Key Role Effect of Samarium in Realizing Zero Thermal Quenching and Achieving a Moisture-Resistant Reddish-Orange Emission in BaLaNbO:Sm.

The strategy to enhance phosphor stability against thermal quenching and moisture conditions will contribute to controlling the feature of phosphor-converted white-light-emitting diodes (pc-WLEDs). Herein, an effective strategy is achieved with the incorporation of Sm ions, and a robust reddish-orange emission (no thermal quenching up to 498 K) is obtained based on BaLaNbO as a host. In light of excitation by near-ultraviolet irradiation at 408 nm, BaLaNbO:Sm gives rise to a typical signal ascribed to the G → H ( = 5, 7, 9, and 11) transitions of Sm ions. The concentration quenching effect is observed when the Sm content exceeds 10%, and the quenching mechanism is caused by electronic dipole-dipole interactions. Based on the narrow emission curves, a very high color purity (92.4%) could be recorded. The Sm substitution at the Ba/La site leads to a rigid structural lattice and abundant electron-trapping centers for the Sm ions, which will be responsible for the zero-thermal-quenching phenomenon. In addition, oleic acid (OA) is selected to form a hydrophobic covering surface structure to protect BaLaNbO:Sm, which can assist in improving the moisture resistance. The most favorable parameters concerning the warm-light emission (a high general color rendering index, Ra, of 85.7 and a low correlated color temperature, CCT, of 4965 K) can be achieved in pc-WLEDs containing an OA-modified sample. Moreover, its luminous efficiency, LE, can maintain 82.9% of its initial value after 120 h under controlled environmental conditions of 85 °C and 85% humidity. These results pave a new way to optimize the sample as a potential candidate for red-emitting materials.