Colossal thermoelectric power in charge ordered lanthanum calcium manganites (La0.5Ca0.5MnO3) (original) (raw)

Observation of large thermoelectric power in charge ordered La1−xLixMnO3 (x = 0.25) manganite system

Indian Journal of Physics, 2016

In the present investigation detailed structural, electrical, magnetic and thermoelectric measurements on bulk samples of Li-doped La 1-x Li x MnO 3?d (0.05 B x B 0.3) manganites have been done. The samples are synthesized by wetchemical mixing route and XRD analysis using Rietveld refinement revealed single phase behaviour upto Li-concentration x = 0.25. All the samples in the present series show ferromagnetic behaviour while metallic behaviour is shown by the samples upto Li concentration x = 0.2. Beyond x = 0.2 the sample (i.e., La 0.75 Li 0.25 MnO 3) show insulating behaviour for the entire temperature range accompanied by charge-order transition around T = 225 K. The low temperature resistivity data are best fitted by q(T) = q 0 ? q 4.5 T 4.5 ? C/sinh 2 (ht s /2k B T), where C is a constant. Such behaviour might be an indication of the small-polaron coherent motion which involves a relaxation due to a soft optical phonon mode that is strongly coupled to the carriers. Thermoelectric power (TEP) measurements reveal interesting results showing a colossal value of-340 lV/K around 25 K for the CO sample in the present series. The probable mechanism responsible for the observed large TEP has been discussed here.

La 1-x Ca x MnO 3 semiconducting nanostructures: morphology and thermoelectric properties

Nanoscale research letters, 2014

Semiconducting metallic oxides, especially perosvkite materials, are great candidates for thermoelectric applications due to several advantages over traditionally metallic alloys such as low production costs and high chemical stability at high temperatures. Nanostructuration can be the key to develop highly efficient thermoelectric materials. In this work, La 1-x Ca x MnO 3 perosvkite nanostructures with Ca as a dopant have been synthesized by the hydrothermal method to be used in thermoelectric applications at room temperature. Several heat treatments have been made in all samples, leading to a change in their morphology and thermoelectric properties. The best thermoelectric efficiency has been obtained for a Ca content of x=0.5. The electrical conductivity and Seebeck coefficient are strongly related to the calcium content.

Effect of Ca(Ce) doping on thermopower of LaMnO[sub 3] manganites

Low Temperature Physics, 2010

With a view to explain the thermoelectric effects of La 0.8 Ca 0.2 MnO 3 and La 0.8 Ce 0.2 MnO 3 polycrystalline samples and to seek the role of scattering mechanism, a systematic investigation of thermopower S(T) in the metallic phase have been undertaken. Within the relaxation time approximation, it is noticed that, the phonon drag S(T) with scattering of phonons from defects, grain boundaries, phonons and charge carriers in these samples are effective in the metallic regime. Later on, Mott expression is employed to incorporate the carrier diffusive thermopower. The temperature dependence of the S(T) is determined by competition among the several operating scattering mechanisms for the heat carriers and a balance between carrier diffusion and phonon drag contributions in the polycrystalline samples of La 0.8 Ca 0.2 MnO 3 and La 0.8 Ce 0.2 MnO 3 .