Terbium activated simple phosphates of lanthanum

yttrium

and gadolinium are cathodo-

UV photo-

and roentgeno-luminophors.As regard to the double phosphates there was only one article written by D'Silva

[4]

relating to the study of roentgenoluminescent properties of the system yttrium gadolinium phosphate.In this work samples of terbium activated yttrium gadolinium phosphate system Y

1-x

Gd

x

PO

4

:Tb were prepared by solids state reaction of corresponding metal oxides and ammonium hydrophosphate in the presence of flux sodium pyrophosphate.Their luminescent properties under the excitation of cathode rays

UV light

and X-rays have been investigated. A possible mechanism of concentration quenching of activator terbium ions has been postulated.Figures 1-1

1-2

and 1-3 show the cathode-

UV photo-

and roentgeno-luminescence spectra.They all consist of a set of sharp emission lines corresponding to the

5

D

3

-

7

E

J

and

5

D

4

-

7

F

J

transitions of terbium.In

5

D

3

-

7

F

J

transitions the

5

D

3

-

7

F

6

(λ=382nm)is the strongest one.In

5

D

4

-

7

F

J

transitions the

5

D

4

-

7

F

5

(=544nm) is the strongest one.