Effect of Ca(Ce) doping on thermopower of LaMnO3 manganites

Abstract

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 .

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

“…19 From a fundamental perspective, factors like double exchange, Jahn-Teller distortion, crystal structure, charge ordering, magnon scattering, phonon scattering, spin-glass effect, and grain size have a profound influence on the colossal thermoelectric power. [20][21][22] Large band width manganites possess high electrical conductivity; however, they have small values of Seebeck coefficient. 23 Intermediate band width manganites based on calcium, especially, the charge ordered composition, La 0.5 Ca 0.5 MnO 3 , is interesting not only from a fundamental but also from an applied perspective as they are likely to exhibit colossal thermoelectric power as observed in Gd 0.5 Sr 0.5 MnO 3 .…”