Bismuth I 5400High-Pressure Synthesis, Crystal Structures, and Properties of Perovskite-Like BiAlO3 and Pyroxene-Like BiGaO3. -The title compounds are synthesized from stoichiometric mixtures of Bi2O3 and Al2O3 or Ga2O3 (6 GPa, 1273-1473 K, 40-15 min). As revealed by powder XRD, BiAlO3 crystallizes in the space group R3c with Z = 6. It is isotypic with multiferroic perovskite-like BiFeO3 and has octahedrally coordinated Al 3+ ions. Time-of-flight neutron powder diffraction shows that BiGaO 3 crystallizes in the space group Pcca with Z = 4. Its structure is closely related to pyroxene-like KVO3. The structure contains infinite ] chains of corner-sharing GaO4 tetrahedra. Both compounds decompose at ambient pressure on heating above 820 K to give Bi2M4O9 and Bi25MO39 (M: Al, Ga). -(BELIK*, A. A.; WUERNISHA, T.; KAMIYAMA, T.; MORI, K.; MAIE, M.; NAGAI, T.; MATSUI, Y.; TAKAYAMA-MUROMACHI, E.; Chem.
Solid solutions BiMn 1-x Sc x O 3 (0 e x e 1) were prepared at 6 GPa and 1383-1443 K. Selected area and convergent beam electron diffraction showed that BiMn 0.9 Sc 0.1 O 3 crystallizes in the centrosymmetric space group C2/c at room temperature. The structure parameters of BiMn 0.9 Sc 0.1 O 3 were refined by the Rietveld method from laboratory X-ray diffraction data (Z ) 8; a ) 9.6029(3) Å, b ) 5.60988( 14) Å, c ) 9.7690(3) Å, β ) 108.775(2°) at 293 K). The Mn-O bond lengths suggest that the orbital order present in BiMnO 3 at 300 K disappears in BiMn 0.9 Sc 0.1 O 3 . Therefore, the monoclinic-to-monoclinic phase transition observed in BiMnO 3 at 474 K and associated with the orbital melting was not detected in BiMn 1-x Sc x O 3 for x g 0.05 down to 133 K. BiMn 1-x Sc x O 3 were characterized by dc and ac magnetization, specific heat, and differential scanning calorimetry measurements. The long-range ferromagnetic order seems to survive for x ) 0-0.2. For x g 0.4, the samples showed spin-glass-like features. The Weiss temperature deduced from the fitting of magnetic susceptibilities was positive for all the compositions with x < 1 and decreased monotonically with increasing x. The temperature of the magnetic transitions decreased and the temperature of the structural monoclinic-to-orthorhombic phase transition increased (from 768 K for x ) 0 to 840 K for x ) 0.3) with increasing x.
In order to clarify the existence of a single sheet of carbon six-membered-ring plane (graphene) this letter presents a method by which the stacking number of the sheets in a carbon nanofilm (CNF) can be exactly counted, based on the quantitative analysis of electron diffraction intensity. Using the method we can detect a single graphene sheet in a CNF.
The sodium rhodate NaRh 2 O 4 was synthesized for the first time and characterized by neutron and X-ray diffraction studies and measurements of magnetic susceptibility, specific heat, electrical resistivity, and the Seebeck coefficient. NaRh 2 O 4 crystallizes in the CaFe 2 O 4 -type structure, which is comprised of a characteristic RhO 6 octahedral network. The compound is metallic in nature, probably reflecting the 1:1 mixed valence character of Rh(III) and Rh(IV) in the network. For further studies of the compound, the Rh valence was varied significantly by means of an aliovalent substitution: the full-range solid solution between NaRh 2 O 4 and CaRh 2 O 4 was achieved and characterized as well. The metallic state was dramatically altered, and a peculiar magnetism developed in the low Na concentration range.
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