Thermoelectric materials allow the direct conversion of heat into electrical energy and vice versa, offering considerable potential for various technological applications.
A research team from the Vienna University of Technology (TU Wien) studied various metal alloys to identify thermoelectric materials with the most promising properties.
Their results, published in the prestigious journal Science Advances, reveal that the mixture of nickel and gold is especially interesting.
Applications of thermoelectric materials
The use of thermoelectric materials to generate electricity is not new. Since the mid 20’smy century, were used to produce electrical energy in space exploration. Thermoelectric materials also find applications in everyday life, such as in portable refrigerators.
Additionally, they could be used in industrial settings to convert waste heat into green electricity, to name just one of many potential applications.
How thermoelectricity works
The principle of thermoelectricity is based on the movement of charged particles that migrate from the warmer to the colder side of a material. This generates an electrical voltage, called thermoelectric voltage, which opposes the thermally excited motion of the charge carriers.
He Seebeck coefficient, named after German physicist Thomas Johann Seebeck, is an important parameter for evaluating the thermoelectric performance of a material. The key requirement is that there is an imbalance between the positive and negative charges, as they compensate for each other.
Nickel-gold alloys with exceptional properties
Physicists from the Institute of Solid State Physics (TU Wien) have managed to find metal alloys with high conductivity and exceptionally large Seebeck coefficient. Mixing the magnetic metal nickel with the noble metal gold radically changes the electronic properties. When the yellowish color of gold disappears with the addition of about 10% nickel, the thermoelectric performance increases rapidly.
The physical origin of this Seebeck effect The enhanced effect lies in the energy-dependent scattering behavior of electrons, a fundamentally different effect from that of semiconductor-based thermoelectrics.
A record material
The combination of extremely high electrical conductivity and a high Seebeck coefficient leads to record values of thermoelectric power factor in nickel-gold alloys, far exceeding those of conventional semiconductors.
“With the same geometry and a fixed temperature gradient, much more electrical energy could be generated than any other known material.“explains Fabian Garmroudi, first author of the study.
Additionally, the high power density could enable large-scale applications in the future. “With current features, smart watches, for example, could already be charged autonomously using the user’s body heat.“comments Andrej Pustogow, lead author of the study.
Nickel and gold are just the beginning
Although gold is an expensive element, this study represents a proof of concept.
“We were able to demonstrate that not only semiconductors, but also metals can exhibit good thermoelectric properties, making them relevant for various applications. Metal alloys have several advantages over semiconductors, especially in the manufacturing process of a thermoelectric generator.“explains Michael Parzer, one of the main authors of the study.
Before starting their experimental work, the researchers calculated, using theoretical models, which alloys were the most suitable. The group is also currently investigating other promising candidates that do not require the use of the expensive element gold.
Synthetic
Thermoelectric materials offer considerable potential for various technological applications. The study carried out by the research team at the Vienna University of Technology highlighted the exceptional thermoelectric properties of nickel-gold alloys. Although gold is an expensive element, this discovery opens the way to the search for other promising metal alloys for thermoelectric applications.
For a better understanding
Thermoelectricity is a phenomenon that allows the direct conversion of heat into electrical energy and vice versa. It is based on the movement of charged particles that migrate from the warmer to the colder side of a material, generating an electrical voltage called thermoelectric voltage. The Seebeck coefficient is an important parameter to evaluate the thermoelectric performance of a material.
2. What are the applications of thermoelectric materials?
Thermoelectric materials are used in a variety of applications, including electrical power generation in space exploration, portable refrigerators, and converting waste heat to green electricity in industrial settings.
3. What are the advantages of nickel-gold alloys?
Nickel-gold alloys exhibit extremely high electrical conductivity and a high Seebeck coefficient, leading to record values of thermoelectric power factor. This means that they can generate much more electrical energy than other known materials with the same geometry and a fixed temperature gradient.
4. Why is gold used in these alloys despite its high cost?
The use of gold in these alloys is a proof of concept demonstrating that metals can exhibit good thermoelectric properties. Researchers are currently studying other promising candidates that do not require the use of the expensive element gold.
5. What is the potential impact of this discovery?
The discovery of the exceptional thermoelectric properties of nickel-gold alloys could have a significant impact on the future development of sustainable and energy-efficient technologies, enabling the efficient conversion of heat to electricity and vice versa in various applications.
Main illustration legend: Diagram of the thermoelectric effect in nickel-gold alloys. – Credit: Fabián Garmroudi
Article: “High thermoelectric performance in NiAu metal alloys through interband dispersion” – DOI: 10.1126/sciadv.adj1611
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