Na

5

Eu(MoO

4

)

4

like Na

6

Eu(MoO

4

)

4

is a kind of good stoichiometric host luminescent material having high concentration of Eu

3+

and no concentration quenching effect.The power crystals Na

5

Eu(MoO

4

)

4

and NaEu(MoO

4

)

2

have been synthesized. According to differential thermal and X-ray diffraction analyses

a phase diagram of the system Na

2

MoO

4

-Eu

2

(MoO

4

)

3

has been determined.The methods for synthesizing pure Na

5

Eu(MoO

4

)

4

and NaEu(MoO

4

)

2

have been determined. It shows that Na

5

Eu(MoO

4

)

4

will not be dissociated to NaEu(MoO

4

)

2

when Na

2

MoO

4

is excessive and the ratio of molal concentration of Na

2

MoO

4

to Eu

2

O

3

is more than about 8:1 at sintering temperature lower than 700℃.Both of Na

5

Eu(MoO

4

)

4

and NaEu(MoO

4

)

2

crystallize in the schee-lite structure type and belong to the tetragonal crystal system. The X-ray powder diffraction pattern of NaEu(MoO

4

)

2

was indexed in a"pure" scheelite cell with parameters

α

=0.5236nm and

c

=1.1439nm (d

caic

=5.24g/cm

3

z

=2

space group

I

4

1

/α). Thus

the entire series of NaEu (MoO

4

)

2

compounds is isostructural. But all of the X-ray powder diffraction lines of Na

5

Eu(MoO

4

)

4

can only be indexed in the enlarged scheelite cell with parameters

α

=1.1439nm and

c

=1.1486nm (

d

caic

=4.01g/cm

3

z

=4

space group

I

4

1

/α). In this paper

the cation distribution in the unit cell of both compounds is discussed.The purity of Na

5

Eu(MoO

4

)

4

and NaEu(MoO

4

)

2

samples can be determined sensitively by the intensity analysis of main peaks of the two compounds by X-ray diffraction mathod.The excitation and emission spectra of both compounds have been determined.