Table 1
Crystal structures of sodium borates
Stoichiometry
Na
l B
m H
n O
(l+3m+n)/
2
Name
Synth T(K)
Space group
Unit cell
(Å or deg.)
X-ray T(K)
B-O (Å)
ranges
Comments
l
m
n
Tetrahedral
Trigonal
Refs.
3
1
0
748
P21
̸ c
5.687,7.530,9.993
127.15
n/a
1.377–1.409
[BO
3 ]
3−
ions [2]
2
1
1
523
Pnma
8.627,3.512,9.863
n/a
1.351–1.439
[BO2(OH)]
2−
ions [3]
1
1
8
298
P1̄
6.126,8.1890,6.068
67.92,110.58,101.85
1.474–1.479
n/a
[B(OH)
4 ]
−
ions [4]
1
1
4
293
P21
̸ a
5.886,10.566,6.146
111.60
1.463–1.483
n/a
[B(OH)4]
−
ions [5]
3
3
4
383
Cc
12.8274,7.7276,6.9690
98.161
293
1.445–1.497
1.340–1.399
[B
3 O
4 (OH)
4 ]
3−
ions [6]
3
3
2
423
Pnma
8.923,7.152,9.548
1.464–1.488
1.318–1.432
[B
3 O
5 (OH)
2 ]
3−
ions [7]
1
1
0
Sodium metaborate
R3̄ c
11.925,6.439 (hex)
7.212, 111.54 (rhomb)
n/a
1.280,1.433
[B
3 O
6 ]
3ions [8]
2
3
1
523
P21
̸ c
8.709,11.917,9.468
96.02
1.443–1.512
1.334–1.396
[B12O20(OH)4]
8−
ion [9]
3
5
4
423
Pbca
8.804,18.371,10.924
1.425–1.531
1.351–1.398
Layers of B
5 O
6
polyhedra [10]
3
5
2
523
Pca21
11.2373,6.0441,11.1336
291
1.440–1.510
1.367–1.377
Layers of B5O6
polyhedra [11]
1
2
10
Borax (sodium
tetraborate decahydrate)
C2/c
11.89, 10.74, 12.19
[12]
C2/c
11.858,10.674,12.197
106.68
298
1.46–1.54
1.32–1.40
Chains of [B4O5(OH)4]
2−
ions [13]
298
C2/c
11.885,10.654,12.206
297
1.464–1.500
1.363–1.374
Neutron diffraction [14]
(continued)
A Crystallographic Review of Alkali Borate Salts …
109
Crystal structures of sodium borates
Stoichiometry
Na
l B
m H
n O
(l+3m+n)/
2
Name
Synth T(K)
Space group
Unit cell
(Å or deg.)
X-ray T(K)
B-O (Å)
ranges
Comments
l
m
n
Tetrahedral
Trigonal
Refs.
3
1
0
748
P21
̸ c
5.687,7.530,9.993
127.15
n/a
1.377–1.409
[BO
3 ]
3−
ions [2]
2
1
1
523
Pnma
8.627,3.512,9.863
n/a
1.351–1.439
[BO2(OH)]
2−
ions [3]
1
1
8
298
P1̄
6.126,8.1890,6.068
67.92,110.58,101.85
1.474–1.479
n/a
[B(OH)
4 ]
−
ions [4]
1
1
4
293
P21
̸ a
5.886,10.566,6.146
111.60
1.463–1.483
n/a
[B(OH)4]
−
ions [5]
3
3
4
383
Cc
12.8274,7.7276,6.9690
98.161
293
1.445–1.497
1.340–1.399
[B
3 O
4 (OH)
4 ]
3−
ions [6]
3
3
2
423
Pnma
8.923,7.152,9.548
1.464–1.488
1.318–1.432
[B
3 O
5 (OH)
2 ]
3−
ions [7]
1
1
0
Sodium metaborate
R3̄ c
11.925,6.439 (hex)
7.212, 111.54 (rhomb)
n/a
1.280,1.433
[B
3 O
6 ]
3ions [8]
2
3
1
523
P21
̸ c
8.709,11.917,9.468
96.02
1.443–1.512
1.334–1.396
[B12O20(OH)4]
8−
ion [9]
3
5
4
423
Pbca
8.804,18.371,10.924
1.425–1.531
1.351–1.398
Layers of B
5 O
6
polyhedra [10]
3
5
2
523
Pca21
11.2373,6.0441,11.1336
291
1.440–1.510
1.367–1.377
Layers of B5O6
polyhedra [11]
1
2
10
Borax (sodium
tetraborate decahydrate)
C2/c
11.89, 10.74, 12.19
[12]
C2/c
11.858,10.674,12.197
106.68
298
1.46–1.54
1.32–1.40
Chains of [B4O5(OH)4]
2−
ions [13]
298
C2/c
11.885,10.654,12.206
297
1.464–1.500
1.363–1.374
Neutron diffraction [14]
(continued)
A Crystallographic Review of Alkali Borate Salts …
109