Geoscience Reference
In-Depth Information
Table 7.21 Physicochemical Properties of Some Rare Earth Germantes
[44]
d
(g/ cm
3
)
Melting temperature
T
(
C)
Compound
Reference Indices
La
2
GeO
5
5.97
1800
1.940
Nd
2
GeO
5
6.55
1820
6
25
1.948
Gd
2
GeO
5
7.07
1.880
1.941
Y
2
GeO
5
4.83
1975
6
15
1.848
Er
2
GeO
5
7.28
2000
6
50
1.904
1720
a
La
4
GeO
8
6.30
1.973
1650
a
Gd
4
GeO
8
7.77
1.975
Y
4
GeO
8
5.10
2000
1.887
1600
b
Er
4
Ge
8
8.02
1.93
La
4.67
[GeO
4
]
3
5.89
1770
1.930
1680
a
La
2
Ge
2
O
7
5.67
1.900
1820
6
25
a
Nd
2
Ge
2
O
7
6.16
Gd
2
Ge
2
O
7
6.70
1770
1.922
Y
2
Ge
2
O
7
4.69
1800
6
25
1.840
α
-Er
2
Ge
2
O
7
6.99
1875
6
50
1.890
β
-Er
2
Ge
2
O
7
1.938
Sc
2
Ge
2
O
7
4.46
1850
1.847
La
2
Ge
3
O
9
5.94
1300
1.995
a
With decomposition.
b
With decomposition in solid phase.
The Sm- and La-bearing germanates are diamagnetic. The magnetic transition tem-
peratures for oxyortho- and diorthogermanates are as follows
[219]
:
Tb
2
Ge
2
O
7
5
2
:
05
0
:
05 K
6
Dy
2
Ge
2
O
7
5
2
:
15
0
:
05 K
6
Ho
2
Ge
2
O
7
5
1
:
45
0
:
05 K
6
Er
2
Ge
2
O
7
5
1
:
15
0
:
05 K
6
Dy
2
GeO
5
5
2
:
50
0
:
10 K
6
Er
2
GeO
5
5
1
:
25
6
0
:
10 K
Most of the works on the investigations of physical properties of rare earth ger-
manates deal with the luminescence properties. Their emission and absorption
spectral characteristics have been studied in great detail.
Figure 7.53
shows the
luminescence spectra of NaEuGeO
4
and NaTbGeO
4
[220]
.
Figure 7.54
shows the
excitation spectrum of NaGd
3
[GeO
4
]
2
(OH)
2
:Tb
3
1
(2.5%)
[221]
.
