A radioisotope piezoelectric generator (RPG) is a type of radioisotope generator that converts energy stored in

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

materials into motion, which is used to generate electricity using the repeated deformation of a

piezoelectric Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied stress (mechanics), mechanical s ...

material. This approach creates a high-impedance source and, unlike chemical batteries, the devices will work at a very wide range of temperatures.

History

In 2002 researchers at

Cornell University Cornell University is a Private university, private Ivy League research university based in Ithaca, New York, United States. The university was co-founded by American philanthropist Ezra Cornell and historian and educator Andrew Dickson W ...

published and patented the first design.

Mechanism

A piezoelectric cantilever is mounted directly above a base of the

radioactive isotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...

nickel-63. All of the radiation emitted as the millicurie-level nickel-63 thin film decays is in the form of

beta radiation A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus, known as beta decay. There are two forms of beta decay, β− decay and � ...

, which consists of

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

s. As the cantilever accumulates the emitted electrons, it builds up a negative charge at the same time that the isotope film becomes positively charged. The beta particles essentially transfer electronic charge from the

thin film A thin film is a layer of materials ranging from fractions of a nanometer ( monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ...

to the cantilever. The opposite charges cause the cantilever to bend toward the isotope film. Just as the cantilever touches the thin-film isotope, the charge jumps the gap. That permits current to flow back onto the isotope, equalizing the charge and resetting the cantilever. As long as the isotope is decaying - a process that can last for decades - the tiny cantilever will continue its up-and-down motion. As the cantilever directly generates electricity when deformed, a charge pulse is released each time the cantilever cycles. Radioactive isotopes can continue to release energy over periods ranging from weeks to decades. The half-life of nickel-63, for example, is over 100 years. Thus, a battery using this isotope might continue to supply useful energy for at least half that time. Researchers have demonstrated devices with about 7%

efficiency Efficiency is the often measurable ability to avoid making mistakes or wasting materials, energy, efforts, money, and time while performing a task. In a more general sense, it is the ability to do things well, successfully, and without waste. ...

with high frequencies of 120 Hz to low-frequency (every three hours) self-reciprocating actuators.

References

Nuclear technology Electric battery Electrical generators {{nuclear-tech-stub

History

Mechanism

See also

References