کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1330941 | 978986 | 2009 | 6 صفحه PDF | دانلود رایگان |
The relaxor ferroelectric Pb2Bi4Ti5O18 has been studied by Rietveld refinement of powder neutron diffraction data collected at temperatures of 100, 250 and 400 °C. Our refinements are compatible with the ‘average’ crystal structure of Pb2Bi4Ti5O18 undergoing the phase transition sequence F2mm→I4mm→I4/mmm as a function of increasing temperature, with the latter phase being observed above the known ferroelectric Curie temperature, Tm, and the intermediate phase consistent with a previously observed dielectric anomaly around 207 °C. The results are, however, in conflict with both observation of a symmetry lowering (to space group B2eb) in the lowest temperature phase, observed by electron diffraction, and also with electrical property measurements, which suggest both a- and c-axis polarisation up to Tm. Nevertheless, these crystallographic results are consistent with the observation of relaxor behaviour in this material, and underline the importance of considering ‘long-range’ versus ‘local’ structural effects in relaxor materials.
A powder neutron diffraction study suggests that the relaxor ferroelectric Pb2Bi4Ti5O18 undergoes the phase transition sequence F2mm–I4mm–I4/mmm with increasing temperature.Figure optionsDownload as PowerPoint slide
Journal: Journal of Solid State Chemistry - Volume 182, Issue 10, October 2009, Pages 2626–2631