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Ba4YZr3F23 and Ba4LnZr3F23: a new noncentrosymmetric potential host structure type for optical devices
Jean Paul Laval1, Abdelkrim Taoudi1
1Institut de Recherche sur les Céramiques, IRCER-UMR-CNRS 7315, Université de Limoges, Faculté des Sciences, 12 rue Atlantis, 87068 Limoges, France.
Abstract:
The first ternary BaF2-Ln(Y)F3-ZrF4 phases crystallizing near the composition range of fluoride glasses, namely Ba4YZr3F23 (barium yttrium fluoridozirconate) and isotypic Ba4LnZr3F23 (Ln = Yb, Er and Nd), have been synthesized. The crystal structure of Ba4YZr3F23 cannot be correctly determined in the centrosymmetric space group Pnma (R1 = 0.09); it is preferably described in the noncentrosymmetric space group Pn21a (R1 = 0.028). All cations are located at y = 0.25-0.29 and 0.75-0.79. This new structure type is formed by infinite {[YZr3F23]8-}n columns associating, along [001], YF9 tricapped trigonal prisms, ZrF8 dodecahedra and ZrF7 polyhedra. These columns are interconnected via BaF10+1 and BaF12 irregular polyhedra.
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