Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Difference between thermo- and pyroelectric Co- based RE-(= Nd, Y, Gd,
  Ce)-oxide composites measured by high-temperature gradient   Seebeck-Voltage measurements of Cobalt-based oxide-composites containing
rare-earth elements (RE= Nd, Y, Gd, Ce) were performed under high temperature
gradients up to 700 K. Several dependences were measured, Seebeeck voltage as a
function of time U_S(t)or temperature difference U_S(Delta_T), closed circuited
electric current as a function of Seebeck voltage I_S(U_S), or time I_S(t).
While Nd2O3+CoO and Y2O3+CoO show linear n-type US(t)-behavior as usual
thermoelectrics, Gd2O3+CoO possesses a large hysteresis. At both, Gd2O3- and
Ce2O3+CoO also large time dependence I(t) referred to as pyroelectric material
with high capacity were detected. Both anomalies became smaller when Fe2O3 is
added or appear in Nd2O3+CoO and Y2O3+CoO when Al2O3 is added and can be
explained by electron sucking into interfacial space charge regions, a new
materials science challenge.

29
The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess