Ca

0.9

Sr

0.1

S:Bi

3+

Tm

3+

is a kind of codoped host mixing material. In this work

excitation spectra monitored at different wavelength from 440nm to 520nm

also emission spectra excited at different wavelength from 250nm to 350nm were obtained. Decay curves of the afterglow were measured at different emission position from 440nm to 520nm. UV excitation spectra showed that Tm

3+

's contribution to the Bi

3+

ion's

3

P

1

to

1

S

0

emission (at 453nm) came from 325nm of charge transfer transition. The Tm

3+

also acted as an electron-trapping center with its trap depth about 0.5eV. The decay kinetics of afterglow of the materials having both electron and hole trapping centers may be described as

I

t

=

I

0

[(1+γ

et

)(1+γ

ht

)]

-n

. In the case of Ca

0.9

Sr

0.1

S:Bi

3+

Tm

3+

γ

h

=0.0168

γ

e

=0.0001

n=1.1. Considering the linear relationship of the host mixing materials

the depth of the electron traps and the hole-traps can be written as

D

e

=β

e

-α

x

and

D

h

=(β

hc

-α

h

x)x+( β

hs

-α

h

x )(1-x ).