Enhanced thermopower upon Ni substitution in Na0.75CoO2

TL;DR

This study investigates how substituting Ni into Na0.75CoO2 enhances its thermopower across a wide temperature range, with notable increases at room temperature and low-temperature anomalies, indicating potential for thermoelectric applications.

Contribution

It demonstrates that Ni substitution systematically increases thermopower and alters electrical properties in Na0.75CoO2, revealing new insights into doping effects on thermoelectric materials.

Findings

Room temperature TEP increases by 20μV/K with 1% Ni substitution.

TEP shows a low-temperature peak around 20K in substituted samples.

Ni substitution decreases resistivity, enhancing thermoelectric performance.

Abstract

Thermopower measurements have been carried out on the Ni substituted samples of Na0.75CoO2 in the temperature range 4.2K to 300K. The room temperature TEP increases by 20microV/K even with 1% Ni substitution and systematically increases with increasing Ni content upto 5%. The increase in TEP is accompanied by a decrease in rho, thus increasing the ratio of S^(2)/rho on Ni substitution. At low T, the TEP shows an anomaly in the substituted samples, showing a peak at T ~ 20K.