Publication Date:
2011-06-15
Description:
The phase transitions in unpoled lead-free (1− x )(Bi 1/2 Na 1/2 )TiO 3 – x BaTiO 3 ( x = 0.06 and 0.11) ceramics are investigated using hot-stage transmission electron microscopy (TEM). It is found that large ferroelectric domains in both ceramics start to disappear around T d , the depolarization temperature. After the transition, both compositions exhibit the P 4 bm tetragonal symmetry in the form of nanodomains. The structural transition observed by the in situ TEM experiments seems to be gradual and occurs within a temperature range of several tens of degrees, in contrast to the sharp anomaly at T d revealed by the dielectric characterization. With further increasing temperature, no structural change was observed for both compositions across T RE , where the dielectric frequency dispersion vanishes, and T m , where the dielectric permittivity reaches maximum. The tetragonal-to-cubic transition is diffuse and takes place in a broad temperature window well above both T RE and T m . These results of structural phase transitions are summarized in a phase diagram with its composition range covering the morphotropic phase boundary (MPB).
Print ISSN:
0002-7820
Electronic ISSN:
1551-2916
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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