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Ionic conductivity enhancement in Gd2Zr2O7 pyrochlore by Nd doping

Published online by Cambridge University Press:  31 January 2011

B.P. Mandal,
S.K. Deshpande and
A.K. Tyagi
B.P. Mandal
Affiliation:
Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
S.K. Deshpande
Affiliation:
University Grants Commission—Department of Atomic Energy (UGC-DAE) Consortium for Scientific Research, Bhabha Atomic Research Centre, Mumbai 400085, India
A.K. Tyagi*
Affiliation:
Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
*
a)Address all correspondence to this author. e-mail: aktyagi@barc.gov.in
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Abstract

The pyrochlore compositions Gd2–yNdyZr2O7 (y = 0.0, 0.1, 0.4, 0.6, 1.0, 1.4, 1.6, and 2.0) were synthesized, and their ionic conductivity was determined (100 Hz–15 MHz, 622–696 K). The direct-current (dc) conductivity (σdc) varies upon Nd substitution at the Gd site, and a peaking effect in σdc was observed around y = 1.0. This indicates that a significant increase in conductivity can be obtained at moderately high temperatures by suitable doping at the Gd site with isovalent rare-earth ions like Nd. The extent of oxygen ion disorder determined from x-ray diffraction was found to decrease with increasing Nd content. The dc conductivity obeys the Arrhenius relation σdcT = σ0 exp(−E/kBT). The activation energy E and the preexponential factor σ0, which is a measure of the concentration of the mobile species, increase while going from the ordered Nd2Zr2O7 to the least ordered Gd2Zr2O7. These two processes presumably lead to the peaking of σdc at an intermediate Nd content. Our results also suggest that the cooperative motion of mobile ions does not contribute much to the increase in activation energy in this compound.

Keywords

Electrical propertiesX-ray diffraction (XRD)

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Type
Articles
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Journal of Materials Research , Volume 23 , Issue 4 , April 2008, pp. 911 - 916
Copyright
Copyright © Materials Research Society 2008

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