Atomic battery
[4] Since RCA's initial research and development in the early 1950s, many types and methods have been designed to extract electrical energy from nuclear sources.
The scientific principles are well known, but modern nano-scale technology and new wide-bandgap semiconductors have allowed the making of new devices and interesting material properties not previously available.
The non-thermal converters, such as betavoltaic cells, extract energy directly from the emitted radiation, before it is degraded into heat; they are easier to miniaturize and do not need a thermal gradient to operate, so they can be used in small machines.
Caesium vapor is used to optimize the electrode work functions and provide an ion supply (by surface ionization) to neutralize the electron space charge.
However, the carrier density and charge can be adjusted in semiconductor materials such as bismuth telluride and silicon germanium to achieve much higher conversion efficiencies.
A more efficient version, the advanced Stirling radioisotope generator, was under development by NASA, but was cancelled in 2013 due to large-scale cost overruns.
Moseley's apparatus consisted of a glass globe silvered on the inside with a radium emitter mounted on the tip of a wire at the center.
As late as 1945 the Moseley model guided other efforts to build experimental batteries generating electricity from the emissions of radioactive elements.
Depending on the type of radiation targeted, these devices are called alphavoltaic (AV, αV), betavoltaic (BV, βV) and/or gammavoltaic (GV, γV).
Betavoltaics have traditionally received the most attention since (low-energy) beta emitters cause the least amount of radiative damage, thus allowing a longer operating life and less shielding.
[15][16] Gammavoltaic devices use a semiconductor junction to produce electrical energy from energetic gamma particles (high-energy photons).
[17] Another patented design involves scattering of the gamma particle until its energy has decreased enough to be absorbed in a conventional photovoltaic cell.
[25] Medtronic and Alcatel developed a plutonium-powered pacemaker, the Numec NU-5, powered by a 2.5 Ci slug of plutonium 238, first implanted in a human patient in 1970.
Strontium-90 is easily extracted from spent nuclear fuel but must be converted into the perovskite form strontium titanate to reduce its chemical mobility, cutting power density in half.
Caesium-137, another high yield nuclear fission product, is rarely used in atomic batteries because it is difficult to convert into chemically inert substances.
Another undesirable property of Cs-137 extracted from spent nuclear fuel is that it is contaminated with other isotopes of Caesium which reduce power density further.
Ongoing work demonstrate that this cantilever is capable of radio frequency transmission, allowing MEMS devices to communicate with one another wirelessly.
