Over the last few years, researchers at the Christian Doppler Laboratory for Thermoelectricity have been studying different thermoelectric materials for different applications. This research has now led to the discovery of a remarkable thermoelectric material that the researchers claim to be the most effective ever created in converting heat into electrical energy.
This is an unprecedented ability and means that a lot of hope is being pinned on it, with some commentators speculating that it could be used to provide an autonomous and renewable energy source for a range of power-efficient technologies such as sensors and small processors, allowing them to generate their own energy.
Professor Ernst Bauer working in his lab. Image Credit: TU Wien.
A New Thermoelectric Material
Thermoelectric materials are those that can convert heat into electrical energy, something that is known as the Seebeck effect: if there is a difference in temperature between two ends of one material, an electrical voltage can be generated, and current can start to flow.
The amount of electrical energy that can be generated at a given temperature difference is measured using the ZT value. The higher this is, the better the material’s thermoelectric properties.
To date, the best thermoelectric materials have been measured at around 2.5 to 2.8 ZT. This has now been beaten by Austrian researchers at TU Wien in Vienna. They have developed a completely new material with a ZT value of between 5 and 6. The material is composed of a thin layer of iron, vanadium, tungsten, and aluminum applied to a silicon crystal.
Professor Ernst Bauer from the Institute of Solid State Physics at TU Wien said that a good thermoelectric material must have a strong Seebeck effect while also meeting two requirements that are difficult to bring together, that "On the one hand, it should conduct electricity as well as possible; on the other hand, it should transport heat as poorly as possible. This is a challenge because electrical conductivity and thermal conductivity are usually closely related."
How It Works
Core to the thermal conductivity of the new material is its “combination of several physical properties and parameters”, according to Bauer.
Atoms in the material are arranged in a face-centered cubic lattice. The distance between the two iron atoms is always the same, as is the distance between the atoms that comprise the other elements found in the material.
However, when a thin layer of the material is applied to silicon, there is a change in its structure. While the atoms still form a cubic pattern, they form in a way where the distribution of the different types of atom becomes randomized.
This change in atomic arrangement changes the material’s electronic structure which protects the electrical charge as it moves through the material. This results in a very low electrical resistance.
Although a thin layer of the material alone cannot generate enough energy to power even the smallest of devices, it is very compact and adaptable. The new material is so effective, in fact, that it could be used to provide energy for sensors and small computer processors. Instead of connecting devices to cables, they could generate their own electricity from temperature differences.
The Austrian researchers aim to develop the material and use it as a component of small-scale energy generators to provide power for sensors and other small electronic devices.