For the excellent properties such as high quantum efficiency

long persistence of phosphorescence which may reach 16h

no radiation

and good stableness

SrAl

2

O

4

:Eu

2+

Dy

3+

phosphors have indicated their good practical prospects.Preparation of the phosphors has been conducted from the beginning of this decade.The synthesis of this kind of phosphor generally requires high temperature (i.e.

1300～1500℃) by solid state reaction.The matrix composition

structure and luminescent properties of the phosphors could be affected under different synthesizing conditions

such as calcining temperature

soaking time etc.However

little attention is paid to their synthesis conditions

structures and properties.The present work was motivated by the possibility of acquiring optimal calcining technology parameters for the applications of the long-lasting phosphors.In this paper

the SrAl

2

O

4

:Eu

2+

Dy

3+

phosphors were synthesized by high temperature solid state reaction process at weak reductive atmosphere (4%H

2

～96%N

2

).The preparation conditions and their effect on the luminescent properties of SrAl

2

O

4

:Eu

2+

Dy

3+

phosphors have been investigated.Based on the XRD peaks

the powder phosphors were identified as SrAl

2

O

4

phase

which is monoclinic (

a

=8.4424Å

b

=8.822Å

c

=5.1607Å

β

=93.415°).The results proved that the phosphors synthesized at different temperature in this work are all α phase

and the little amount of doped rare earth ions (Eu

2+

:0.2mol%

Dy

3+

:0.2mol%) have nearly no effect on the SrAl

2

O

4

matrix phase composition.The typical SEM micrographs of the sample synthesized at 1500℃ (Sample A) and the sample synthesized at 1300℃ (Sample B) implied that the clusters are spherical

porous and multi crystalline.The average grain sizes of Sample A and Sample B are about 14.4μm and 4.8μm respectively

calculated on the ball like particles.The excitation and emission spectra of the phosphors were measured and analyzed.At room temperature

both samples exhibit broadband excitation and emission peaks in the photoluminescence spectra.Three excitation peaks were observed in Sample A

since two shoulders at 327nm and 374nm in addition to the maximum at 430nm.The emission peak was at 518nm with a bandwidth of 70nm.Compared with Sample A

in Sample B

the excitation and emission spectra exhibit similar shapes

however

both of them shift to the blue side in the photoluminescence spectra.The excitation peaks were at 317

362 and 425nm; the emission peak was at 515nm with a band width of 68nm.The results indicate that the main peaks of Sample B

which has a smaller grain size than Sample A

intend to shift to shorter wavelength.The results indicated that the luminescence of these phosphors is due to 4f

6

5d→4f

7

transition of Eu

2+

.The observed discrepancy in shifting of main peaks may be attributed to the difference in the crystal field strength that Eu

2+

experienced and inherited from different synthesis routes.