Improving the thermoelectric performance in Mg3+xSb1.5Bi0.49Te0.01 by reducing excess Mg

Kazuki Imasato,G Jeffrey Snyder,Stephen Dongmin Kang,Saneyuki Ohno

doi:10.1063/1.5011379

Kazuki Imasato, G Jeffrey Snyder + Show 2 more

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https://doi.org/10.1063/1.5011379

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Abstract

The thermoelectric performance of Mg3+xSb1.5Bi0.49Te0.01 was improved by reducing the amount of excess Mg (x = 0.01-0.2). A 20% reduction in effective lattice thermal conductivity at 600 K was observed by decreasing the nominal x from 0.2 to 0.01 in Mg3+xSb1.5Bi0.49Te0.01, leading to a 20% improvement in the figure-of-merit zT. Since materials with different amounts of Mg have similar electronic properties, the enhancement is attributed primarily to the reduction in thermal conductivity. It is known that excess Mg is required to make n-type Mg3+xSb1.5Bi0.49Te0.01; however, too much excess Mg in the material increases the thermal conductivity and is therefore detrimental for the overall thermoelectric performance of the material.

Highlights

Thermoelectric materials that can generate electricity directly from waste heat have attracted attention because of the large demand of higher fuel efficiency and environment-friendly technology.[1,2] The maximum performance of thermoelectric materials is evaluated by its figure-of-merit zT
Beyond an excess Mg of x > 0.01 in our synthesis, we find that samples have increasingly higher thermal conductivity presumably due to impurities
We reveal that this excess elemental Mg above the minimal threshold is detrimental to the thermoelectric performance and that minimization of this excess Mg increases the thermoelectric performance of Mg3+ x Sb1.5 Bi0.49 Te0.01

Summary

Introduction

Thermoelectric materials that can generate electricity directly from waste heat have attracted attention because of the large demand of higher fuel efficiency and environment-friendly technology.[1,2] The maximum performance of thermoelectric materials is evaluated by its figure-of-merit zT. One strategy for the improvement of thermoelectric property is to make κl comparable to the glassy limit of lattice thermal conductivity κmin.[3,4,5] We find that the figure-of-merit is 1.2 times higher at 600 K in the sample with reduced nominal x (Mg3+xSb1.5Bi0.49Te0.01) due to the reduction in thermal conductivity.

Results

Conclusion