Among the host lattices for luminescent material

orthosilicate and metasilicate compounds had been extensively investigated by many researchers because of their excellent chemistry stability

visible light transparency

and relative easy preparation. For example

Mn-doped Zn

2

SiO

4

phosphor which exhibits the highest emission intensity under VUV ray excitation have been intensely studied to be used for large plasma TV screens and the tricolor fluorescent lamp. In general

the phosphors doped with manganese activators have a long (decay) time according to the spin selection rule. The origin of the rather long decay time lies in the fact that the corresponding transition

4

T

1g

(G)

6

A

1g

(S) is spin forbidden. It is well known that the slow decay lifetime of Mn

2+

is a disadvantage for the Mn

2+

doped Zn

2

SiO

4

phosphor using as the green phosphor

however

a long (lifetime) is an important requirement for the afterglow phosphor

the long lifetime of Mn

2+

make it is feasible to be used as a activator ions in silicate host to create long-lasting phosphorescence. On the other hand

all the phosphors doped with manganese ions found up to now have short long-lasting phosphorescence

it is important to find an excellent silicate phosphor that can be applied to practical application. The aim of this work is to report on the long-lasting properties of Zn

2

SiO

4

:1.2%Mn

5%Cd phosphor. XRD analysis results show that the Zn

2

SiO

4

:1.2%Mn

5%Cd phosphors synthesized at 1050℃ for 3h are single phase and have no detectable amount of CdSiO

3

impurity. This phosphors show long-lasting phosphorescence under 240nm or (260nm) UV light for 3 min

the afterglow light can be seen by naked eye clearly in the dark room even after the excitation source have been removed for about 1 hour. The photoluminescence spectra measurement (revealed) that under excitation of 240 and 260nm radiation the luminescence center of Zn

2

SiO

4

:1.2%Mn

5%Cd phosphors do not changed because the emission spectrum have the same peaks position and shape. The bright green emission peaks located at～521nm is due to the

4

T

1g

(G)

6

A

1g

(S) transition of Mn

2+

ions.The chromaticity coordinates of this phosphor is

x

=0.2301

y

=0.6915. According to the luminescence decay curves measurement results

the Zn

2

SiO

4

:(1.2%Mn

)5%Cd phosphors show higher brightness compared to the Zn

2

SiO

4

:1.2%Mn phosphors

we considered that the Cd

2+

component in the Zn

2

SiO

4

:1.2%Mn

5%Cd phosphor results in the longer decay time because the ionic radius of Cd

2+

0.097nm is relative larger than that of Zn

2+

0.074 nm and the Cd

2+

is easy to lost during the high temperature synthesis. By introducing 5%Cd

2+

component to Zn

2

SiO

4

:(1.2%)Mn

some electron traps or crystal defects with appropriate trap depth can be created

and these traps result in the long-lasting phosphorescence.