Uniform colloidal spheres for RE₃BO₆ (RE = Eu‐Yb, Y) and excitation‐dependent luminescence of Y₃BO₆:Eu³⁺ red phosphor

Abstract

Phosphor particles of spherical shape and uniform size are desired for high‐definition displays to improve the resolution and the overall luminescent performance. However, the synthesis of RE3BO6 spherical particles is a considerable challenge in materials science. Here, uniform spheres of RE3BO6 (RE = Eu–Yb, Y) have been converted from their colloidal precursor spheres synthesized via homogeneous precipitation. The amorphous precursor spheres are solid particles with decreased boron going from the surfaces to the cores. Smaller particles were observed at decreased ionic radius from Eu3+ to Ho3+ (including Y3+), but particles with nearly unvaried sizes were observed by further decreasing the ionic radius from Ho3+ to Yb3+. They crystallized in monoclinic RE3BO6 at 900°C, with maintaining the spherical shape of precursors. However, the crystal growth and the densification toward the particle surfaces resulted in the formation of hollow spheres for smaller particles and core‐shell structured spheres for larger particles. The parameters, a, b, and c, increase nearly monotonically with increasing the radius of rare earth ions. The uniform spheres of Y3BO6:Eu3+ exhibited a typical red emission at ~613 nm (5D0 → 7F2 electric dipole transition of Eu3+), with an intensity ratio I(5D0 → 7F2)/I(5D0 → 7F1) of ~3.5. The luminescence behavior of Y3BO6:Eu3+ phosphor is dependent on the excitation wavelength, which is closely related to the Eu3+ ions at different coordination sites. Driven by a 460‐nm blue‐LED chip, the Y3BO6:Eu3+ spheres exhibited a red emission with the CIE coordinates of (~0.65, ~0.35), indicating that they are an excellent red‐emitting phosphor candidate for application in white‐LEDs.

A Two-Dimensional Guidance Strategy to Fabricate Perovskite Gadolinium Aluminate Ceramic Film

“…Transmittance of the prepared GAP:Eu 3+ ceramic film was analyzed in Figure 5c. A broad and strong band is found in the transmittance curve at the range of 250-400 nm, which is arising from the charge-transfer absorption of O 2− -Eu 3+ [32]. The shoulder near the intense band is assigned to the 8 S 7/2 -6 I J transition of Gd 3+ [33].…”

“…Monitoring the wavelength at 618 nm, a broad and strong band is observed in PLE spectra at the range of 200-300 nm, whose maximum is located at 254 nm. The electron transition of O 2− -Eu 3+ mainly contributes to the intense band (Figure 6a), which is usually called the charge-transfer band (CTB) [32]. However, the very weak peaks at the wavelength range of 300-500 nm are assigned to the intra-4f electronic transitions of the Eu 3+ ion, but they are almost invisible because of the rather strong CTB.…”

“…Under the UV light excitation at 254 nm, the GAP:Eu 3+ transparent ceramic film outputs a red emission with multiple sharp peaks. The emission peaks at the range of 500-800 nm are assigned to the typical transition of Eu 3+ from the excited energy level of 5 D 0 to the ground energy level of 7 F J (J = 0, 1, 2, 3, 4) [32]. Because the relative intensity of different J-level transitions is closely related to the symmetrical environment of Eu 3+ ion, the coordination environment of Eu 3+ in the host can be evaluated by the intensity of Eu 3+ transitions.…”

High quantum efficiency and excellent color purity of red-emitting Eu3+-heavily doped Gd(BO2)3-Y3BO6-GdBO3 phosphors for NUV-pumped WLED applications

“…8 It was previously reported that GdBO 3 , 17–19 Gd(BO 2 ) 3 , 20 and Y 3 BO 6 (ref. 21 and 22) are excellent host lattices to dope a high amount of Eu 3+ ions; however, only a low quantum efficiency of 14.30% could be obtained under the excitation of NUV light. It is well known that the introduction of dopants at a critical concentration in a material often leads to a decrease in photoluminescence (PL) intensity, resulting in a lower quantum efficiency of the synthesized material.…”

Evaluation of Mechanical and Thermal Performance of Polyethylene Terephthalate Recycled Ribbon and Carbon‐Reinforced Compatibilized Polypropylene

“…Compared to uncompatibilized blend due to the elastomeric nature of SEBS in SEBS-g-MAH. Zhu et al [6] carried out a research on PP/PET (80/20 wt.) blend with polypropylene grafted maleic anhydride and diallyl phthalate(PP-g-MAH/DAP) as a compatibilizer and observed better size distribution, dispersion, better mechanical properties with respect to the uncompatibilized PP/recycled PET blend.…”