Trivalent terbium activated garnet-type cadium aluminium germanate Cd

3

Al

2

Ge

3

O

12

:Tb phosphor have been synthesized. The diffused reflecion spectra

excitation spectra and emission spectra for the host lattice and Tb

3+

-activated phosphor were measured at room temperature. It is observed that the undoped host lattice and Cd

3

Al

2

Ge

3

O

12

:Tb phosphor exhibit both bright and long phosphorescence after UV-excited light is turned off. Phosphorescence of the host lattice shows blue light

but that of Tb

3+

-activated phosphor shows the characteristic green-yellow emission of Tb

3+

ion. The decay of both phosphorescences agree with B=At

-a

. The phosphorescence phenomenon is the result of energy transfer from the host lattice to Tb

3+

ion.