Geoscience Reference
In-Depth Information
Table 7.10 Anionic Structural Motif in Rare Earth and Alkali Rare Earth Silicates
[52]
Radical Form
Representative
Structure Type
Rare Earth
Polyhedra
Co. No. of
Rare Earth
Cations
Orthotetrahedra
[SiO
4
]
Gd
2
[SiO
4
]O
Framework
7, 9
Yb
2
[SiO
4
]O
Framework
6, 7
Ge
4.66
[SiO
4
]
3
O
Framework
7, 9
Eu
2
[SiO
4
]
Framework
8, 10
NaNd[SiO
4
]
Column
9
NaSm[SiO
4
]
4-Membered ring
6
NaY[SiO
4
]
Discrete polyhedra
6
4{NaYSiO
4
}NaF
4-Membered ring
6
Na
2
La[SiO
4
](OH)
Framework
8
KNd
9
[SiO
4
]
6
O
2
Framework
7, 9
Diortho-[Si
2
O
7
]
La
2
[Si
2
O
7
]
Framework
7, 8, 9
Yb
2
[Si
2
O
7
]
6-Membered ring
6
Er
2
[Si
2
O
7
]
Layer
6
Gd
2
[Si
2
O
7
]
Framework
7
Eu
2
[Si
2
O
7
]
Framework
8
Nd
2
[Si
2
O
7
]
Framework
8
Yb
2
[Si
2
O
7
]
Framework
7
(Y,Th)
2
[Si
2
O
7
]
Layer
6
Na
3
Sc [Si
2
O
7
]
Discrete polyhedra
6
Na
6
YSc[Si
2
O
7
]
2
Discrete polyhedra
6
Na
3
Y [Si
2
O
7
]
Discrete polyhedra
6
K
3
Eu [Si
2
O
7
]
Discrete polyhedra
6
Triortho-[Si
3
O
10
]
Y
3
[Si
3
O
10
](OH)
Layer
7, 8
K
3
Y[Si
3
O
8
](OH)
2
Discrete polyhedra
6
Tetraortho-[Si
4
O
13
]
Na
4
Sc
2
[Si
4
O
13
]
Bicapped polyhedra
6
Mixed ortho- and
triortho-[SiO
4
]
and [Si
3
O
10
]
Ho
4
[Si
3
O
10
][SiO
4
]
Ribbon
8
Ring: [Si
4
O
12
]
Four
K
4
Sc
2
[Si
4
O
12
](OH)
2
Column
6
Twelve [Si
12
O
36
]
Na
5
Lu[Si
4
O
12
]
Discrete polyhedra
Spiral chain
[Si
24
O
72
]
Na
3
Y [Si
3
O
9
]
Discrete polyhedra
6
Layers: from 6,8,
12-rings [Si
3
O
8
]
K
8
Yb
3
[Si
6
O
16
]
2
(OH)
Discrete and
twinned polyhedra
6
From 4,5,6,8-rings
NaNd[Si
6
O
13
]
(OH)
2
; nH
2
O
Discrete polyhedra
7
From 4,6,8-rings
[Si
2
O
5
]
Na
2
Ce[Si
6
O
14
]
(OH)
nH
2
O
Discrete polyhedra
7
K
3
Nd[Si
6
O
15
]
Discrete polyhedra
6
Three-storeyed
column [Si
3
O
7
]
NaNd[Si
6
O
14
]
Column
6
Framework [Si
2
O
5
]
K
2
Ce[Si
6
O
15
]
Discrete polyhedra
6
