For the advanced study of the luminescence of Ce

3+

in various coordination environment served as are activater or sensitizer

the luminescence and energy transfer phenomena in hexagonal-Na

Ln

F

4

(

Ln

=La Gd or Y) doped with Ce

3+

Ce

3+

-Tb

3+

Ce

3+

-Eu

3+

have been investigated and some results are reported in this paper.The same luminescence centre of Ce

3+

formed in NaLaF4 and NaYF4 and the higher energy transfer efficiency of that in the host lattices are suggested from the fact that in the two host lattices Ce

3+

emits near 300nm with the close luminescence intensity and that the quenching concentration is very low for Ce

3+

in the flouride.A broad band with a max. emission peak at 420nm was observed in the host lattice of NaGdF

4

and the doped NaGdF

4

:Ce

3+

under the excitation of 273.5nm (Gd

3+

6

p-

8

S) and 250nm (only for NaGdF

4

at 77K and room temperature). Comparing the excitation and the emission spectra of NaGdF

4

and NaGdF

4

:Ce

3+

the relationship between the concentration of Ce

3+

and the luminescence intensity of the broad band and Gd

3+

in NaGd

1-x

Ce

x

F

4

(

x

=0

2.5

3.5

1) and the results-reported in some referencesthat the cation-defect centre or electron-self-trcped hole centre could be observed in some flou-rids especially containing Gd

3+

which could provide a shallow trap for electron

we suggest that one kind of cation-defect centre may exist in the NaGdF

4

host lattice (broad band emit in 420nm) and be sensitized by Ce

3+

and Gd

3+

through the pathway from (Ce

3+

→Gd

3+

) to cation-defect centre.