Developments in Ceramic Materials Research

Optical Fluoride and Oxysulfide Ceramics: Preparation and Characterization 77
Energy levels, cm -1
18700
18650
18600
18550
18500
18450
16950
16800
16650
16500
11200
11160
11120
11080
1950
1920
1890
300
250
200
150
100
50
0
18598
18498
16988
16646 1
11189
11109
1937
1916
1889
257
238
44
19
0
4
2
1
2
1
3
2
1
5
4
3
2
1
4 G7/2
2 G7/2
4 G5/2
Figure 22. Identified crystal-field (Stark) levels diagram of the 4 I 9/2, 4 I 11/2, 4 F 3/2, 4 G 5/2, 2 G 7/2 and 4 G 7/2
manifolds of the Nd 3+ ion in the Gd 2O 2S:Nd 3+ (0.1 wt%) oxysulfide optical ceramics.
The notations near the spectral lines denote the transitions between the crystal-field (CF)
levels of corresponding manifolds. The primed numbers denote the CF levels of the excited
manifold and those without prime — the CF levels of the ground manifold. Counting is from
bottom to top. Corresponding fluorescence spectrum at the 4 F3/2→ 4 I9/2 transition (Figure 21b)
allows to determine the CF (Stark) splitting of the 4 I9/2 and 4 F3/2 manifolds (Figure 22).
Absorption spectra of the 4 I9/2→ 4 G7/2 and 4 I9/2→ 2 G7/2; 4 G5/2 transitions at 77 and 300 K
(Figure 23) allow to separate the 2 G7/2 and 4 G5/2 manifolds. A spin-forbidden 4 I9/2→ 2 G7/2
transition has lower intensity than the spin-allowed 4 I9/2→ 4 G5/2 transition and takes up higher
position on the energy scale. Thus the minimal energy gap ΔEmin=1517 cm −1 is in between the
lowest CF level of the 4 G7/2 manifold and the upper CF level of the 2 G7/2 manifold. The
absorption spectral lines measured in the Gd2O2S:Nd 3+ (0.1%) optical ceramics are well
pronounced as opposed to those in the La2O2S:Nd 3+ (1%) optical ceramics (not presented).
The later may be concerned with the inhomogeneous broadening of the CF transition spectral
lines at larger concentration of Nd 3+ in the La2O2S ceramics.
4 F3/2
4 I11/2
4 I9/2