Luminescence enhancement in red-emitting MgMoO4:Eu3+ phosphor by partially combined substitution of Mg2+-Mo6+-O2− with Ca2+-W6+-F−.

A serial of red-emitting MgMoO₄: Eu³⁺ phosphors were synthesized via a high-temperature solid-phase approach. The effect of partially combined substitution of Mg²⁺-Mo⁶⁺-O²⁻ with Ca²⁺-W⁶⁺-F⁻ on the structure and luminescent properties of the MgMoO₄: Eu³⁺ phosphor was thoroughly investigated. The crystal structure of the as-prepared MgMoO₄: Eu³⁺ phosphor was not influenced by the partially combined Ca²⁺-W⁶⁺-F⁻ substitution. Under the excitation of 394 nm, The MgMoO₄: Eu³⁺ phosphor could emit bright red light centered approximately at 612 nm, corresponding to the ⁵D₀ → ⁷F₂ transition of Eu³⁺ and the optimal concentration of Eu³⁺ was about x = 0.10. After the partially combined Ca²⁺-W⁶⁺-F⁻ substitution, the luminescence intensity of Eu³⁺ ions was approximately 1.94 times of the initial values owing to the alteration of the crystal field and charge compensation. The thermal stability of the partially substituted phosphor was significantly enhanced and the emission intensity at 423 K was approximately 82.3% of the initial value at room temperature. The internal quantum efficiency of the partially substituted sample is about 49.5%. A white light-emitting diode (LED) manufactured by the partially substituted red Mg_0.7Ca_0.2Mo_0.8W_0.2O_3.8F_0.2: 0.10Eu³⁺, combined with commercial blue-green phosphors and 395 nm chips exhibits high performance featuring CCT = 5441 K and Ra = 88.7. These results mean that the partially combined Ca²⁺-W⁶⁺-F⁻ substitution in MgMoO₄: Eu³⁺ can be used to optimize luminescent properties of phosphors applied in white LEDs. [ABSTRACT FROM AUTHOR]