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Two Novel Acentric Borate Fluorides: M3B6O11F2 (M = Sr, Ba)

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journal contribution
posted on 02.04.2012, 00:00 by Colin D. McMillen, Jared T. Stritzinger, Joseph W. Kolis
Two novel, noncentrosymmetric borate fluorides, Sr3B6O11F2 and Ba3B6O11F2, have been synthesized hydrothermally and their structures determined. The compounds are isostructural, crystallizing in space group P21, having lattice parameters of a = 6.4093 (13) Å, b = 8.2898 (17) Å, c = 9.3656 (19) Å, and β = 101.51 (3)° for Sr3B6O11F2 and a = 6.5572 (13) Å, b = 8.5107 (17) Å, c = 9.6726 (19) Å, and β = 101.21 (3)° for Ba3B6O11F2. The structure consists of a complex triple-ring borate framework having aligned triangular [BO3] groups that impart polarity. Fluorine atoms are bound only to the alkaline-earth metals and are not part of the borate framework, resulting in a vastly different structure from those of the hydrated borates Sr3B6O11(OH)2 and Ba3B6O11(OH)2 with similar formulas. The title compounds are transparent to nearly 200 nm, making them potentially useful for deep-ultraviolet nonlinear-optical applications.