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

Control of light-induced electron generation is of vital importance for the application of caged phosphors. For Eu-doped Ca_11.94−xSr_xAl₁₄O₃₃ caged phosphors, the suppressed effect of strontium doping on the light-induced electrons is observed compared to the europium-free Ca_11.94−xSr_xAl₁₄O₃₃ phosphors. In the presence of europium ions, Sr doping will promote the reduction of Eu³⁺ to Eu²⁺. The Rietveld refinement suggests that unit cell volumes of the Ca_11.94−xSr_xAl₁₄O₃₃:Eu_0.06 samples are expanded when Ca²⁺ ions are replaced by Sr²⁺ ions. The absorption and FTIR transmittance spectra confirm that the competitive reaction of encaged O²⁻ anions with H₂ 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_11.94−xSr_xAl₁₄O₃₃:Eu_0.06 phosphors, 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.