The Tb

3+

ion can emit the green fluorescence

it is interesting one of elements for luminescent material. The fluorescence of Tb

3+

originates from the transitions between

5

D

3

and

5

D

4

energy levels

the fluorescent range are about 380-680nm

the transition of

5

D

4

-

7

F

5

of Tb

3+

ion is the strongest at 542nm

which can be considered as a standard wavelength of green color in luminescence. The blue light comes from

5

D

3

energy level

which influences the purity of light color

therefore

it is necessary to improve the fluorescent color.As known

it is possible to increase the concentration of Tb

3+

for improving ligth color

because there are the cross relaxation between

5

D

3

-

5

D

4

and

7

F

6

-

7

F

0

energy level pairs. However

it is hard to get high concentration of Tb

3+

in the luminescent material

so there are stronger blue color in the fluorescence of Tb

3+

. We have tried to improve light color in pan-taphosphate and found a new quenching element Tm

3+

to the fluorescence of

5

D

3

energy level of Tb

3+

the quenching machanism is considered to be cross relaxation process between energy level pair

5

D

3

-

5

D

4

of Tb

3+

ion and energy level pair

3

H

6

-

3

F

4

of Tm

3+

ion. In this paper

the fluorescent spectra of erystals were measured for variant concentration and used to calculate the cross relaxation probability and the dependence between fluorescent intensities and the concentrations of Tm

3+

and Tb

3+

ions. We compared these fluorescent intensities with the fluorescence of pure Tb

3+

in crystals.