Thermal Stability Enhancement by a Cationic Substitution Strategy in Red-Emitting Eu₂W3–xMoxO₁₂ Solid-Solution Phosphors

Superior thermal stability is an essential property of phosphor materials for their practical applications in the white-light-emitting diode (pc-WLED) lighting area. Nevertheless, the development of thermally stable red phosphor remains a challenging issue due to the serious nonradiative transition loss. In this work, a series of red-emitting Eu2W3–xMoxO12 (0.0 ≤ x ≤ 3.0) solid-solution phosphors were synthesized based on high-temperature solid-phase reaction. Surprisingly, the thermal stability property is obviously improved by designing a cationic substitution strategy and adjusting the annealing temperature. Under near-ultraviolet light excitation (395 nm), the emission intensity of Eu2W3O12 and Eu2Mo3O12 at 125 °C is 0.63 and 1.36 times of that at 25 °C, respectively. The emission intensity of Eu2Mo3O12 at 125 °C is increased to 2.16, which exhibits more competitive thermal stability than Eu2W3O12. This unique antithermal quenching enhancement phenomenon is ascribed to the decreased thermal ionization and thermally activated crossover effect energy, resulting from the simultaneously increased optical band gap and activation energy via the cationic substitution strategy. This work proposes a strategy to optimize the thermal stability behavior of red phosphors in pc-WLED applications.