Color plasma display panel(PDP)is the most promising flat display for the large area display.Phosphors used in PDP are excited with vacuum-ultraviolet radiation.Naturally

the phosphors are required to have a good quantum efficiency in the region below 200um.Some silicates have stronger absorption in the VUV region.Therefore

it is important to investigate silicates.On the other hand

oxyorthosilicates have good thermal stability and chemistry stability

and also are good host for luminescent materials under UV excitation.However

optical properties of Y

2-x

Gd

x

SiO

5

: Eu in the VUV range have not been reported up to now.Y

1.95-x

Gd

x

SiO

5

:Eu

0.05

were prepared at 1200℃ for two hours with NH4F flux by solid-state reaction.Y

1.95-x

Gd

x

SiO

5

:Eu

0.05

are polymorphic and crytallizable in the monoclinic X

2

type with space group B2/b.The excitation spectra of Y

1.95-x

Gd

x

SiO

5

:Eu

0.05

monitored at 612um consists of a broad band at 220-300um corresponding to the charge transfer band of Eu

and a number of lines which could be assigned to the f-f transition of Eu

3+

for 300-540nm

and the strongest excited peak lies at 396nm.The emission spectrum of Y

1.95-x

Gd

x

SiO

5

:Eu

0.05

phosphors excited under 396mn irradiation consists of four groups of emission lines in the rang of 560-720nm.The maximum emission peak is located at 612urn.One luminescence line at 580nm

three lines at 590-596nm

five lines at 610-630nm and three lines at 685-705nm are assigned to the transitions 5D07F0

5DO7F1

5DO7F2

5D07F4

respectively.When a x(

x

= 0.2

0.4

0.6)mol faction of gadolinium is incorporated into the host lattice

the location of absorption peaks of Eu

3+

shown in VU-vis excitation specturm of Y1.95-xGdxSiO5: Eu0.05 are not changed

but the relative intensities of these peaks decrease with increasing Gd

3+

concentration.In the vacuum-ultraviolet region

the new absorption peak near 192nm appears.The intensity of the new peak assigned to the absorption of 6Gj configuration of Gd

3+

increases with increasing Gd

3+

concentration until 0.4 mol%

and then

the intensity decreases.The intensity of the host absorption band of the phosphors at 150-185nm is enhanced while the intensity of the charge transfer band of Eu decreases with increasing Gd

3+

concentration.Generally speaking

when a x mol fraction of gadolinium is incorporated into the host lattice

the luminescent intensity in vacuum-ultraviolet region increases in spite of the decreasing in VU-vis region.That is in favor of enhanching the luminescent intensity of phosphors used in PDP.