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[Display omitted] • (Gd 0.95 Eu 0.05) 2 O 2 SO 4 monospheres and nanoplates were selectively synthesized from a new type of precursor. • The mechanism and kinetics of composition/phase/morphology evolution were clarified. • The monosphere phosphor emits ∼ 1.35 times as strong as nanoplates. • The monosphere phosphor has a high thermal stability of luminescence (∼81% at 150 °C) Rare-earth oxysulfates (RE 2 O 2 SO 4) attracted attention for large-capacity oxygen storage, low-temperature magnetism and luminescence, whose preparation mostly involves toxic SO x gases and/or complicated procedures. In the phosphor field, monospheres are preferred for a number of applications due to their better luminescence and high packing density. With the simple reactants of RE(NO 3) 3 , Na 2 CO 3 and (NH 4) 2 SO 4 for hydrothermal reaction, dispersed monospheres and nanoplates were selectively synthesized for the recently discovered RE 2 (OH) 2 CO 3 SO 4 · n H 2 O (RE = Gd 0.95 Eu 0.05 , REOCSH) layered compound precursor, from which RE 2 O 2 SO 4 phosphors mostly retaining their precursor morphologies were facilely derived via calcination in air at 800 °C, without involving SO x. Solution pH was found to decisively determine the chemical composition and crystallization kinetics of the initial precipitate, and the possible mechanisms of phase/morphology evolution during hydrothermal treatment were proposed by comparatively investigating the temperature-course and time-course of REOCSH formation under the typical pH values of 6 and 7. It was revealed that (Gd 0.95 Eu 0.05) 2 O 2 SO 4 monospheres emit ∼1.35 times as strong as nanoplates (λ ex = 257 nm, λ em = 617 nm) and may retain as high as ∼81% of the room-temperature intensity at 150 °C. The phosphor monospheres were also analyzed to have a fluorescence lifetime of ∼1.32 ms at room temperature and an activation energy of ∼0.19 eV for the thermal quenching of luminescence. [ABSTRACT FROM AUTHOR]

A series of well-dispersed (Ce 1- x Tb x)PO 4 (x = 0–1) microspheres, with an average diameter of ∼1.2 μm, have been originally prepared via two-phase interfacial precipitation and subsequent calcination. Characteristics of the as-synthesized and calcination products were investigated by the combined techniques of XRD, FE-SEM, TEM, FT-IR and TG-DSC. Under 275 nm excitation, tuning the emission color from blue (0.17, 0.02) to green (0.30, 0.56) was realized via varying the Tb3+ content and through Ce3+ → Tb3+ energy transfer. The optimal content of Tb3+ was found to be ∼15 at% (x = 0.15), and the energy transfer was determined to occur via electric dipole-dipole interaction. Moreover, both the emissions of Ce3+ and Tb3+ present gradually higher thermal stability with increasing Tb3+ content owing to enhanced energy transfer. The (Ce 0.85 Tb 0.15)PO 4 microspheres, which possess the highest absolute quantum efficiency (∼60.1%) across the series and excellent thermal stability (activation energy for thermal quenching of luminescence: ∼0.312 eV), may potentially serve as a single-phase green phosphor for solid-state lighting and field-emission display. Multi-color luminescent (Ce 1- x Tb x)PO 4 (x = 0–1) microspheres were successfully fabricated via gel/solution interfacial precipitation and subsequent calcination. Image 1 • (Ce 1- x Tb x)PO 4 (x = 0–1) microspheres were obtained via interfacial precipitation. • The formation mechanism of (Ce 1- x Tb x)PO 4 spheres was proposed. • Ce3+.→ Tb3+ energy transfer was analyzed to occur via dipole-dipole interaction • (Ce 0.85 Tb 0.15)PO 4 has favorable thermal stability for Tb3+ luminescence. [ABSTRACT FROM AUTHOR]

Abstract Eulytite-type Ba 3 La 1- x (PO 4) 3 : x Ce3+ (x = 0–0.10) and Ba 3- y La 0.97 (PO 4) 3 :0.03Ce3+, y Mn2+ (y = 0.05–0.30) phosphors were first synthesized via gel-combustion and subsequent calcination in an Ar/H 2 atmosphere at 1250 °C. Photoluminescence properties of the phosphors were thoroughly studied, including excitation, emission, emission color, thermal stability and the process of Ce3+ → Mn2+ energy transfer. The Ba 3 La(PO 4) 3 : x Ce3+, y Mn2+ phosphor series simultaneously exhibited the near-ultraviolet emission of Ce3+ (∼370 nm, 4 f 05 d 1 → 4 f 15 d 0 transition) and the orange-red emission of Mn2+ (∼591–605 nm, 4T 1 → 6A 1 transition) upon exciting the Ce3+ ions with ∼276 nm UV light. Owing to Ce3+ → Mn2+ energy transfer most probably occurring via dipole-dipole interaction, gradually enhanced Mn2+ while weakened Ce3+ emission was resulted at a higher Mn2+ content, with which the emission color can be adjusted from blue through reddish-purple and ultimately to orange red. The efficiency of the energy transfer was analyzed to reach its maximum of ∼43.2% at y = 0.30. It was shown that the Ba 3 La 1- x (PO 4) 3 : x Ce3+ and Ba 3- y La 0.97 (PO 4) 3 :0.03Ce3+, y Mn2+ phosphor series both have favorable thermal stabilities, whose activation energy for thermal quenching of luminescence was calculated to be ∼0.28 ± 0.02 eV for Ce3+ in the former while ∼0.22 ± 0.01 eV for Ce3+ and ∼0.21 ± 0.01 eV for Mn2+ in the latter system. Increasing temperature did not alter the emission wavelength of Ce3+ but gradually blue-shifted that of Mn2+ from ∼602 to 583 nm with increasing temperature from 25 to 200 °C. Graphical abstract Image 1 Highlights • Gel-combustion produced Ce3+ and Ce3+/Mn2+ doped Ba 3 La(PO 4) 3 phosphors. • Photoluminescence properties of the phosphors were thoroughly analyzed. • The mechanism and efficiency of Ce3+.→Mn2+ energy transfer were determined. • Favorable thermal stabilities were demonstrated for the phosphors. [ABSTRACT FROM AUTHOR]

A series of garnet-type Li 6 CaLa 2(1- x) Nb 2 O 12 : x RE phosphors (LCLN: x RE, RE = Pr, Sm, Tb and Dy) were prepared via sol-gel processing and subsequent calcination for the first time, with the course of phase evolution and the characteristics of the LCLN host and RE3+ luminescence being investigated in detail. It was found that ∼900–1000 °C is a suitable temperature for precursor calcination to produce the garnet phase and LCLN has a relatively low phonon energy (∼725 cm−1) and a relatively wide bandgap (∼4.53 eV) for luminescence. The LCLN:0.012Pr, LCLN:0.04Sm, LCLN:0.06 Tb and LCLN:0.06Dy typical phosphors were analyzed to have dominant excitation/emission bands at ∼278/489, 265/614, 268/549 and 264/581 nm, emission colors of white, orange, green and yellowish white, and fluorescence lifetimes of ∼0.43, 0.74, 0.90 and 0.44 ms, respectively. Temperature-dependent photoluminescence found that the four phosphors maintained ∼28, 37, 45 and 56% of their room-temperature intensities at 423 K, with activation energies for thermal quenching of ∼0.37, 0.29, 0.34 and 0.25 eV, respectively. The results demonstrated that the Li-stuffed LCLN garnet could be a suitable host for UV excitable multicolor phosphors. • ∼900–1000 °C is an appropriate temperature for precursor calcination to derive Li 6 CaLa 2 Nb 2 O 12 (LCLN) garnet. • The LCLN host is suitable for luminescence purposes. • The photoluminescence of Pr3+, Sm3+, Tb3+ and Dy3+ activators was comprehensively elaborated in LCLN. • The concentration quenching of Sm3+ luminescence in LCLN is dominantly resulted from electric dipole-dipole interaction. [ABSTRACT FROM AUTHOR]