Electrical conductivity of synthesized Zircon ceramics doped with different dopants
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Date
2006
Authors
Fervin, S. Z. R.
Journal Title
Journal ISSN
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Publisher
University of Peradeniya
Abstract
The electrical conductivity enhancement of laboratory synthesized zircon ceramics, doped with different dopants has been studied using complex impedance spectroscopy. The cation dopants used in this study were Y³⁺ Fe³⁺ Yb³⁺, Mg²⁺, Ca²⁺, Na ²⁺ Er³⁺, Na ²⁺+Y³⁺ and Na⁺+ Fe³⁺ It is expected, that the presence of defects in the zircon host structure introduced by doping can lead to higher electrical conduction.
First, X-Ray Diffraction (XRD) analysis was performed on the zircon samples doped different cations to find out whether zircon formation was successful. Then, the ‘complex impedance measurements were performed as a function of temperature.
The XRD analysis shows that, the formation of zircon was successful in the samples doped with 10 mol % Y₂0₃ 10 mol % Fe₂O₃, 10 mol % Yb₂O₃, 10 mol % MgO, 10 mol % CaO and 10 mol % Er₂O₃. The electrical conductivity of synthesized zircon ceramics increased with increasing temperature irrespective of the dopant. A good conductivity enhancement was obtained in zircon doped with 10 mol % Y₂0₃ and 10 mol % Fe₂0₃ which were 2.47x10⁻⁵ S cm⁻¹ and 1.33x10⁻⁵ S cm⁻¹ at 700 °C respectively. These values are nearly equal to the data reported in literature for natural zircon.
The conductivity enhancement in zircon samples doped with Y₂O₃ and Fe₂O₃ is most probably due to the motion of O²⁻ ions by vacancy mechanism. The O²⁻ ion vacancies were created as a consequence of the substitution of Y³⁺ and Fe³⁺for Zr⁴⁺or Si⁴⁺. For substitution to take place the ions must be comparable in size. This indicates that, the ionic radii of Y³⁺ and Fe³⁺ are comparable to that of Zr⁴⁺or Si⁴⁺, However, the zircon samples doped with Yb₂0₃, MgO, CaO and Er₂O₃ did not show any significant conductivity enhancement. This may be due to non-incorporation of these dopants into the host structure of zircon to give a defect structure as a result of the difference in ionic radii of the cations. Hence, O²⁻ vacancies were not created and the conductivity was not increased.
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Keywords
Physics of materials , Ceramics