of Eu³⁺ ions was x = 0.8 and the photoluminescence quantum yield could reach 82.9%. The concentration quenching effect was calculated to be dominated by the dipole–dipole interaction and transient spectrum results also gave direct evidence of the concentration quenching. At the operating temperature of the LED (145 °C), the photoluminescence emission intensity can still reach 97.16% at room temperature. The abnormal thermal quenching behavior was demonstrated to be compensated by electrons captured by traps. The satisfactory CIE coordinates, high color purity and strong emission intensity indicated that BLWO:0.8Eu³⁺ was a potential red phosphor for WLEDs with broad application prospects.