TRITIATED NITROXIDE FOR BETAVOLTAIC CELL NUCLEAR BATTERY: 3D BETA FLUX MODELING, SYNTHESIS, STABILITY ANALYSIS, AND COATING TECHNIQUES

Abstract

Beta (β-) radioisotope energy sources, such as tritium (3H), have shown significant potential in satisfying the needs of a sensor-driven world. The limitations of current β- sources include: (i) low beta-flux power, (ii) intrinsic isotope leakage (instability) and (iii) beta self-absorption. The figure of merit is the β--flux power (dPβ/dS), where an optimal portion of incident beta particles penetrates the semiconductor depletion region. The goal of this research was to identify a compound to contain a beta emitter that can permit beta-flux power of at least 733nW/cm2 from one side, where it can be used for both planar and high aspect ratio microstructure technology (HARMST) transducers. Nitroxides were chosen because of previous demonstrated deuteration, ease of synthesis, diversity of structure, and pliability. A 6-membered nitroxide was prepared and tritiated with a specific activity of 103Ci/g. The product was stable after 256 days with only 2% tritium loss. A betavoltaic (βV) cell nuclear battery prototype was demonstrated with the tritiation of a 5-membered nitroxide stable in liquid and solid form and a specific activity (Am) of 635Ci/g, the highest recorded Am for an organic compound. A dPβ/dS of 51 nW/cm2 and 102 nW/cm2 were generated when dispensed on βV (4H-SiC) and PV (InGaP) cells. Improvements to increase the dPβ/dS closer to the theoretical limit were identified and demonstrated such as dispensing with different solvents to reduce evaporation time, and increasing solute (nitroxide) concentration in the dispensed solution. A βV cell nuclear battery model was developed, producing a blueprint on what nitroxide characteristics are required to maximize the dPβ/dS and electrical power density (P_(e,vol)). The percent error and percent difference were less than 6% compared to experimental data and other models. For the planar coupling configuration, increasing Am while increasing mass density increases P_(e,vol). Increasing the surface area interaction with the radioisotope and transducer increases the volume radioactivity (Vm), but does not always generate a higher β- source efficiency nor P_(e,vol) compared to the planar coupling configuration. The rectangular pillar array produced the highest 4.54 mW/cm3 of at the highest Vm where HARMST feature width and gaps are proportionally minimized at 100 nm wide.