Chemistry Reference
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2+
replaced the Ca
sites in the host lattice. The excitation spectrum
showed a single broadband in the 300-450 nm region, as can be
seen from Fig. 6.10, where three broad peaks on the left of the graph
corresponded to the excitation spectrum of the three samples.
Comparison with the other two phosphors showed that
LiCaPO
2+
had the highest emission intensity, which was about
2.5 times that of LiSrPO
:Eu
4
2+
2+
:Eu
and 5 times that of NaCaPO
:Eu
.
4
4
LiSrPO
showed blue luminescence, but the emission peak
was slightly blue-shifted to 450 nm. Comparing with LiSrPO
:Eu
2+
4
2+
:Eu
4
2+
prepared by Wu
was found to have lower
sintering temperature for most efficient luminescence and had a
higher color rendering index. A blue phosphor with emission peak
at 470 nm had the optimum color rendering index [115].
et al
. [114], LiCaPO
:Eu
4
:Eu
2+
, LiCaPO
:Eu
2+
,
Figure 6.10
Excitation and emission spectra of LiSrPO
4
4
:Eu
2+
[113].
and NaCaPO
4
(b) Effects of dopant concentration on luminescence properties
As Eu
2+
concentration increased, the PL intensity of the blue
phosphors reached a peak, followed by a decrease in intensity
as critical quenching concentration was reached (Fig. 6.11).
The quenching concentration of LiCaPO
2+
:Eu
was found to be
4
2+
x
(concentration of Eu
) = 7 mol %. This was almost similar
2+
to LiSrPO
:Eu
and another phosphate-based blue phosphor
4
