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.

Structure D 2000BiScO 3 : Centrosymmetric BiMnO 3 -Type Oxide. -The title compound is synthesized from Bi2O3 and Sc2O3 in a belt-type high-pressure apparatus (6 GPa, 1413 K, 40 min). As revealed by powder XRD and powder neutron diffraction, BiScO3 crystallizes in the monoclinic space group C2/c. BiScO3 may serve as a model system to understand the role of Mn 3+ ions in ferroelectricity of BiMnO3. -(BELIK*, A. A.; et al.; J.

Structure D 2000Crystallographic Features and Tetragonal Phase Stability of PbVO 3 , a New Member of PbTiO3 Family. -The crystallographic properties of the title compound are characterized by synchrotron powder XRD between 12 and 570 K. At 300 K, PbVO3 crystallizes in the tetragonal space group P4mm with Z = 1 and is isotypic with PbTiO3. The tetragonal phase is stable over the whole temperature range studied. Under applied pressure, a tetragonal-to-cubic phase transition accompanied by an insulator-to-metal transition starts at ≈2 GPa at room temperature. -(BELIK*, A. A.; AZUMA, M.; SAITO, T.; SHIMAKAWA, Y.; TAKANO, M.; Chem. Mater. 17 (2005) 2, 269-273; Inst. Chem. Res., Kyoto Univ., Uji, Kyoto 611, Japan; Eng.) -W. Pewestorf