The crystal structure of lanthanum hexaaluminate

Defect Energetics and Nonstoichiometry in Lanthanum Magnesium Hexaaluminate

“…Our results indicate that, in the stoichiometric LMA, the ''type 1'' and ''type 2'' defect complexes, which were postulated by Iyi et al (13) to explain the nonstoichiometry in pure LHA, are not likely to be formed. In Mg-deficient (and Al-excess) nonstoichiometric LMA, however, it is suggested that the type 2 vacancy model defect complex is expected to be formed in the interspinel layers.…”

“…In order to explain the nonstoichiometry in lanthanum hexaaluminate (LHA, ideal composition LaAl O ), Iyi et al (13) proposed two types of defect models, a ''vacancy model'' and an ''interstitial oxygen model,'' based on the MP structure. They also postulated two types of defect configuration, ''type 1'' and ''type 2,'' for each model.…”

Crystal/Defect Structures and Phase Stability in Ba Hexaaluminates

“…resolution electron microscopic images they proposed a Until the early seventies, Ba hexaaluminate was assigned different structural model for Ba hexagallate of phase II the magnetoplumbite structure with stoichiometry of type, which is possibly isostructural with Ba hexaaluminate BaAl 12 O 19 , like other hexaaluminates of divalent cations, phase II. In that model, the excess barium ions are positioned midway between the spinel-block centers and alter- The simulations in this study are based on the Born dral site.…”

“…The crystal structure of phase I is well characterized in the two independent studies by van Berkel et al (8) and defined. This new lattice vector matrix can thus be expressed directly in terms of the original basis vectors and Iyi et al (9). In their proposed structural model, there are two kinds of half unit cell which contain a mirror plane the bulk lattice strains.…”

“…The crystal structure of a barium lead hexaaluminate (ideal formula PbFe 12 O 19 ). The two parent structures, ͱ-phase II, reported by Iyi et al (12), is the only one, providalumina and magnetoplumbite, are similar, characterized ing refined structural parameters.…”