VUV photoluminescence of (Gd,Zn)PO4:Tb3+ phosphors synthesized by ultrasonic spray pyrolysis

High-quality (Gd0.955−xZn0.045)PO4:xTb3+ (0.06≤x≤0.15) green phosphors were synthesized by ultrasonic spray pyrolysis. With an increase of Tb3+ content, the emission intensities caused by the 5D4→7FJ (J = 3, 4, 5, and 6) and 5D3→7FJ (J = 4, 5, and 6) transitions of Tb3+ increased and decreased, respectively, allowing a purer green emission. The emission intensity of (Gd0.805Zn0.045)PO4:0.15Tb3+ at 544 nm was 53.0% stronger than that of (Gd0.895Zn0.045)PO4:0.06Tb3+. The emission intensity and the green color purity were remarkably improved by increasing Tb3+ content in (Gd0.955−xZn0.045)PO4:xTb3+.