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Grain Size-Dependent Properties of Dense Nanocrystalline Barium Titanate Ceramics (Articolo in rivista)

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Grain Size-Dependent Properties of Dense Nanocrystalline Barium Titanate Ceramics (Articolo in rivista) (literal)

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Curecheriu L.; Balmus S.-B.; Buscaglia M.T.; Buscaglia V.; Ianculescu A.; Mitoseriu L. (2012)
Grain Size-Dependent Properties of Dense Nanocrystalline Barium Titanate Ceramics
in Journal of the American Ceramic Society (Online); WILEY-BLACKWELL, MALDEN 02148,MA (Stati Uniti d'America)
(literal)

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Curecheriu L.; Balmus S.-B.; Buscaglia M.T.; Buscaglia V.; Ianculescu A.; Mitoseriu L. (literal)

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1,2,6 : Alexandru Ioan Cuza University, Bv. Carol I No. 11, Iasi 700506, Romania / 2 : Gheorghe Asachi Technical University, Bv. D. Mageron, No. 67, Iasi 700050, Romania / 3,4 : Institute of Energetics and Interphases IENI-CNR, Via De Marini No. 6, Genoa I-16149, Italy / 5 : Department of Oxide Materials Science and Engineering, Polytechnics University, 1-7 Gh. Polizu, Bucharest 011061, Romania (literal)

Titolo

Grain Size-Dependent Properties of Dense Nanocrystalline Barium Titanate Ceramics (literal)

Abstract

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 Spark Plasma Sintering (SPS) from ultrafine powders were investigated. The progressive reduction of the Curie 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 GHz range. An interesting feature is the presence of a thermally activated Debye-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. (literal)

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