New oxides, BiAlO 3 and BiGaO 3 , were prepared using a high-pressure high-temperature technique at 6 GPa and 1273-1473 K. BiAlO 3 is isotypic with multiferroic perovskite-like BiFeO 3 and has octahedrally coordinated Al 3+ ions. Structure parameters of BiAlO 3 were refined from laboratory X-ray powder diffraction data (space group R3c; Z ) 6; a ) 5.37546(5) Å and c ) 13.3933(1) Å). BiGaO 3 has the structure closely related to pyroxene-like KVO 3 . Structure parameters of BiGaO 3 were refined from timeof-flight neutron powder diffraction data (space group Pcca; Z ) 4; a ) 5.4162(2) Å, b ) 5.1335(3) Å, and c ) 9.9369(5) Å). The GaO 4 tetrahedra in BiGaO 3 are joined by corners forming infinite (GaO 3 ) 3chains along the a axis. Bi 3+ ions in BiGaO 3 have 6-fold coordination. Both BiAlO 3 and BiGaO 3 decompose at ambient pressure on heating above 820 K to give Bi 2 M 4 O 9 and Bi 25 MO 39 (M ) Al and Ga). Vibrational properties of BiAlO 3 and BiGaO 3 were studied by Raman spectroscopy. In solid solutions of BiAl 1-x Ga x O 3 , a C-centered monoclinic phase structurally related to PbTiO 3 with lattice parameters of a ) 5.1917(4) Å, b ) 5.1783(4) Å, c ) 4.4937(3) Å, and β ) 91.853(3)°was found.

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.

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