What is pyroelectricity?
Pyroelectricity is the measured change in net polarization proportional to a change in temperature in a material.
What materials are used in pyroelectrics?
The most common materials used are GaN, CsNo3, polyvinyl fluorides, derivatives of phenylpyridine, and cobalt phthalocyanine. Also, LiTaO3 is a crystal exhibiting both piezoelectric and pyroelectric properties, which has been used to create small-scale nuclear fusion.
How are pyroelectrics different than thermoelectrics?
Pyroelectrics generate charge through polarization of their atomic structure. Generally, the entire material is being heated and polarized simultaneously. This change in entropy generates free electrons, causing a current to flow. In thermoelectrics, a difference in heat between different parts of the thermoelectric material creates a potential difference (via the thermoelectric effect). This leads to a difference in applications as well. Both can be used to convert waste heat to electricity, but pyroelectrics would be fully exposed to such heat, while thermoelectrics need to be partially insulated against it to maintain a heat difference.
Project Descriptions
The residual thermal energy that is expelled from common applications, such as engines, is wasted because there is no easy way to use it. Although there has been much effort in developing thermoelectric based energy harvesters, these have always suffered from a low efficiency. One potential alternative technology for extracting useful electrical power from lower-temperature reservoirs is pyroelectric energy conversion.
In this technology the pyroelectric effect, the coupling between a materials electrical polarization and temperature, is harnessed. Placing the functional material in an oscillating thermal cycle while simultaneously switching the electric field applied to the material, it is driven through the so-called electric Ericsson/Olsen Cycle and useful work is extracted. In this project we consider the possibility of creating a pyroelectric energy harvester based on organic functional materials.