Abstract:The role of charge compensatory additives viz. monovalent ions (Li 1 , K 1 , and Na 1 ) codoped with Tb 31 in strontium silicate phosphors is investigated. The addition of charge compensators enhances the luminescence intensity of the prepared phosphors because they neutralize the charge generated by Tb 31 substitution for Sr 21 ions. The vacancy and defects created due to Tb 31 ions are suitably minimized by the addition of aliovalent impurities in the host. As the Tb 31 concentration is increased, the green … Show more
“…This in turn influences the spin-orbit coupling and the crystal field of europium ions. Thus, the relative emission intensity of the phosphors incorporated with lithium is strongly enhanced as the coordination conditions of europium ions are influenced due to the change in distances between Eu-O [28,29].…”
“…This in turn influences the spin-orbit coupling and the crystal field of europium ions. Thus, the relative emission intensity of the phosphors incorporated with lithium is strongly enhanced as the coordination conditions of europium ions are influenced due to the change in distances between Eu-O [28,29].…”
“…Note that depending on substitutions, the crystal structure of the host could be stabilized or destabilized. Furthermore, the difference in ionic valency (D y 3+ /Tb 3+ and Ca 2+ ) may result in the uncompensated ions [32], which is the so-called ‘aliovalent effect’ and is considered as future work. Figure 1( a ) XRD patterns of Ba 1.3 Ca 0.7- x - y SiO 4 : x D y 3+ / y Tb 3+ ( x = 0.03 and y = 0.00–0.05) crystals.…”
The
τ
-phase Ba
1.3
Ca
0.7-
x
-
y
SiO
4
:
x
D
y
3+
/
y
Tb
3+
phosphors co-doped with D
y
3+
(
x
= 0.03) and Tb
3+
(
y
= 0.01–0.05) trivalent rare-earth ions were prepared by the gel-combustion method. The structure–property relation of the samples was examined by X-ray diffraction, scanning electron microscopy and spectrophotometer. Here, the effect of Tb
3+
's concentration on the spectroscopic properties of Ba
1.3
Ca
0.7-
x
-
y
SiO
4
:
x
D
y
3+
/
y
Tb
3+
phosphors was explored by using the photoluminescence excitation, emission and decay curves. Importantly, the photonic energy transfer from (D
y
3+
:
4
F
9/2
+ Tb
3+
:
7
F
6
) to (D
y
3+
:
6
H
15/2
+ Tb
3+
:
5
D
4
) was observed, in which the D
y
3+
ions act as a light-emitting donor whereas the Tb
3+
ions as a light-absorbing acceptor, resulting in an enhanced emission from the co-doped Ba
1.3
Ca
0.7-
x
-
y
SiO
4
:
x
D
y
3+
/
y
Tb
3+
(
x
= 0.03 and
y
= 0.01–0.05) phosphors. Finally, the chromaticity coordinates were determined from the measured emission spectra, locating at the green and white light regions. This observation indicates that the characteristic emission colour could be tuned from white to green by varying Tb
3+
concentrations under ultraviolet light.
“…This could be explained that the radius of Li + is smaller, which makes Li + enter the lattice more easily and the lattice distorts little, and thus improving the transitions of Eu 3+ . 43,44 Besides the emission spectra, the QE of CaSr 1.92 Al 2 O 6 :0.08Eu 3+ was also measured and calculated; the commercial YAG:Ce phosphor (com-YAG:Ce) was used as a reference. The QEs of CaSr 1.92 Al 2 O 6 :0.08Eu 3+ and com-YAG:Ce are 26.3% and 89.7%, respectively.…”
The novel red-emitting phosphors of Eu 3+ -activated CaSr 2 Al 2 O 6 :Eu 3+ were synthesized by conventional solid state reaction. Crystal structure, characteristic luminescence properties and charge compensators effect (Li + , Na + , K + ) are investigated in detail by X-ray diffraction refinement and photoluminescence spectra measurement. CaSr 2 Al 2 O 6 crystallizes in a cubic structure with the space group of Pa(3)-205, and cell parameter a = b = c = 15.06217(5)Å. The difference between the emission spectra of CaSr 1.90 Al 2 O 6 :0.10Eu and Ca 0.90 Sr 2 Al 2 O 6 :0.10Eu revealed that the Eu 3+ ions occupied nonequivalent Sr 2+ or Ca 2+ sites with different site symmetry. When Eu 3+ ions occupied Sr 2+ sites without inversion symmetry, the intensity ratio of ( 5 D 0 -7 F 2 )/( 5 D 0 -7 F 1 ) is higher and thus a better color purity. CaSr 1.92 Al 2 O 6 :0.08Eu 3+ exhibits strong absorption at 394 nm and intense red emission with CIE chromaticity coordinates (0.6408, 0.3581). The critical distance of the concentration quenching and thermal stability are also investigated.
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