Synthèse et structure cristalline de Rb5VONb14O38 (original) (raw)

Structure cristalline de CsCrI3

Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 1979

CsCrI 3 crystallizes in space group P63mc with a = 8. 132 (5), c = 6.946 (5) A, Z = 2. The crystal structure was refined from 217 independent reflexions by the full-matrix least-squares method to a final R index on F of 0.044 and a weighted R w index of 0.050. CsCrI 3 is isostructural with CsCrCI 3 and CsCrBr 3. These compounds do not show any evidence of a cooperative static Jahn-Teller effect.

Synthèse et structure cristalline de Na3NbO(AsO4)2

Journal of Solid State Chemistry, 1999

The compound Na 3 NbO(AsO 4) 2 was prepared by a solid-state reaction. It crystallizes in the monoclinic system, space group P2 1 /n, with a ‫؍‬ 9.637(3) A s , b ‫؍‬ 8.509(2) A s , c ‫؍‬ 10.593(2) A s , ‫؍‬ 108.67(2)°, M ‫؍‬ 455.72, V ‫؍‬ 822.9(4) A s 3 , Z ‫؍‬ 4, ‫؍‬ 3.687 g cm ؊3. The crystal structure was refined (137 variables) from 1440 independent reflections collected on a Nonius CAD4 automatic diffractometer with MoK radiation. The final R index and weighted wR index are 0.022 and 0.045, respectively. The three-dimensional network is built up from NbO 6 octahedra and AsO 4 tetrahedra-sharing corners; each NbO 6 octahedron is bonded to five AsO 4 tetrahedra. This arrangement delimits three different tunnels running along [100], [010], and [001], respectively, at the intersection of which the sodium ions are located in a six-coordination mode. This structure is compared with those of the A 3 MX 2 O 9 (A ‫؍‬ Na, K; M ‫؍‬ Nb, Sb; X ‫؍‬ P, As).

Pre´paration et structure cristalline de K2Nb2As2O11

Journal of Solid State Chemistry, 1988

The crystal structure was refined (105 variables) from 1782 independent reflections collected on a Philips PW 1100 automatic diffractometer with AgKG radiation. The final R index and weighted R, index are 0.058 and 0.056, respectively. The structure consists of Nb06 octahedra and AsO tetrahedra sharing vertices, forming infinite chains (NbOe-AsO& parallel to the a axis. Two chains are linked together by Nb-0-Nb and Nb-O-As bonds. These double chains are connected by vertices, forming a threedimensional network. The potassium atoms are located in tunnels parallel to the a axis. a 1988 Academic Press, Inc.

Caractérisation spectroscopique et étude structurale de RbEr(PO 3 ) 4

Journal de Physique IV (Proceedings), 2004

Crystals of RbEr(PO 3 ) 4 have been grown by the flux technique and characterized by X-ray diffraction, UV-Vis absorbance and infrared spectroscopy. Single crystal structure of RbEr(PO 3 ) 4 has been solved, it crystallizes in the monoclinic P2 1 /n space group with lattice parameters : a = 10,2419(2), b = 8,8349(2), c = 10,9361(2) Å, ß = 106,229(2)°, Z = 4. The crystal structure has been refined yielding a final R(F 2 ) = 0.026 for 2206 independent reflections (F o 2 ≥ 2σ(F o 2 )). The RbEr(PO 3 ) 4 structure is characterized by helical ribbons (PO 3 ) ∞ running along the c-axis. The erbium ions have an eightfold coordination. The ErO 8 polyhedra are isolated from each other in the sense that they do not share any oxygen atom. The minimal distance between two atoms of erbium is 6,2583 Å.

Préparation et Structure Cristalline d'un Nouveau Composé en Couches Rb2MoO2As2O7

Journal of Solid State Chemistry, 1998

A new molybdenylarsenate NaMoO 2 AsO 4 has been isolated. The single-crystal X-ray diffraction study of this phase has shown that it is noncentrosymmetric. It crystallizes in the Pca2 1 (No. 29) space group with a‫,)3(177.41؍‬ b‫,)2(665.6؍‬ c"10.101(1) A s , Z‫,8؍‬ V‫)4(7.979؍‬ A s 3 , R(F 2 ‫,920.0؍)‬ and wR 2 (F 2 ‫370.0؍)‬ for 1209 independent reflections with F 2 > 4 (F 2). The structure consists of MoO 6 octahedra and AsO 4 tetrahedra sharing corners to build up a three-dimensional framework which has large tunnels where the Na ؉ cations reside. Relationships with analogous phosphates and arsenates NaMoO 2 PO 4 , KMoO 2 AsO 4 , KMoO 2 PO 4 , Ba(MoO 2) 2 (PO 4) 2 , and Pb(MoO 2) 2 (PO 4) 2 are discussed.

KNb4AsO13: Preparation et structure cristalline

Journal of Solid State Chemistry, 1988

KNb,AsO,, : Mr = 693.64 crystallizes in the orthorhombic system, space group: Cmcm, a = 10,477(4). b = 10,312(4), c = 10,006(4) A, 2 = 4. The crystal structure was refined from 760 independent reelections. The final R index and weighted R, index are 0.026 and 0.030, respectively. The threedimensional network is constituted of infinite chains (NbO,,-Nb&-AsO*), parallel to the a axis and linked to each other by pairs of edge-sharing octahedra Each pair links together four infinite chains. The potassium ions occupy interconnected cavities parallel to the c axis with an occupancy rate equal to so?G. C 19x8 Acadrmw Pre\\. Inc

Structure en domaines de l'oxyde non centrosymétrique life5O8

Physica status solidi, 1974

La structure en domaines de la forme ordonnee du spinelle LiFe,O, a BtB ktudiBe par microscopie klectronique en transmission. Deux structures Bnantiomorphes P4,32 et P4,32 peuvent germer dans l'oxyde dBsordonn8; en conskcpence deux types de parois d'antiphase sont mis en Bvidence: les parois normales ayant des vecteurs a/2(110) et des parois d'antiphase d'inversion sBparant les domaines knantiomorphes. La nature de ces dBfauts a ktk analyske B l'aide de micrographies en champ sombre dans des conditions de diffraction ti deux ou ti plusieurs faisceaux. The domain structure of the ordered modification of the lithium ferrospinel LiFe,O, has been studied by transmission electron microscopy. Two enantiomorphic structures P4,32 and P4,32 may nucleate in the disordered oxide and consequently two types of antiphase boundaries are detected: normal boundaries with a/2(110) translation vectors and inversion antiphase boundaries. The nature of these defects is analysed using dark field micrographs under two-beam and many-beam diffraction conditions.

Structure cristalline et magnétique de perovskites RBaMn2O6-d (où d=0 et 0.5)

2005

Cette these porte sur la synthese et l'etude des proprietes structurales et magnetiques de perovskites RBaMn2O6-d (ou d = 0 et 0,5). En ce qui concerne le compose YBaMn2O6, les mesures par DSC indiquent que celui-ci subit trois transitions : deux autour de 500K et la troisieme a 750K. L'etude par diffraction des rayons X et de neutrons a montre que la phase de plus haute temperature cristallisait dans le groupe P4/nbm. Les diffractogrammes de rayons X et de neutrons ne presentent qu'un seul changement alors que deux transitions sont observees par DSC au voisinage de 500K. La phase intermediaire a ete affinee dans le groupe d'espace C2/m. La phase d'ordre de charges (en dessous de 500K) etant de basse symetrie, nous avons realise un affinement combine rayons X-neutrons. Les resultats obtenus indiquent un ecart de seulement 15% par rapport a un ordre de charges ideal Mn3+/Mn4+. L'affinement de la structure magnetique et les mesures de susceptibilite magnetique ...