A study was made on the spectral structure characterization and valence stability of Eu

2+

ions in

AR

F

4

(

A

=Na

K;

R

=La

Gd

Lu and Y)

one of complex fluorides useful as multifunctional materials.Alkali metal ions have the lowest ionizing potential and highest positive electricity and stronger ionic bond is formed easily in its compounds.The Eu

2+

ion probably is given priority to occupy a alkali ionic lattice site in the complex fluorides synthesized by alkali and rare earth fluorides because the alkali ions have smaller electronegative and longer ionic radius than Eu

2+

ion.Systemic compounds of this complex fluorides were synthesized with successive firing in a stream of high purity argon (0.51/min) in the temperature range of 550-800C. However

compounds of systems AF-Rf

3

(

A

=Rb

Cs;

R

=La

Gd

Lu and Y) were not obtained.A sharp peak at 360 nm was observed in the fluorescence emission structure of Eu

2+

-doped

AR

F

4

when

R

=Gd

Lu or Y at 300K

or

R

=La at 77K. The emission arises from 4f

7

(

6

P

7/2

)-4f

7

(

8

S

7/2

) transition of Eu

2+

ions. In addition to sharp peak emission

broad band was observed at 396nm. In concordance with criterion of electronic transition of Eu

2+

ion in complex fluorides

both d-f and f-f transitions could be observed

with the energy difference between absorption bottom of 4f-5d and centre of gravity for

6

P

7/2

being smaller than 300cm

-1

. No sharp peak emission of Eu

2+

ion was observed in systems

AR

’F4 (

A

=Na

K;

R

'=Lanthanoid ions except La

Gd and Lu).The data on ESC

A

and magnetic susceptibility show that divalence europium is stable in

AR

F

4

:Eu

2+

synthesized in the stream of high purity argon.