Search

Lactic acid (LA) was originally employed as a cosolvent for solvothermal synthesis of LaPO4:Ce3+, Tb3+, Sm3+ nanocrystal phosphors, whose effect on crystal growth was revealed by the combined techniques XRD, FE-SEM and TEM. It was shown that LA not only remarkably restricted the intrinsic one-dimensional (1D) growth of hexagonal LaPO4 crystals along the [001] direction, resulting in a shape variation from microwires to nanoparticles, but also promoted crystallite growth. With more efficient Ce3+ → Tb3+ energy transfer resulting from larger crystallite size, the h-(La0.90Ce0.05Tb0.05)PO4 nanoparticles presented more intense and thermally stable green emission of Tb3+ as compared to the nanowires. Moreover, a series of (La0.93−xCe0.05TbxSm0.02)PO4 (x = 0–0.40) nanocrystals, with the emission color varying from blue to green and eventually to yellow, were successfully prepared through adjusting the concentration of Tb3+, in which the Tb3+ ion acted as an energy transfer bridge between Ce3+ and Sm3+. The mechanism of Ce3+ → Tb3+ → Sm3+ energy transfer was proposed, and the optimal Tb3+ content for Sm3+ emission was determined to be x = 0.20. The optimized (La0.73Ce0.05Tb0.20Sm0.02)PO4 phosphor exhibited good thermal stability for Sm3+ emission, whose activation energy for thermal quenching was found to be ∼0.33 eV. [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]

● Multiform (Y 0.95 Eu 0.05)PO 4 crystals were attained via hydrothermal reaction. ● Increasing MA content leads to a tetragonal (t-) to hexagonal (h-) phase transition. ● A higher pH or PO 4 3- content favors the crystallization of t-(Y 0.95 Eu 0.05)PO 4. ● The (Y 0.95 Eu 0.05)PO 4 phosphors showed structure/morphology-dependent luminescence. [Display omitted] With maleic acid (MA) as an original and efficient structure/morphology modifier, tetragonal (t-) and hexagonal (h-) structured (Y 0.95 Eu 0.05)PO 4 nano/microcrystals with the diverse morphologies of nanoparticles, nanospindles, nanosquares, nanodisks and microprisms have been successfully synthesized via hydrothermal reaction at 180 °C for 24 h. The systematic study demonstrated that solution pH, MA/(Y 0.95 Eu 0.05)3+ molar ratio and PO 4 3-/(Y 0.95 Eu 0.05)3+ molar ratio are three crucial factors that synergistically determine phase structure and crystal shape/size of the product, and the underlying mechanisms were proposed. Photoluminescence of the (Y 0.95 Eu 0.05)PO 4 crystals was revealed to be strongly morphology/structure dependent, which was discussed in detail in terms of excitation, emission, asymmetry factor of luminescence, quantum yield, fluorescence decay, emission color and thermal stability. [ABSTRACT FROM AUTHOR]