ICMA UZ CSIC

Villanueva del Río y Minas, Spain

ICMA UZ CSIC

Villanueva del Río y Minas, Spain

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Constantinescu G.,ICMA UZ CSIC | Rasekh Sh.,ICMA UZ CSIC | Torres M.A.,University of Zaragoza | Diez J.C.,ICMA UZ CSIC | And 2 more authors.
Journal of Alloys and Compounds | Year: 2013

Ca3-xSrxCo4O9 polycrystalline thermoelectric ceramics with small amounts of Sr have been synthesized by the classical solid state method. Microstructural characterizations have shown that all the Sr has been incorporated into the Ca3Co4O9 and Ca3Co2O 6 structures and no Sr-based secondary phases have been produced. Apparent density measurements have shown that samples slightly increase their density until 0.05 Sr content, decreasing for higher contents. Electrical resistivity decreases and Seebeck coefficient slightly raises when Sr content increases until 0.07 Sr addition. The improvement in both parameters leads to higher power factor values than the usually obtained in samples prepared by the conventional solid state routes and close to those obtained in textured materials. © 2013 Elsevier B.V. All rights reserved.


Diez J.C.,ICMA UZ CSIC | Torres M.A.,University of Zaragoza | Rasekh S.,ICMA UZ CSIC | Constantinescu G.,ICMA UZ CSIC | And 2 more authors.
Ceramics International | Year: 2013

Ca3Co4-xCrxO9 polycristalline thermoelectric ceramics with small amounts of Cr have been synthesized by the classical solid state method. Microstructural characterizations have shown that all the Cr has been incorporated into the Ca3Co4O 9 structure and no Cr-containing secondary phases have been produced for Cr contents≤0.05. Apparent density measurements have shown that all samples are very similar, with densities around 75% of the theoretical one. Electrical resistivity decreases and Seebeck coefficient slightly raises when Cr content increases until 0.05 Cr addition. The improvement in both parameters leads to higher power factor values than the usually obtained by conventional solid state routes. © 2013 Elsevier Ltd and Techna Group S.r.l.


Constantinescu G.,ICMA UZ CSIC | Rasekh S.H.,ICMA UZ CSIC | Torres M.A.,University of Zaragoza | Chocarro C.,University of Lleida | And 3 more authors.
Boletin de la Sociedad Espanola de Ceramica y Vidrio | Year: 2014

Ca3-xMgxCo4O9 polycrystalline thermoelectric ceramics with small amounts of Mg have been synthesized by the classical solid state method. Microstructural characterizations have shown that all the Mg has been incorporated into the Ca3Co4O 9 structure and no Mg-based secondary phases have been identified. Apparent density measurements have shown that samples do not modify their density until 0.05 Mg content, decreasing for higher contents. Electrical resistivity decreases and Seebeck coefficient slightly raises when Mg content increases until 0.05 Mg addition. The improvement in both parameters leads to higher power factor values than the usually obtained in samples prepared by the conventional solid state routes and close to those obtained in textured materials.


Constantinescu G.,ICMA UZ CSIC | Constantinescu G.,University of Duisburg - Essen | Rasekh S.,ICMA UZ CSIC | Torres M.A.,ICMA UZ CSIC | And 4 more authors.
Ceramics International | Year: 2015

Ca3-x Na x Co4O9 polycrystalline thermoelectric ceramics with small amounts of Na (x=0, 0.01, 0.03, 0.05, 0.07, and 0.10) have been prepared using the classical solid state method. Microstructural characterization has shown that Na has been incorporated into the Ca3Co4O9 phase and that no Na-based secondary phases have been produced. It has also been found that Na addition promotes grain growth and favours sintering due to the formation of a small amount of liquid phase. Electrical resistivity decreases when Na content increases until 0.07Na addition while Seebeck coefficient is maintained practically unchanged. The improvement in electrical resistivity leads to higher power factor values than the usually obtained in samples prepared by more complex and expensive techniques. © 2015 Elsevier Ltd and Techna Group S.r.l.


Sotelo A.,ICMA UZ CSIC | Guilmeau E.,CNRS Crystallography and Material Science Laboratory | Rasekh S.H.,ICMA UZ CSIC | Madre M.A.,ICMA UZ CSIC | And 2 more authors.
Journal of the European Ceramic Society | Year: 2010

Thermoelectric performances on cobaltite ceramics can be changed by doping followed by grain orientation methods. This can be performed by the Laser Floating Zone (LFZ) method on samples with different substitutions in the Rock Salt sublattice. In this work, Bi2-xPbxCa2Co1.7Oy (x=0.0, 0.2, 0.4 and 0.6) ceramics have been directionally grown at 30mm/h. In all the cases, samples show a microstructure composed, mainly, of alternated grains of the thermoelectrical phase and the solid solution Bi(Pb)-Ca-O, with small CoO inclusions. It has been found an important improvement on the resistivity and thermopower for samples with 0.4 Pb substitution, leading to power factor values higher than usual in misfit cobaltites obtained by conventional solid state routes. © 2010 Elsevier Ltd.

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