The market for thermoelectric materials is forecast to grow at a CAGR of 27.3% through 2020.

Although the thermoelectric effect was discovered almost 200 years ago, thermoelectric materials have been experiencing strong renewed interest in recent years thanks to the development of advanced materials with increased thermoelectric efficiency and lower production costs.

Thermoelectric materials, which can be used for direct conversion of heat into electrical energy, or viceversa, are particularly appealing for energy harvesting applications. For example, these materials can be used to obtain power from the heat generated by combustion engines, manufacturing processes and equipment, or the human body.

A material’s thermoelectric efficiency is measured by the dimensionless factor (thermoelectric figure of merit) ZT = (σS²/k)T, where σ, S, k, and T are the electrical conductivity, the Seebeck coefficient (or thermoelectric power), the thermal conductivity, and the operating temperature, respectively. As a reference, bismuth telluride, a well-known thermoelectric material, has a ZT value of 1.0 at room temperature. However, bismuth telluride (Bi₂Te₃) has not gained widespread popularity primarily due to its high production cost.

To exhibit high thermoelectric efficiency, a material must be characterized by both high electrical conductivity and low thermal conductivity. Typically, those materials that have good electrical conductivity are also good thermal conductors. Advances in material science during the past ten years have led to the development of various formulations with relatively high ZT values. They are summarized in the table below.

At the indicated temperature, the ZT value for that particular material reaches the reported peak value. Materials with ZT values equal to or greater than 1 are attracting particular interest; although, in an effort to make thermoelectricity more competitive with alternative technologies, the objective of current research is to obtain ZT values closer to 3.

In April 2014, Nature reported that scientists at Northwestern University (Evanston, IL) and the University of Michigan (Ann Arbor, MI) discovered a ZT value of 2.6 at 923 K in SnSe single crystals along the b axis of the room-temperature orthorhombic unit cell.

 Thermoelectric materials with high ZT values.

    Source: AMG NewTech

The global market for thermoelectric materials is currently very small and estimated to reach $3 million in 2015, but it is forecast to grow at a rapid CAGR of 27.3% during the next five years.

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Keywords: thermoelectric, heat to electricity, conversion, materials, market