The phosphors of Sr

4

Al

14

O

25

:RE

3+

(RE=Eu

Ce

Tb) were sy nthesized by high-temperature solid state reaction.The doping ions all occupy two different sites in the matrix. The two charge transfer bands and two

5

D

0

7

F

0

emission lines in the spectra shows that Eu

3+

ions occupy two latticlsites in Sr

4

Al

14

O

25

:Eu

3+

.In the excitation spectrum of Sr

4

Al

14

O

25

:Ce

3+

there are two broad bands at 265 and 335nm resp ectively

due to the transitions from the ground states of

2

F

5/2

and

2

F

7/2

to the excited state of 5d.Because of the large overlap between the emission bands

we couldnt separate them from each other

even reducing the slit width.We could get two bands at 362 and 385nm with the Gaussian-fitted method by origin soft. The energy difference between them is 1650cm

-1

lower than that of

2

F

5/2

and

2

F

7/2

viz. 2000cm

-1

as usual.The intensity of 385nm band relative to that of 362nm in the case of 335nm excitation is stronger than that in the case of 265nm excitation

which might be due to the energy transfer from the 362nm band to the 385nm band.Similar phenomenon appeared in the phosphor of Sr

4

Al

14

O

25

:Eu

2+

.In Sr

4

Al

14

O

25

:Tb

3+

the emission spectra are different from each other in the cases of the excitations at 235 and 241nm.At the excitation of 235nm

the 382nm band is the strongest emission peak

while at the excitation of 241nm

the 545nm one instead of it.The above analyses confirmed that these three ions all had two light centers

just like Eu

2+

ions in this host.The emissions from the levels of

5

D

3

and

5

D

4

of Tb

3+

appear at the same time

which shows that the non-radiative process between them is inefficient.In the excitation spectrum of the Tb

3+

emission of Sr

4

Al

14

O

25

:Ce

3+

Tb

3+

sample

there are not only the absorption of Tb

3+

but also the absorption of Ce

3+

which shows that Ce

3+

could sensitize Tb

3+

. And the energy transfer from Ce

3+

to Tb

3+

is not complete because the emission spectrum consists of both Ce

3+

and Tb

3+

emissions.