were synthesized at high temperature under weak reductive atmosphere. The XRD pattern of the sample shown that the product is the simple MgAl
2
O
4
phase. Photoluminescence (PL) excitation and emission
long-lasting phosphorescent (LLP) emission
decay curves
and thermostimulated-luminescence (TSL) spectra were used to characterize the powder phosphor. The sample emits green LLP emission at about 520 nm when excited by 209 nm. There are two ways of excitation energy: (1)Mn
2+
ions is excited directly under UV excitation between 279 nm and 451 nm
resulting in green photoluminescence; (2)For 209 nm excitation
Mn
2+
ionscharge transfer transition exists
so the electrons from the Mn
2+
ground state
6
A
1
are excited to the conduction band (CB). On one hand
the electrons in the CB can relax to the excited states of Mn
2+
through nonradiative processes
and then is green emission followed. On the other hand
some of the electrons in the CB can also be trapped in the electron traps
and then released at high temperature
then turned to the excited states of Mn
2+
through nonradiative processes
leading to the phenomenon of green LLP of Mn
2+
. The possible mechanism for this phenomenon of green LLP of MgAl
2
O
4
∶ Mn
2+
is also investigated based on the experimental results.
关键词
Keywords
references
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