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Why are most materials not thermoelectrically strong enough? The truth is revealed!
As energy conversion technology receives increasing attention today, thermoelectric materials have become the focus of research. These materials can convert thermal energy into electrical energy and vice versa, offering potential applications in energy recovery and cooling systems. However, why do the thermoelectric effects of most materials still fail to meet the needs of practical applications? This article will reveal the truth, as well as the current challenges and development directions of thermoelectric materials.
The thermoelectric effect refers to the phenomenon in which temperature differences produce potential differences or currents produce temperature differences.
Basic concepts of thermoelectric effect
The thermoelectric effect covers three main phenomena: Seebeck effect, Peltier effect and Thomson effect. The application of these three effects greatly expands the possibilities of energy conversion. However, although all materials have a non-zero thermoelectric effect, the effect is too small for most to be useful in practical applications.
Advantages and uses of thermoelectric materials
Currently the most commonly used thermoelectric material is an alloy based on antimony telluride (Bi2Te3), which excels in niche applications such as cooling and energy recovery. With the in-depth research on thermoelectric materials, it has been found that efficient thermoelectric materials need to have three basic conditions: high electrical conductivity, low thermal conductivity and high Seebeck coefficient.
Material efficiency challenges: The trade-off between thermal conductivity and electrical conductivity
When exploring thermoelectric materials, a key challenge is the competition between electrical and thermal conductivity. According to the Widmann-Franz law, an increase in electrical conductivity is usually accompanied by an increase in thermal conductivity, which makes it difficult for the thermoelectric effect of the material to reach an ideal state. Current research focuses on how to optimize these properties to improve the thermoelectric figure of merit (Z) of the material.
In order to improve the thermoelectric properties of materials, researchers have explored the possibility of new materials such as alloys, complex crystals and nanocomposites.
Device efficiency and thermoelectric effect
The efficiency of a thermoelectric device depends on the material's properties at a specific temperature, including electrical conductivity, thermal conductivity, and Seebeck coefficient. In actual devices, a combination of n-type and p-type materials is usually used, which further increases the complexity of the system. Ideally, the properties of both materials should remain stable over the same temperature range, but this is often not the case.
Quality factor of thermoelectric materials
The quality factor of a material reflects its potential efficiency. Researchers are trying to improve thermoelectric conversion efficiency by increasing the state density of electrons and reducing the lattice thermal conductivity. This process requires the material to behave as a crystal during electron transmission and glassy during phonon transmission, a concept known as "phonon glass electronic crystals."
Future research directions
With the advancement of science and technology, the development of thermoelectric materials continues to move towards advanced conventional materials and low-dimensional systems. The potential of these materials to reduce lattice thermal conductivity makes them key to future thermoelectric systems. In the process of exploring new materials, scientists will also consider how to achieve higher efficiency and stability in various possible applications.
"Whether it is from basic research or specific application levels, the potential of thermoelectric materials is still worthy of further exploration."
Although thermoelectric materials have shown their importance in current technology, they still face multiple challenges. What makes people curious is, can future technological innovation break through these limitations and improve the practicality and economy of thermoelectric materials?
