Light‐induced electrons suppressed by Eu³⁺ ions doped in Ca_11.94−xSr_xAl₁₄O₃₃ caged phosphors for LED and FEDs

Abstract

Control of light-induced electron generation is of vital importance for the application of caged phosphors. For Eu-doped Ca 11.94Àx Sr x Al 14 O 33 caged phosphors, the suppressed effect of strontium doping on the light-induced electrons is observed compared to the europium-free Ca 11.94Àx Sr x Al 14 O 33 phosphors. In the presence of europium ions, Sr doping will promote the reduction of Eu 3+ to Eu 2+ . The Rietveld refinement suggests that unit cell volumes of the Ca 11.94Àx Sr x Al 14 O 33 :Eu 0.06 samples are expanded when Ca 2+ ions are replaced by Sr 2+ ions. The absorption and FTIR transmittance spectra confirm that the competitive reaction of encaged O 2À anions with H 2 is suppressed. For the sample (x=0.48), the higher thermal activation energy (~0.40 eV) for luminescence quenching can be attributed to the more rigid framework structure after Sr doping. For Ca 11.94Àx Sr x Al 14 O 33 :Eu 0.06phosphors, their emission colours are tuned from red to purple upon 254 nm excitation and from pink to blue under electron beam excitation through Sr substitution. The insight gained from this work may have a significant guiding to design new phosphors for LED and FEDs and novel nanocaged mutifunctional materials.

Enhancing emission intensity and thermal stability by charge compensation in Sr2Mg3P4O15:Eu3+

“…Figure A presents the PLE spectrum of Sr 2 Mg 3 P 4 O 15 :0.10Eu 3+ at room temperature. There was a broad asymmetric band in the range of 230‐300 nm, which represented the charge transfer (CT) band between 2p orbital of O 2‐ and the free 4f orbitals of Eu 3+ . Except for the CT band, the PLE spectrum also comprised several sets of strong to low sharp intensity lines in the range of 360‐550 nm.…”

“…Eu 3+ is an important rare‐earth ion with excellent properties and applies in many classic phosphors . The luminescence characteristics of Eu 3+ is based on the 5 D 0 ‐ 7 F J ( J = 0, 1, 2, 3, 4) transitions, and strongly depends on the symmetry of the crystal structure of the Eu 3+ occupied . In general, 5 D 0 ‐ 7 F 0 transition is forbidden and sensitive to the crystal field, which exhibits the emission only when Eu 3+ occupies sites with local symmetries of C n , C nv or C s .…”

Stabilization of divalent Eu2+ in fluorosilicate glass-ceramics via lattice site substitution

“…It thus becomes crucial to keep divalent Eu 2+ as the majority. Generally, there are several ways to transform Eu 3+ into Eu 2+ : (i) adding reducing agents, [10][11][12] (ii) inputting reducing atmosphere during preparation processes, 13,14 (iii) adjusting optical basicity or electronegativity of host, 15,16 (iv) substituting M 2+ sites in crystalline lattices. 17,18 As strategies (i) and (ii) accompany drawbacks such as introducing impurities into the system or leading to infeasibility for elaborated optimization of concentration and distribution of Eu 2+ , strategies (iii) and (iv) are usually considered to be more executable.…”

Improvement of self‐activated luminescence from introduced cation disorder in Sr6V2O11

“…Rare earth ion (RE)‐ or self‐activated phosphors have been widely investigated in engineering applications and basic sciences . Self‐activated phosphors present some advantages such as broad emission band, RE free, low sintering temperature, environment‐friendly (sintering in air), low cost, etc.…”

“…Rare earth ion (RE)-or self-activated phosphors have been widely investigated in engineering applications and basic sciences. [1][2][3][4][5][6] Self-activated phosphors present some advantages such as broad emission band, RE free, low sintering temperature, environment-friendly (sintering in air), low cost, etc. For example, self-activated vanadate is efficient luminescence material and has been paid considerable attention on solid-state lighting and display.…”