Crystal structures of the new borate fluorides BaMBO3F2 (M = Ga, Al)

Two new berate fluorides, BaMBO3F2 (M = Ga, Al), have been synthesized by h ydrothermal and solid-state reactions, The structure of BaGaBO3F2 has been determined by single-crystal X-ray diffraction (P6(3)/m, a = 4.907(2) Angst rom, c = 9.620(5) Angstrom, Z = 2, wR(F-2)= 0.039 for 334 unique reflection s), BaAlBO3F2 has been confirmed to be isostructural by Rietveld refinement of powder X-ray data (a = 4.882(1) Angstrom, c = 9.398(1) Angstrom, Z = 2, R-wp = 0.222, chi (2) = 2.59), The BaMBO3F2 structure-type is built of (00 1) layers of corner-sharing MO3F2 triangular bipyramids and BO3 triangles, with the Ba atoms filling 12-coordinated interlayer sites. (C) 2000 Academi c press.