Fluorescence feature of Ce

3+

and Tb

3+

in LnBO

3

and the energy transfer mechanism from Ce

3+

to Tb

3+

in borate have been systematically investigated.The quenching concentration of Ce

3+

in borate can be very heavy

for example at 0.1 mol and above in LaBO

3

.The green emission intensity of Tb

3+

is best when the concentration of Ce

3+

and Tb

3+

reaches 0.1 mol in LaBO

3

.The sensitization process of Tb

3+

ions by Ce

3+

ions in LnBO

3

is mainly energy transfer from Ce

3+

ions to Tb

3+

ions(

5

D

3

and

5

D

4

)with nonradiative resonance process.Electrons at

5

D

3

level transit into

5

D

4

level of Tb

3+

ion by cross relaxation.Thus the green emission(

5

D

4

-

7

F

7

544nm)intensity of Tb

3+

reaches the maximum when the concentration of Tb

3+

is at 0.1mol.In the case of heavy doping the blue emission(

5

D

3

-

7

F

7

)can not be seen.With surveying the fluorescence decay of Ce

3+

in borate doped with different concentration of Tb

3+

it is found that the experimental results accord well with theoretical values.The mechanism of nonradiative resonance energy transfer is found to be dipole-dipole interaction.The critical transfer distance R

0

is approximately 7.7Åand 6.5Åin LaBO

3

and GdBO

3

respectively.The probability and efficiency of the energy transfer have also been calculated.The efficiency of the energy transfer from Ce

3+

to Tb

3+

might leach 90% and above in LaBO

3

when the concentration of Ce

3+

and Tb

3+

is at 0.1 mol.Further research has indicated that energy diffuse within the sensitizer(Ce

3+

)affects the energy transfer process from Ce

3+

ions to Tb

3+

ions.