Patent Number: 052606210
Section: summary

FIELD OF THE INVENTION The present invention relates to radio-nuclide, voltaic-junction batteries, and, more particularly, to compact electric batteries that are powered by the combination of a nuclear radiation emitting source and a responsive semiconductor voltaic junction for service in many applications where chemical batteries are unsatisfactory or inferior. THE PRIOR ART Compact long-life energy sources have wide applications in such fields as aerospace systems, cardiac pacemakers, computer memory maintenance, remote instrumentation, etc. Chemical batteries suffer generally from theoretical limits in the energy density, they can accommodate. Radio-nuclide, voltaic-junction cells have much higher theoretical limits in energy density, in some cases more than a factor of 1000 greater, but, in the past, have not achieved desirable high energy density and long life in practice. A major problem in such prior art cells has been the limited ability of semiconductor junctions to withstand high energy alpha or beta emission without damage during operation. Silicon p-n junction cells for directly converting radiation, either visible or ionizing, to electricity were developed in the early 1950's. Specific use of radio-isotopes to power silicon p-n cells, known as betavoltaic cells, were extensively studied in the 1970's for applications where low power but high energy density were important, for example, in cardiac pacemakers. A primary motivation for these studies was that the theoretical energy density is much higher in betavoltaic cells than in the best chemical batteries, 24.3 W-h/cm.sup.3 versus 0.55 W-h/cm.sup.3 for mercury-zinc batteries. Unfortunately, isotopes that could be employed with silicon had to be limited to low energy beta emitters because of radiation damage. For example, threshold energy for electron damage is about 0.180 MeV assuming an atomic displacement damage threshold of 12.9 eV. Alpha particles cause so much damage that they were not seriously considered at any energy. This constraint excluded the most potent nuclide sources, and thus restricted maximum power of such devices because of limits to the specific activity achievable at maximum concentration with reasonable half-lives. BRIEF DESCRIPTION OF THE INVENTION The primary object of the present invention is to provide a novel high energy density electric cell comprising a nuclear source of relatively high energy radiation and concomitant heat, a semiconductor junction incorporating an inorganic crystalline compound of Group III and Group V elements characterized by defect generation in response to the nuclear source, and an enclosure having a sufficiently high thermal impedance to retain therewithin a sufficient quantity of the heat generated by the nuclear source for maintenance of the semiconductor junction above a predeterminedly high annealing temperature during operation. The nuclear radiation includes energetic radiation such as alpha, beta and gamma emissions or combinations thereof. The semiconductor junction, for example, includes compounds of indium and phosphorous differentially treated with n or p dopants. The thermal impedance is composed of a thermal insulator such as a ceramic electrical non-conductor. The arrangement is such that damage to the semiconductor junction resulting from the highly energetic emissions from the nuclear source is repaired by annealing in real time at the predetermined temperature maintained within the insulating enclosure. Other objects of the present invention will in part be obvious and will in part appear hereinafter.