Rene Macquart et al 2002 J. Phys.: Condens. Matter 14 7955 doi:10.1088/0953-8984/14/34/314
Rene Macquart1, Brendan J Kennedy1, Brett A Hunter2 and Christopher J Howard2,3
Show affiliationsA high-resolution synchrotron diffraction study of the temperature dependence of the structures of the two layered Bi oxides PbBi2Ta2O9 (PBT) and PbBi2Nb2O9 (PBN) is reported. The transition from the low-temperature orthorhombic ferroelectric structure to the high-temperature tetragonal paraelectric structure in PBN involves an intermediate orthorhombic paraelectric phase. We conclude that this has the same Amam structure as observed in SrBi2Ta2O9 and its Bi-rich analogue. Identifying the sequence of phase transitions in PBT is more challenging since above 200 °C the structure is metrically tetragonal within the resolution of the synchrotron diffraction measurements. By contrast, neutron diffraction measurements suggest that PBT remains orthorhombic to above the Curie temperature ≈430°C. The possible identity of the intermediate space group is discussed.
77.80.Bh Phase transitions and Curie point
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
Issue 34 (2 September 2002)
Received 5 June 2002
Published 15 August 2002
Rene Macquart et al 2002 J. Phys.: Condens. Matter 14 7955
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