Layered Structure Produced Nonconcentration Quenching in a Novel Eu³⁺-Doped Phosphor

Energy migration (energy transfer among identical luminescence centers) is always thought to be related to the concentration quenching in luminescence materials. However, the novel Eu³⁺-doped Ba₆Gd₂Ti₄O₁₇ phosphor seems to be an exception. In the series of Ba₆Gd_2(1–x)Ti₄O₁₇:xEu³⁺ (x = 0.1, 0.3, 0.5, 0.7, and 0.9) phosphors prepared and investigated, no concentration quenching is found. Detailed investigations of the crystal structure and the luminescence properties of Ba₆Gd_2(1–x)Ti₄O₁₇:xEu³⁺ reveal that the nonoccurrence of concentration quenching is related to the dimensional restriction of energy migration inside the crystal lattices. In Ba₆Gd₂Ti₄O₁₇, directly increasing the number of Eu³⁺ ions to absorb as much excitation energy as possible allows to achieve a higher brightness. The highly Eu³⁺-doped Ba₆Gd_2(1–x)Ti₄O₁₇:xEu³⁺ (x = 0.9) sample can convert near-UV excitation into red light, whose Commission Internationale de l’Eclairage (CIE) coordinates are (0.64, 0.36) and the color purity can reach up to 94.4%. Moreover, warm white light with the CIE chromaticity coordinates of (0.39, 0.39), the correlated color temperature of 3756 K, and the color rendering index of 82.2 is successfully generated by fabricating this highly Eu³⁺-doped phosphor in a near-UV light-emitting diode chip together with the green YGAB:Tb³⁺ and blue BAM:Eu²⁺ phosphors.