Na

5

Eu(MoO

4

)

4

and NaEu(MoO

4

)

2

are stoichiorr.etric host luminescent materials having high concentration of luminescent Eu

3+

ions and no noticeable concentration quenching. Raman spectra of these two materials have been studied. The symmetry species of the lattice vibration modes of Na

5

Eu(MoO

4

)

4

have been analysed by means of the group theory.The structures of both materials belong to tetragonal

I

4

I

/a (C

4h

6

) space group. For Na

5

Eu(MoO

4

)

4

the free ion symmetries of (MoO

4

)

2-

Eu

3+

and Na

1+

correlate with factor group C

4h

through their site groups. A primitive cell includes two Na

5

Eu(MoO

4

)

4

molecules. It mears that 8 (MoO

4

)

4

2-

10 Na

1+

and 2 Eu

3+

are included in the cell. So the lattice vibration of Na

5

Eu(MoO

4

)

4

in the cell can be classified into 72 internal modes and 84 external modes. For crystal factor group C

4h

the

A

g

B

g

and

E

g

modes are Raman active and

A

u

and

E

u

modes are infrared active.