Nd₄Ti₉O₂₄: Präparation und Struktur

Abstract

Pulverförmige Präparate der Verbindung Nd4Ti9O24 ließen sich durch Erhitzen (an Luft; Pt‐Tiegel) eines Gemenges Nd2O3/TiO2 (1 : 4,5) phasenrein darstellen (1 330°C, 2× 1 d). Einkristalle wurden durch chemischen Transport (T2 → T1; T2 = 1000 °C, T1 = 900°C, 14d) mit Nd4Ti9O24 als Startbodenkörper bei T2 sowie mit Chlor (p(Cl2 298 K) = 1 atm) als Transportmittel erhalten. Nd4Ti9O24 kristallisiert orthorhombisch: RG Fddd (No. 70) mit den Gitterkonstanten a = 13,9926(11) Å,b = 35,2844(21) Å, c = 14,4676(17) Å mit Z = 16. Die Struktur wurde bis zu R = 4,0% bzw. Rw = 3,7% verfeinert. Der Aufbau kann durch ein kompliziertes dreidimensionales Gerüst aus TiO6− und Nd(2)O6−Oktaedern beschrieben werden, in dessen Lücken Nd(1) und Nd(3) mit CN = 8 lokalisiert sind. Die Koordination der Metallteilchen 1äßt sich durch TiO6− Oktaeder, NdO8 quadratische Antiprismen (verzerrt) und durch NdO6−Oktaeder beschreiben.

Octahedral oxide glass network in ambient pressure neodymium titanate

“…Thus, the HEXRD value is used for all analyses here. For comparison, the density of the compositionally closest crystalline phase, Nd 4 Ti 9 O 24 (18.2 mol.% Nd 2 O 3 ), is 5.178 g cm −3 19 . The most pertinent glass estimates from literature are for the compositional analogue 83TiO 2 -17La 2 O 3 , for which Alderman et al .…”

“…Mean bond distances in EPSR were calculated from the running atomic coordination, with cutoff distances of 2.6 Å for Ti-O and 3.25 Å for Nd-O. For comparison, the Ti-O and Nd-O bond distances were analyzed for crystalline Nd 4 Ti 9 O 24 19 using GSAS-II 39 and are compared in Table 1 . For the glass, = 1.984(11) Å, in close agreement with the crystalline Nd 4 Ti 9 O 24 average (1.974 Å).…”

Phase relations, crystal chemistry, and dielectric properties in sections of the La2O3–CaO–MgO–TiO2 system

“…The structure of La 2 TiO 5 features Ti 4+ in five-fold trigonal bypyramidal coordination [13], whereas La 2 Ti 2 O 7 adopts a perovskite-slab type structure [14,15]. La 4 Ti 9 O 24 [16] was confirmed to be isostructural with Nd 4 Ti 9 O 24 [17,18], which exhibits an orthorhombic framework-type structure featuring pairs of edge-sharing [TiO 6 ] octahedra with six-and eight-fold coordinated Nd 3+ . A fifth compound, cation-deficient perovskite-related ''La 2/3 TiO 3 '' [19], does not occur as such in the La 2 O 3 -TiO 2 system, but is stabilized by small amounts of Ti 3+ , by partial filling of the A-sites with mono-or divalent cations [12], or by partial substitution of Ti 4+ with trivalent cations [3,20].…”

New Results of Chemical Transport as a Method for the Preparation and Thermochemical Investigation of Solids

“…[173] The crystallization of monoclinic Nd 2 Ti 4 O 11 in a short-path transport experiment [174] is worth mentioning as is that of Nd 4 Ti 9 O 24 ( Figure 5 o), which could be transported in a temperature gradient (1000 3 900 8C) with chlorine. [175] Recently the short-path transport of Pr 4 Ti 9 O 24 succeeded, [172] whereas transport reactions with the compounds La 4 Ti 9 O 24 and Ce 4 Ti 9 O 24 , which are also isotypic to Nd 4 Ti 9 O 24 , could not be realized. [162] The new silicate-titanate Ce 2 Ti 2 SiO 9 was produced in the sink (1050 3 900 8C) when the binary oxides were used as the reactants and SiO 2 was present in excess with NH 4 Cl.…”