Controllable Eu²⁺-Doped Orthophosphate Blue-/Red-Emitting Phosphors: Charge Compensation and Lattice-Strain Control

Abstract

Cation-substitution-induced controllable luminescence tuning could efficiently optimize and improve the luminescence performances of novel phosphor materials for realizing high-quality lighting. As important members of the orthophosphate family, ABPO4 (A = alkali metal Li, Na, K, Rb, Cs; B = alkali earth metal Mg, Ca, Sr, Ba) offers an abundant cation lattice environment for rare earth ions. Herein, we successfully prepared a broad-band red-emitting CsMgPO4:Eu2+ phosphor with an emission peak at 628 nm (fwhm = 118 nm). A series of cation-substitution strategies are designed to adjust and enhance its luminescence performances. The corresponding mechanisms are also investigated and proposed reasonably. A charge-compensation strategy of [Eu2+-Si4+] → [Cs+-P5+] could dramatically enhance the quenching concentration from 0.04 to 0.30, which is attributed to the decrease of Eu3+. Two cation-substitution strategies of larger Ba2+ (Sr2+) ions for Mg2+ ions could achieve superior emission adjustment of Eu2+ ions from the red to blue (yellow) region due to local lattice distortion. Interestingly, a consecutive emission adjustment from the red to blue region by simply changing the annealed temperature is reported for the first time, and the possible emission tuning mechanism is revealed based on a local lattice-strain control. This study could serve as a guide in developing Eu2+-activated ABPO4 phosphors with improving luminescence performance and controllable luminescence adjustment based on charge compensation and lattice-strain control through various cation substitutions.

A new type of phosphate-based phosphor Na3CsMg7(PO4)6:Eu2+/Mn2+with high quantum efficiency and high thermostability

“…Nonetheless, some exceptions such as a small amount of Eu 2+ in the Cs + sites cannot be entirely avoided, which have been found in other phosphors such as CsMgPO 4 : Eu 2+ . 34 If there exist two luminescent centers, Cs Eu 2+ and Na Eu 2+, there must be two distinct luminescent emitting bands. However, from the following studies, this possibility can be ruled out.…”

In‐air self‐reduction synthesis and luminescence properties from Mg21Ca4Na4(PO4)18:Eu2+–Eu3+ excited using ultraviolet light

“…Most Eu 2+ is obtained by reducing gases or by adding some reductive substances. [14][15][16] However, this method has high requirements on carrier gas equipment and has certain risks. Su Qiang [17] and colleagues proposed the principle of unequal substitution and obtained Eu 2+ through self-reduction [18][19][20] mechanisms.…”

Tuning Emission Spectrum of KSrPO4:Eu2+ Phosphor by Co-Doping with Y3+

“…However, in the case of ABPO 4 -type host, Eu 2+ ions tend to substitute B 2+ in ABPO 4 due to the preference of similar ionic radius and valence state between Eu 2+ and substituted sites [13,14]. In addition, B 2+ has only one kind of sites in CsMgPO 4 , KBaPO 4 , KSrPO 4 , and LiMgPO 4 lattices, leading to one luminescence center of Eu 2+ [15][16][17][18].…”