Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultrahigh permittivity in core-shell ferroelectric ceramics: Theoretical
  approach and practical conclusions   Ferroelectric anomalies in most classical ferroelectric materials such as
BaTiO3 (BT) and related compounds tend to become diffuse and eventually vanish
when the grain size decreases. This has led to question the very existence of
ferroelectricity for very small particles. However there are also reports in
the literature of ultra-high values of permittivity when specific processes or
doping are performed, for instance in the BT-family, or in the CaCu3Ti4O12-
family and interpretations using (IBLC) have been proposed. We have considered
these effects in the framework of a core-shell model of ceramics. The ultrahigh
values mentioned above could be reproduced by considering that the core (be it
dielectric or ferroelectric) have non-zero conductivity. In particular a huge
background of permittivity and a Maxwell Wagner relaxation were obtained in
agreement with the experimental situation. Different types of inhomogeneity
(grain size distribution, mixing of conductive and non-conductive phases,
porosity) have also been considered and their effects are discussed. Finally we
have evaluated the potentiality of energy storage in IBLC compounds and
observed a reduction (compared with non-conductive ferroelectrics) by a factor
2-4 depending on the structuration of the ceramic, which shows that the
performance of such compounds are lower than in optimal insulating core-shell
structures.

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The categories of this paper are: hep-ph
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The categories of this paper are: eess
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
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The categories of this paper are: chao-dyn
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The categories of this paper are: nlin
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The categories of this paper are: math
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph