The diffusive reflection spectra

the excitation and emission spectra of Cd

3

Al

2

Ge

3

O

12

host (abbr.:CAGG)and Cd

3

Al

2

Ge

3

O

12

:Mn

2+

(abbr.:CAGG:Mn

2+

)garnet phosphors at RT have been systematically investigated. The diffusive reflection spectrum (Fig.1) of the CAGG:Mn

2+

shows a strong absorption band at about 250urn which coincides with that of the CAGG host and three weak absorption bands at 360urn

397urn and 414um from

4

T

2

4

A

1

and

4

E levels of Mn

2+

respectively. As shown in Fig. 2 the excitation spectrum of Cd

3

Al

2

Ge

3

O

12

:Mn

2+

is the same as that of the CAGG host.CAGG host Under excitation of 254um at RT shows a blue emission band extending from 350um to 560nm with a peak at about 450um. Photoluminescence spectrum ofCd

3

Al

2

Ge

3

O

12

:Mn

2+

garnet consists of two emission bands (to see Fig. 3). The emission band in blue region is from CAGG host and the strong emission band in yellow region is from Mn

2+

emission

whose peak is at 570nm resulting from transition of

4

T

1

(G) to

5

A

1

level of the Mn

2+

ion. With increasing the concentration of the Mn

2+

ion

the emission intensity in the blue region from CAGG host decreases and then emission intensity of Mn

2+

ion increases. The emission of CAGG host is completely quenched when the concentration of Mn

2+

ion reaches 0.2%.We consider that the nonradiative resonance energy transfer from CAGG host to Mn

2+

ion occurs in the system of Cd

3

Al

2

Ge

3

O

12

:Mn

2+

garnet phosphors. The spectroscopic properties of the yellow band of the Mn

2+

ion in CAGG garnets have been disc ussed.