Layered Structure Produced Nonconcentration Quenching in a Novel Eu 3+ -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 Eu ³⁺ -doped Ba ₆ Gd ₂ Ti ₄ O ₁₇ phosphor seems to be an exception. In the series of Ba ₆ Gd _{2(1- x)} Ti ₄ O ₁₇ : xEu ³⁺ ( 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 Ba ₆ Gd _{2(1- x)} Ti ₄ O ₁₇ : xEu ³⁺ reveal that the nonoccurrence of concentration quenching is related to the dimensional restriction of energy migration inside the crystal lattices. In Ba ₆ Gd ₂ Ti ₄ O ₁₇ , directly increasing the number of Eu ³⁺ ions to absorb as much excitation energy as possible allows to achieve a higher brightness. The highly Eu ³⁺ -doped Ba ₆ Gd _{2(1- x)} Ti ₄ O ₁₇ : xEu ³⁺ ( 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 Eu ³⁺ -doped phosphor in a near-UV light-emitting diode chip together with the green YGAB:Tb ³⁺ and blue BAM:Eu ²⁺ phosphors.