Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Colossal dielectric constants in single-crystalline and ceramic
  CaCu3Ti4O12 investigated by broadband dielectric spectroscopy   In the present work the authors report results of broadband dielectric
spectroscopy on various samples of CaCu3Ti4O12, including so far only rarely
investigated single crystalline material. The measurements extend up to 1.3
GHz, covering more than nine frequency decades. We address the question of the
origin of the colossal dielectric constants and of the relaxational behavior in
this material, including the second relaxation reported in several recent
works. For this purpose, the dependence of the temperature- and
frequency-dependent dielectric properties on different tempering and surface
treatments of the samples and on ac-field amplitude are investigated. Broadband
spectra of a single crystal are analyzed by an equivalent circuit description,
assuming two highly resistive layers in series to the bulk. Good fits could be
achieved, including the second relaxation, which also shows up in single
crystals. The temperature- and frequency-dependent intrinsic conductivity of
CCTO is consistent with the Variable Range Hopping model. The second relaxation
is sensitive to surface treatment and, in contrast to the main relaxation, also
is strongly affected by the applied ac voltage. Concerning the origin of the
two insulating layers, we discuss a completely surface-related mechanism
assuming the formation of a metal-insulator diode and a combination of surface
and internal barriers.

10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas