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La3+-induced (micro)structural changes and origin of the relaxor-like phase transition in ferroelectric lead barium niobate electroceramics


Lead barium niobate (Pb1−x Ba x Nb2O6, PBN) ferroelectric materials have been and are the subject of numerous studies in literature due to their potential for wide-ranging applications in the electronic industry. In this work, La3+-doped Pb0.56Ba0.44Nb2O6 (PBN44) electroceramics were prepared and investigated in terms of X-ray diffraction, scanning electron microscopy, thermal spectra of dielectric permittivity, Curie–Weiss law, and hysteresis loop characteristics. It was noted that La3+ doping favors the formation of orthorhombic mm2 phase in PBN44, which originally shows only the tetragonal 4mm symmetry-related phase. In particular, the PBN44 material with 1 wt% La2O3 displays (micro)structural characteristics and dielectric properties similar to those from PBN compositions lying within their morphotropic phase boundary region. Our results also show that La3+ is able to promote a change of the ferroelectric to paraelectric phase transition appearance of PBN44 from pseudo-normal to really diffuse. However, conversion to a diffuse plus relaxor transition behavior reveals directly linked to incommensurate superstructures present and dielectrically-active in PBN materials toward low temperatures, with an intrinsically frequency-dispersive dielectric response. This statement is also supported by observation of hysteresis loops showing a transformation trend to pseudo-slim-like, even in the normal-like ferroelectrics, when moving into the temperature region of incommensuration manifestation.

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This work was supported by FAPESP and CNPq, two Brazilian research-funding agencies. Support from MAT2010-21088-C03-02 research project of the Spanish Government is also grateful. The authors gratefully acknowledge technical assistance from Francisco J. Picon. J. E. García wishes to thank Erasmus Mundus External Cooperation Window EU-Brazil Startup project and JPI-2012 Santander-Universidades program for their financial support.

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Correspondence to Michel Venet.

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Venet, M., Zabotto, F.L., Garcia, J.E. et al. La3+-induced (micro)structural changes and origin of the relaxor-like phase transition in ferroelectric lead barium niobate electroceramics. J Mater Sci 49, 4825–4832 (2014).

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  • Hysteresis Loop
  • Dielectric Permittivity
  • La2O3
  • Morphotropic Phase Boundary
  • Hysteresis Loop Measurement