Crystal/Defect Structures and Phase Stability in Ba Hexaaluminates

Synthesis, crystal structure, spectrum properties, and electronic structure of a new barium aluminoborate, Ba8[(Al6IV)(Al2IV)(Al2V)B12IIIO41]∞

“…2 and Table 2, the asymmetric unit of Table 4). These geometric parameters are comparable to those observed in the structures of BaAl 2 B 2 O 7 [5] and SrO(Al 2 O 3 ) 6 [22], where AlO 4 and AlO 5 groups were also observed, respectively. The calculated BVS values are 2.70-2.86 for the Al atoms, supporting the choice of four-or five-fold coordination to describe the Al environment.…”

“…The calculated BVS values are 2.70-2.86 for the Al atoms, supporting the choice of four-or five-fold coordination to describe the Al environment. Note that tetrahedral and octahedral coordination geometries are preferred by Al atoms, as found in a number of compounds, e.g., BaAl 2 B 2 O 7 [5], K 3 AlB 8 O 15 [23], TmAl 3 (BO 3 ) 4 [24], and BiCd 3 (AlO) 3 (BO 3 ) 4 [25]; AlO 5 trigonal bipyramids are rather rare, but have been previously reported in the structure of SrO(Al 2 O 3 ) 6 [22], while the unusual Latin capital H letter shaped Al 6 O 19 20− group composed of six corner-sharing AlO 4 tetrahedra, to the best of our knowledge, is present here for the first time.…”

Preparation and Crystal Structure Analysis of Magnetoplumbite-Type BaGa12O19

“…The only quantitative structural analysis reported to date for a Phase II compound in either system was the study by Iyi et al (7) on Ba(Pb) hexaaluminate (reported composition (Ba Pb ) Al O ), which is assumed to be identical to the structures of the ternary Ba hexaaluminate and Ba hexagallate Phase II compounds (7,11). To verify that the ternary structures are indeed identical to the quaternary Ba(Pb) hexaaluminate structure, however, and to elucidate any subtle differences between them, quantitative structural studies should be performed directly on the ternary systems.…”

Synthesis, Crystal Structure, and Spectrum Properties of a New Quaternary Borate NaSr7AlB18O36 with the Cyclic B18O36 18− Group, Notation of 6 × (3[2Δ + 1T])

“…Note that tetrahedral, trigonal bipyramidal, and octahedral oxygen coordination geometries have been previously reported for the Al atoms in the aluminium oxides. Among them, AlO 5 trigonal bipyramids are rare, but have been found in the structure of SrO (Al 2 O 3 ) 6 [28], while AlO 4 tetrahedra and AlO 6 octahedra are more popular: the former have been encountered in BaAl 2 B 2 O 7 [8] as well as K 3 AlB 8 O 15 [29] and the latter observed in AlBO 3 [30], TmAl 3 (BO 3 ) 4 [31], and BiCd 3 (AlO) 3 (BO 3 ) 4 [32]. The Al atom is located on a crystallographic 3 axis, thereby giving a single Al-O bond distance of 1.895(3) Å , which is comparable to those found in AlBO 3 (average Al-O = 1.923 Å ) and TmAl 3 (BO 3 ) 4 (average Al-O = 1.901 Å ), where AlO 6 groups have also been observed [30,31].…”