High-Pressure Synthesis, Crystal Structures, and Properties of Perovskite-like BiAlO₃ and Pyroxene-like BiGaO₃

Abstract

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.

Rashba-Dresselhaus spin-splitting in the bulk ferroelectric oxideBiAlO3

“…24 This was later confirmed in samples synthesized on high temperature and high pressure conditions. 25 The calculated polarization value 24 was of 75.6 µC/cm 2 ; however, reported values for measurements done in polycrystalline samples 26,27 are 9.5 and 12 µC/cm 2 . To the best of our knowledge, there is only one report about thin-film growth of BAO.…”

“…Rhombohedral and tetragonal crystalline structures of BAO were examined. For the rhombohedral case (space group R3c), the experimental lattice parameters and atomic positions 25 were used as a starting point and a relaxation of the internal atomic positions was performed using a 6 × 6 × 6 k-point mesh containing the Γ point. The hexagonal setting for the unit cell was also considered, since it allows for a more direct and intuitive interpretation of the results.…”

“…The unit cell in hexagonal setting is the same as in Refs. [24][25][26]. Due to the lack of published crystallographic data regarding the tetragonal phase of BAO, a prototypical centrosymmetric tetragonal structure (space group P4mm) was constructed using the reported lattice parameters.…”

High-pressure synthesized materials: treasures and hints

“…Recently high-pressure synthesis was successfully applied to fabricate new class of materials -multiferroic substances [63] such as BiMnO 3 , BiAlO 3 , BiGaO 3 , BiFeO 3 etc. These materials with perovskite-like structure possess simultaneously ferromagnetic and ferroelectric properties (magnetic moment and spontaneous electric polarization).…”

Phase Transition of BiFe1-xAlxO3 Films Prepared by Chemical Solution Deposition

“…Researches on polar perovskite-type crystal, such as BiMO 3 (M=Al, Ga, In, and Co) have been intensively done. [4][5][6] Belik et al [7] reported that a large family of polar materials with R3c and Cm symmetries was found for solid solution of BiFe 1-x Al x O 3 under high-pressure and high-temperature. However, there is no such study focused on Al doped BFO.…”