A Note on the Structure of Barium Tetraborate.

Dehydration Process of TlB5O6(OH)4·2H2O and Crystal Structure of TlB5O8

“…The crystal system is orthorhombic, and the unit cell parameters near to those previously published (13), refined from 25 reflections, are a"7.557(3) A s , b"11.925(6) A s , c"14.734 (19) A s ; »" 1328(2) A s ; M"386,417 g mol\; D "3.6 g cm\; D " 3.865 g cm\ ; Z"8; F(000)"1360. Systematic extinctions of l"2n#1 reflections for (0kl) and (h0l) and h"2n#1 for (hk0) have confirmed the Pbca space group previously proposed (13) by anology with isotypic -KB O (16,17).…”

“…In this paper, this latter route was studied, and the structure of TlB O was determined. A previous study (15) had shown that TlB O was isotypic of the low-temperature modification of potassium pentaborate, -KB O ; the structure of this compound had been remarkably established by Krogh-Moe¨ (16,17) using intensity data obtained from Weissenberg exposures until R"11.1%. It was necessary to obtain better intensity data for TlB O to establish more precisely the borate polyanion geometry existing in this compound and compare it with the structure of its hydrated precursor, TlB O (OH) )2H O (14).…”

On the crystal structure of barium tetraborate, BaO.4B2O3

“…Levin & McMurdie stated that this phase 'appears as irregular grains, many of which are striated as in polysynthetic twinning and is uniaxial negative or biaxial negative with a small optic axial angle'. Krogh-Moe (1960) determined the following unit-cell dimensions from single-crystal Weissenberg photographs: a=8.56, b=2x 8.69 (very weak doubling of b axis), c= 13-20/~. The Weissenberg photographs showed the phase to be probably orthorhombic, but with a pronounced pseudotetragonal symmetry (in agreement with the optical properties).…”

HP‐KB3O5 Highlights the Structural Diversity of Borates: Corner‐Sharing BO3/BO4 Groups in Combination with Edge‐Sharing BO4 Tetrahedra

“…With HP-KB 3 O 5 (HP = high pressure), we synthesized a new borate, in which the two well-known fundamental structural motifs, alias BO 3 and BO 4 groups, and all noted conjunctions, namely corner-sharing of BO 3 /BO 4 groups and corner-as well as edge-sharing of BO 4 tetrahedra, are discovered in one crystal structure for the first time. This occurred in the scope of pressure-induced crystallization experiments on glass forming alkali borates, whilst investigating the ternary system K-B-O, where six different crystal structures are known: K 5 B 19 O 31 , [15] KB 5 O 8 , [16,17] [20,21] and KB 3 O 5 . [22,23] The latter (ambient-pressure modification) is built up from rigid triborate rings consisting of two corner-sharing BO 3 triangles and a cornersharing BO 4 tetrahedron.…”