Crystal structure of Ba₈[Al₃O₁₀][AlO₄], a novel mixed-anion Ba aluminate related to kilchoanite

Abstract

Crystal growth experiments in the system BaO Al 2 O 3 yielded single crystals of a new Ba oxoaluminate with composition Ba 4 Al 2 O 7 . The title compound is orthorhombic, with cell parameters a = 11.3126(5), b = 11.7045(9), c = 27.1850(14) A Ê , space group Cmca. The structure was solved by direct methods followed by difference Fourier synthesis from X-ray single crystal diffraction data (R1 = 0.048 for 1213 independent observed reflections and 135 parameters). The main building units of tetrabarium aluminate are Al 3 O 10 trimers and isolated AlO 4 tetrahedra. Seven crystallographically different Ba sites crosslink between the tetrahedral groups and are co-ordinated by six to nine oxygen ligands. The structure is closely related to the mineral kilchoanite (Ca 6 [SiO 4 ][Si 3 O 10 ]) and the first representative of an unbranched oligo-aluminate with triple tetrahedra.

K2ScSn(AsO4)3: an arsenate-containing langbeinite

“…The mean KÁ Á ÁO separations and their estimated errors (Taylor & Kennard, 1983) for K1 and K2 are 3.03 (4) Å and 3.16 (15) Å , respectively. Their bond valence sums (BVSs), calculated by the Brown & Altermatt (1985) formalism, are 0.79 and 0.62, respectively (expected 1.00); thus, they are both significantly 'underbonded' (Kahlenberg, 2001)…”

Synthesis and characterization of a novel alkali mixed magnesium-aluminum phosphate with a layered structure–KMgAl(PO4)2

“…The MO4 tetrahedrons have three equal M−O distances of 1.808(4) Å and one of 1.795(5) Å. For these tetrahedrons, the M-O bonds are much longer than those (Al-O) observed typically for AlO4 (1.71 Å) [33,34] and much shorter than those (Mg-O) for MgO4 (1.96 Å) [35,36]. This results in abnormal value of the calculated distribution charge, +2.5 for Mg and Al cations.…”

Super-tetragonal Sr 4 Al 2 O 7 as a sacrificial layer for high-integrity freestanding oxide membranes

“…To the best of our knowledge, none of the reported strontium aluminates can match the STEM and XRD results. We searched numerous possible structure candidates and eventually found that the SAO T could share an atomic structure similar to that of the orthorhombic Ba 4 Al 2 O 7 compound ( 42 ). DFT-level structure relaxations further confirm that the orthorhombic Sr 4 Al 2 O 7 unit cell is thermodynamically stable, with simulated lattice constants a SAO-T = 10.798 Å, b SAO-T = 11.238 Å, and c SAO-T = 25.732 Å [see section 2 of ( 40 )].…”

“…As depicted in fig. S34, the Al-O networks in SAO T comprise discrete AlO 4 5− and Al 3 O 10 11− groups, which hydrolyze in water more readily than the Al 6 O 18 18− rings in SAO C ( 14 , 42 , 48 ). Despite such a high water solubility, the SAO T film exhibits exceptional stability against ambient moisture over 40 days when incorporating an ultrathin STO protective layer (fig.…”