In-plane Anisotropy on Resistivity and Thermopower in The Misfit Layered Oxide Bi2-xPbxSr2Co2Oy

TL;DR

This study explores the in-plane anisotropy in resistivity and thermopower of Bi2-xPbxSr2Co2Oy single crystals, revealing significant anisotropy and enhanced thermoelectric properties due to the misfit structure and Pb doping.

Contribution

It demonstrates how the misfit structure and Pb doping influence anisotropic electronic properties and thermoelectric performance in layered oxides.

Findings

Resistivity and thermopower anisotropy exceeds two.

Maximum thermopower at Pb doping level x=0.4.

High power factor of 9 μW/cmK^2 at 100 K for x=0.6.

Abstract

We investigated the in-plane anisotropy on the resistivity and thermopower of Bi2-xPbxSr2Co2Oy single crystals, which have a misfit structure between the hexagonal CoO2 layer and the rock salt Bi2Sr2O4 layer. The resistivity and thermopower show significantly large anisotropy, which exceeds two at maximum. This anisotropy would come from the anisotropic pseudogap formation enhanced by the misfit structure. The thermopower changes with Pb doping to take a maximum at x=0.4. The misfit structure improves the thermoelectric properties through chemical pressure. The power factor is as large as 9 muW/cmK2 at 100 K for x=0.6, which is the highest value for thermoelectric oxides at 100 K.