Table 2
Crystal structures of Potassium Borates
Stoichiometry
KlBmHnO(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.
1
1
0
Potassium metaborate
R3̄ c
7.76, 110.6
n/a
1.33–1.38
[B3O6]
3−
ions [36]
R3̄ c
n/a
1.331–1.398
[37]
1
2
4
Potassium tetraborate tetrahydrate
298
P212121
12.899, 11.774, 6.859
1.447–1.511
1.312–1.401
[B4O5(OH)4]
2−
ions [38]
1
2
0
Potassium diborate
1073
6.46, 9.56,10.38,
90.7, 102.6, 101.2
[39]
973
P1̄
6.484, 9.604,10.413,
89.28, 102.75,101.25
1.435–1.508
1.357–1.381
Condensed B4O5,
B3O3
and BO3 units [40]
2
5
5
Pna21
12.566,6.671,11.587
1.454–1.496
1.346–1.412
[B
5 O
8 (OH)] unit [41]
2
5
2
443
C2/c
18.077,6.857,13.266
95.271
298
1.449–1.513
1.350–1.413
B3O3
and B4O5 units [42]
1
3
6
298
C2/c
15.540,6.821,14.273,
104.44
163
1.462–1.489
1.347–1.393
[B
3 O
3 (OH)
4 ]
−
ions [43]
1
3
2
428
P4
̸ ncc
11.3482,15.9169
1.426–1.471
1.270–1.468
[B12O16(OH)8]
4ions [44]
1
3
1
453
P21
̸ n
9.036,6.6052,15.997,
91.862
298
1.451–1.482
1.337–1.398
B
3 O
3 units [45]
1
3
0
Potassium triborate
1073
10.63, 10.64, 13.01,
90.7, 95.2, 114.2
[39]
1073
P21
̸ c
9.319, 6.648,21.094
94.38
1.455–1.492
1.332–1.406
B
3 O
3 units [46]
5
1 9
0
γ-potassium pentaborate
1073
11.59, 17.80, 12.99,
95.8
[39]
Pentapotassium
enneakaidekaborate
1023
C2/c
17.888,11.479,12.973,
95.52
295
1.459–1.494
1.336–1.404
B5O6, B3O3, BO3,
and BO4 groups [47]
1
5
8
Potassium pentaborate
hydrate
Aea2
11.08,11.11,8.97
1.53
1.28–1.42
[48]
Aea2
11.065, 11.171, 9.054
[49]
(continued)
A Crystallographic Review of Alkali Borate Salts …
113