%0 Journal Article
%T CaCo<sub>1-x</sub>Ru<sub>x</sub>O<sub>y</sub>: Role of Ru/Co Ratio on Its Transport Properties
%A Sezhian Annamalai
%A Rudra P. Bhatta
%A Jugdersuren Battogtokh
%A Ian L. Pegg
%A Biprodas Dutta
%J New Journal of Glass and Ceramics
%P 8-17
%@ 2161-7562
%D 2014
%I Scientific Research Publishing
%R 10.4236/njgc.2014.41002
%X <p>
	<span>Calcium
cobaltites, especially Ca<sub>3</sub>Co<sub>4</sub>O<sub>9</sub></span><span> </span><span>with a misfit layered structure, are promising
thermoelectric materials due to their suitability for high temperature
applications and low densities. T</span><span>he
existence of low spin-state electronic configurations for both <img src=\"Edit_97603788-21eb-4a70-93ef-76538a98dab7.bmp\" alt=\"\" /></span><span></span><span> and <img src=\"Edit_c1d37ea5-791a-4188-b5ad-d3c64c44e0d3.bmp\" alt=\"\" /></span><span> </span><span>species is one of the key parameter to explain the
large thermopower values. Ruthenium
oxide, with a layered structure, exhibits
strong electron-electron correlation</span><span> </span><span>and the extended nature of their 4<i>d</i> electrons
enhances orbital overlapping which is expected to influence the transport
characteristics of CaCo<sub>1-<i>x</i></sub>Ru<i><sub>x</sub></i>O<i><sub>y</sub></i> (CCR) samples,
by affecting the spin state of the 3<i>d</i> Co ions. The effect on thermopower
and electrical resistivity due to</span><span> </span><span>partial substitution of Co by Ru ions, up to 0.33 moles,
from 300 to 600 K was investigated. A sharp decline in resistivity and in thermopower
was observed until a transition ion ratio (<i>TIR</i>),
(Ru/(Ru</span><span> </span><span>+</span><span> </span><span>Co)), of 0.5 is reached, beyond which both the
properties became less sensitive to <i>TIR</i>.
These variations in the transport properties are explained by the presence of 4<i>d</i> Ru in close proximity to the Co, which could influence the spin and oxidation
state of Co ions. The Co rich and Ru rich samples exhibit very distinct
microstructures and phase assemblages.</span> 
</p>
%K Calcium Cobaltite
%K Ruthenium Oxide
%K Calcium Ruthenate
%K Transport Properties
%K Thermoelectric Properties
%K Seebeck Coefficient
%K Resistivity
%U http://www.scirp.org/journal/PaperInformation.aspx?PaperID=42570