White-light emitting single-phase phosphor La_3Si_6N_(11):Dy^(3+),Tb^(3+):Color tunable emission, thermal stability and energy transfer process

A novel white-light emitting single-phase phosphor La_3 Si_6 N_(11):Dy^(3+),exhibiting two emission peaks centering at 475 and 575 nm, was prepared via conventional solid-state reactions. The structure and morphology of La_3 Si_6 N_(11):Dy^(3+)/Tb^(3+) were investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The emission colors can be tuned from white to yellow-green through increasing the Tb^(3+) concentration in La_3 Si_6 N_(11):Dy^(3+),Tb^(3+), The mechanism of energy transfer(ET) from Dy^(3+) to Tb^(3+) is confirmed according to the excitation,emission spectra and decay lifetimes curve. The temperaturedependent luminescence measurements of La_(2.83)Si_6 N_(11):0.1 Dy^(3+),0.07 Tb^(3+) were also performed, and a good thermal stability is shown, suggesting superior properties for the application as white lightemitting diodes(w-LEDs) phosphor.

Broadband near-infrared luminescence and energy transfer of Cr^(3+),Ce^(3+) co-doped Ca_(2)LuHf_(2)Al_(3)O_(12) phosphors

Broadband near-infrared phosphors are highly desirable for food testing.Targeted Ca_(2)LuHf_(2)Al_(3)O_(12):Cr^(3+)(CLHA:Cr^(3+)) and Ca_(2)LuHf_(2)Al_(3)O_(12):Ce^(3+),Cr^(3+)(CLHA:Ce^(3+),Cr^(^(3+))) phosphors were synthesized by the conventional high-temperature solid state reaction.The CLHA:Cr^(3+)phosphor,with a good thermal stability,shows a red shift owing to radiation reabsorption and non-radiative transition with increasing Cr^(3+)content.For co-doped sample,the emission intensity of Cr^(3+)can be enhanced by three times due to the energy transfer from Ce^(3+)to Cr^(3+),which can be evidenced by a significant overlap between the PLE of Cr^(3+)single-doped phosphor and the PL of Ce^(3+)single-doped phosphor.In addition,the mechanism of energy transfer is identified as a quadrupole-quadrupole interaction according to decay Lifetime and Dexter’s energy transfer formula.The broadband NIR emission peaked at 775 nm of CLHA:Cr^(3+),Ce^(3+)phosphor shows a bright prospect in nondestructive quality-control analysis systems for food.

Effect of fluxes on synthesis and luminescence properties of BaSi_2O_2N_2:Eu^(2+) oxynitride phosphors

Eu^2＋ activated BaSi2 O2 N2 oxynitride bluish-green phosphor was synthesized adopting conventional high-temperature solid-state reaction method, in which BaF2, Na2 CO3 and NH4 Cl were used as the fluxes.The phase formation, size distribution and microscopic morphology were characterized to investigate the influence of adding fluxes on photo luminescence properties. The results indicate that with the addition of BaF2 flux, the particle morphology becomes regular and size distribution narrows and the phase purity of BaSi2 O2 N2：Eu^2＋ phosphor can be improved effectively. The photoluminescence intensity of BaSi2 O2 N2：Eu^2＋ phosphor with BaF2 as flux gets enhanced obviously, which is much higher than that of Na2 CO3, NH4 Cl and without flux. The optimum content of BaF2 flux is 4 wt%, and the maximum photoluminescence intensity of the BaSi2 O2 N2：Eu^2＋ phosphor prepared with BaF2 flux rises to 141%,meanwhile, the phosphors with BaF2 flux exhibits low thermal quenching. The results indicate that the BaSi2 O2 N2：Eu^2＋ is sort of promising bluish-green phosphor for application in full-spectra LED.