Cu-Ni-Based Alloys from Nanopowders as Potent Thermoelectric Materials for High-Power Output Applications

Mario Wolf,Armin Feldhoff,Timon Steinhoff,Hans Jürgen Maier,Florian Nürnberger,Jan Flormann,Gregory Gerstein

doi:10.3390/alloys1010002

Abstract

A new approach for the development of thermoelectric materials, which focuses on a high-power factor instead of a large figure of merit zT, has drawn attention in recent years. In this context, the thermoelectric properties of Cu-Ni-based alloys with a very high electrical conductivity, a moderate Seebeck coefficient, and therefore a high power factor are presented as promising low-cost alternative materials for applications aiming to have a high electrical power output. The Cu-Ni-based alloys are prepared via an arc melting process of metallic nanopowders. The heavy elements tin and tungsten are chosen for alloying to further improve the power factor while simultaneously reducing the high thermal conductivity of the resulting metal alloy, which also has a positive effect on the zT value. Overall, the samples prepared with low amounts of Sn and W show an increase in the power factor and figure of merit zT compared to the pure Cu-Ni alloy. These results demonstrate the potential of these often overlooked metal alloys and the utilization of nanopowders for thermoelectric energy conversion.

Highlights

To achieve a sustainable electric power supply, the use of thermoelectric generators is a possible method to increase the energy efficiency in various applications by directly converting heat to electrical energy [1]
The performance of a thermoelectric material is defined by the three central thermoelectric quantities, namely, the Seebeck coefficient α, the electrical conductivity σ, and the open-circuited entropy conductivity Λ, which is related to the heat conductivity λ = T · Λ via the absolute temperature [3,4,5,6]
Cu-Ni-based metals alloyed with tin and tungsten were successfully produced via the arc melting of metal nanopowders

Summary

Introduction

To achieve a sustainable electric power supply, the use of thermoelectric generators is a possible method to increase the energy efficiency in various applications by directly converting heat (waste) to electrical energy [1]. Within the Ioffe plots, another promising material from the group of metal alloys can be identified, when a high power output is the main goal: Cu-Ni alloys This elemental combination has been widely used in thermoelements as constantan (Cu-Ni-Mn) due to its properties and stability at elevated temperatures. It is characterized simultaneously by a very high power factor up to 100 μW·cm−1 ·K−2 (see Figure 1a) and a high thermal conductivity, showing potential for high-temperature applications where power output may be more relevant than conversion efficiency [24,25]. The influence of the ut zation of nanopowders as well as the results of alloying with Sn and W are investigate

Materials and Methods

Results and Discussion

Normalized

Measured

Conclusions