Nanocomposites and nanomaterials

Conductivity of hydrated nanopowder systems based on zirconia under the influence of an external electric field
Shylo A.V. 1, Doroshkevich A.S.1,2, Danilenko I.A.1, Konstantinova T.E.1, Lyubchyk A.I. 3
1 Materials Science Department, Donetsk Institute for Physics and Engineering named after O.O. Galkin of the NAS of Ukraine, Nauki ave, 46, Kyiv-03028, Ukraine,  e-mail:art.shylo@gmail.com
2Joint Institute for Nuclear Research, 141980, str. Joliot-Curie, 6, Dubna, Russia
3 i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, New University of Lisbon and CEMOP/UNINOVA, Campus de Caparica, 2829-516 Caparica, Portugal

Zirconia is a wide-gap dielectric (band gap = 3.5 ÷ 6 eV) has a relatively high dielectric constant (ε = 25) and high surface chemical activity. For these reasons, nanopowders based on ZrO2 are interesting as working media for electronics and other areas in which energy exchange with the external environment is possible.
The surface of ZrO2 nanoparticles has special electrical properties. As a result of surface bending, a local overlap of a part of electronic orbitals is occurs. It leads to the fact that an electron with certain energy can be localized on any of the atoms in the surface layer of the nanoparticle. The density of localized electron states is largely determined by adsorption. 
The aim of this work was to study the electrical properties of nanopowders based on ZrO2 by the methods of electrochemical impedance spectroscopy under controlled hydration and the influence of an external electric fields.
It is shown that the application of an external constant field up to 3 V / mm with an adsorption moisture content of up to 10 weight percent leads to an increase in the bulk and surface components of the total impedance. Consequently, with an increase in the degree of hydration of the system under conditions of applying a constant bias to the sample, an increase in the charge of the generalized heterophase boundary between the surface of the nanoparticles and the gas phase is observed.
The phenomenon of conductivity of a nanopowder system has a threshold character and depends on the concentration of adsorbates on the surface of the nanoparticle. It is shown that the adsorbates in the ionized state provide not only the increase in the conductance of the surface of the nanoparticles, but also the transfer via the relay mechanism of charge in the sample volume.