Multi-color mechano-luminescence of LaGaO_(3):Sm^(3+),Tb^(3+) via trap sharing for anti-counterfeiting and encryption

Mechano-luminescence(ML) has been found diverse applications such as stress sensing,3-D signature,energy harvesting,and anti-counterfeiting,due to the unique properties of the corresponding ML phosphors performing in-situ and real-time response to mechanical stimulus.Trap-controlled ML materials realize reproducible,quantitative mechano-optical conversion resulting from the released carriers for the trap-mediated charge storage and release.Herein,modulating traps matters the controllable ML behavior for their promising applications.In this work,a deep trap distributed ranging from 0.9 to 1,3 eV is realized consecutively for the introduction of Sm^(3+)ions into LaGaO_(3) matrix,which contributes to the red emission at 600 nm under mechanical stimuli.Moreover,tunable ML emission modulated from 600to 545 nm is successfully achieved for the codopant of Tb^(3+)ions.It is unambiguously indicated that the released carriers from the trap sharing rather than an additional constructed trap contribute to the modulated ML color.Accordingly,multi-mode anti-counterfeiting and encryption are achieved with the as-explored Sm^(3+),Tb^(3+)co-activated ML phosphor.

Fabrication and photoluminescence characteristics of novel red-emitting Ba_(2)LuNbO_(6):Eu^(3+)double-perovskite phosphors on near UV WLEDs

Red emitting phosphors play a significant role in accelerating the improvement of illumination quality for white light emitting diodes(WLEDs).In this work,by using solid-state reaction method,an efficient novel Ba_(2)LuNbO_(6):Eu^(3+)phosphor with double-perovskite structure was successfully prepared.Here,a series of Ba_(2)LuNbO_(6):Eu^(3+)red phosphors can be efficiently pumped by the near-ultraviolet(UV)light and then present high-brightness at orange emission(598 nm,~5D_(0)→~7 F_(1))and red emission(610 nm,~5D_(0)→~7 F_(2)).The ratio values of 610 to 598 nm in Ba_(2)LuNbO_(6):Eu^(3+)phosphors exceed 1 when the content of Eu^(3+)is larger than 0.4 mol,because the occupation of Eu^(3+)ions is changed from Lu^(3+)ions with symmetric sites to Ba^(2+)ions with asymmetric sites.Besides,the optimized concentration of Eu^(3+)at the~5D_(0)→~7 F_(2)transitions is obtained when x=1,indicating that there is non-concentration quenching in Ba_(2)LuNbO_(6):Eu^(3+)phosphors.Moreover,the CIE chromaticity coordinates of Ba_(2)LuNbO_(6):Eu^(3+)was calculated to be(0.587,0.361),the color purity was calculated to be 72.26%and internal quenching efficiency(IQE)was measured to be 67%.Finally,the thermal stability of Ba_(2)LuNbO_(6):Eu^(3+)phosphors was also studied.Our work demonstrates that the novel double-perovskite red-emitting Ba_(2)LuNbO_(6):Eu^(3+)phosphors are prospective red emitting elements for WLEDs applications.