The ac electrical conductivity and dielectric relaxation properties of nanocrystalline 20 mol% Ho doped ceria (Ce0.8Ho0.2O2-δ) prepared by citrate auto ignition method, were studied in the temperature range 300-550 °C. The conductivity behaviour showed the absence of any precipitation of Ho inside the grains, even though it has the tendency of forming a C-type structure similar to Ho2O3 in association with oxygen vacancies. The frequency spectra of electric modulus M″ exhibits a single relaxation peak corresponding to relaxation reorientation of oxygen vacancy around the Ho+3 ions in the cubic nanostructured material. The migration of oxygen ions in the nanocrystalline Ce0.8Ho0.2O2-δ material takes place through hopping and the migration energy and association energy of oxygen vacancies in the long range order motion are found to be 1.02 and 0.24 eV, respectively. © 2009 Elsevier B.V. All rights reserved.

Sankaranarayanan V

Department Of Physics

AC ELECTRICAL CONDUCTIVITIES

ASSOCIATION ENERGIES

AUTO IGNITIONS

C-TYPE STRUCTURES

electric modulus

FREQUENCY SPECTRUMS

ION TRANSPORTS

Long range orders

MIGRATION ENERGY

NANOCRYSTALLINE HO DOPED CERIA

Oxygen ions

SINGLE RELAXATIONS

STRUCTURAL INHOMOGENEITY

Temperature ranges

Cerium

CERIUM COMPOUNDS

Dielectric relaxation

electric conductivity

Holmium

Ions

Nanocrystalline materials

Nanostructured materials

Oxygen

Vacancies

Oxygen vacancies

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

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IIT Madras

Physica B: Condensed Matter

The ionic transport properties of nanocrystalline 20 mol% Eu, Gd, Dy, and Ho doped cerias, with average grain size of around 14 nm were studied by correlating electrical, dielectric properties, and various dynamic parameters. Gd-doped nanocrystalline ceria shows higher value of conductivity (i. e., 1. 8 × 10 -4 S cm -1 at 550°C) and a lower value of association energy of oxygen vacancies with trivalent dopants Gd 3+ (i. e., 0. 1 eV), compared to others. Mainly the lattice parameters and dielectric constants (ε ∞) are found to control the association energy of oxygen vacancies in these nanomaterials, which in turn resulted in the presence of grain and grain boundary conductivity in Gd- and Eu-doped cerias and only significant grain interior conductivity in Dy- and Ho-doped cerias. © The Author(s) 2010.

Fulltext

Nanoscale Research Letters

Ionic Transport Properties in Nanocrystalline Ce 0.8A 0.2O 2-δ (with A = Eu, Gd, Dy, and Ho) Materials

Electrical and dielectric properties, and their correlations were discussed in the nanostructured Ce0.8 Dy0.2 O2-δ materials with average grain sizes of 15, 35, and 58 nm using the dielectric functions such as dielectric permittivity (ε′), loss tangent (tan δ), and electric modulus (M″). The ionic transport mechanism varies with the grain size of the materials such that the material with an average grain size of 35 nm exhibited a higher value of ionic conductivity above 440°C (with σ=8.96× 10-4 S cm-1 at 550°C), whereas the material with an average grain size of 15 nm shows higher value conductivity at lower temperatures. The oxygen vacancy in the material decreases with the decrease in grain size. The migration energy of oxygen ions also decreases with the decrease in grain size of the nanostructured Ce0.8 Dy 0.2 O2-δ material. The material with an average grain size of 35 nm shows a very low value association energy (i.e., 0.05 eV) compared to the others. At temperatures below 420°C, the local motion of oxygen vacancies around Dy+3 controls the conductivity of all the materials, and at higher temperatures, the conductivity in the materials with a larger grain size is mainly due to the long-range motion of vacancies. © 2010 The Electrochemical Society.

Journal of the Electrochemical Society

Grain size effect on electrical and dielectric properties of the nanostructured Dy-doped ceria (Ce0.8 Dy0.2 O 2-δ)

Ionic conductivity and electrical relaxation of nanocrystalline scandia-stabilized c-zirconia using complex impedance analysis

Renewable Energy

Comparison between Y-doped ceria and Ho-doped ceria: Electrical conduction and microstructures

Journal of The Electrochemical Society

Microstructural Inhomogeneity in Holmium-Doped Ceria and Its Influence on the Ionic Conduction

Journal of Materials Science

Gadolinia doped ceria/yttria stabilised zirconia electrolytes for solid oxide fuel cell applications

Solid State Ionics

Oxygen transport in La0.6Sr0.4Co0.2Fe0.8O3−δ

Ion transport and dielectric relaxation studies in nanocrystalline Ce0.8Ho0.2O2-δ material

Journal	Physica B: Condensed Matter
ISSN	09214526
Open Access	No