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Grain Size‐Dependent Properties of Dense Nanocrystalline Barium Titanate Ceramics
Author(s) -
Curecheriu Lavinia,
Balmus SorinBogdan,
Buscaglia Maria Teresa,
Buscaglia Vincenzo,
Ianculescu Adelina,
Mitoseriu Liliana
Publication year - 2012
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2012.05409.x
Subject(s) - materials science , nanocrystalline material , grain size , barium titanate , permittivity , ceramic , dielectric , grain boundary , ferroelectric ceramics , ferroelectricity , condensed matter physics , composite material , relaxation (psychology) , mineralogy , nanotechnology , microstructure , optoelectronics , chemistry , physics , psychology , social psychology
The grain size influence on the dielectric relaxation and nonlinear dielectric properties of BaTiO 3 ceramics with grain size in the range of (92÷936) nm densified by S park P lasma S intering ( SPS ) from ultrafine powders were investigated. The progressive reduction of the C urie temperature and of the effective permittivity results from a combination of intrinsic size effects and low‐permittivity grain boundary layer. A model of dielectric cylindrical cavities was employed in order to calculate intrinsic effective permittivity values in GH z range. An interesting feature is the presence of a thermally activated D ebye‐like relaxation in the ferroelectric state of ceramics with grain size above 300 nm, with activation energies of 0.45–0.49 eV, which seems to be related to the domain walls forced motion under the applied field. By diminishing grain size, a progressive reduction of the ferroelectric nonlinear character was obtained, reaching a macroscopic non‐switching character and a linear permittivity versus field dependence for the finest ceramics (grain size of 90–100 nm) until very high values of the applied field. The observed behavior supports the idea of frozen polarization induced by pinning centers as due to a large number of grain boundaries and charged defects in the fine structures.