Session: MNS-01 MEMS/NEMS Power Sources, Sensors and Actuators, and Computing

Paper Number: 69835

Start Time: August 17, 11:10 AM

69835 - Demonstration of a Radioisotope Power Source Using Promethium-147 Chloride and 4H-SiC Betavoltaic Cell 

Unattended  compact, terrestrial and space sensors require power sources that have high energy and power density to continuously operate for 3 to 25 years depending on application. Currently, chemical sources cannot fully satisfy these conditions. Radioisotope power sources using β^--emitting radioisotopes have energy densities 1000× greater than chemical sources. Their power density is a function of β- flux saturation in the planar (2D) configuration, β^- emission range in the semiconductor converter, and betavoltaic (βV) or beta-photovoltaic (β-PV) cell geometry. Using state-of-the-art (SOA) 4H-SiC βV cell and 2D configuration, promethium-147 (¹⁴⁷Pm) is the only β^--emitting radioisotope that can match power density with chemical sources while surpassing them in energy density. This approach to match power density while sustaining the unmatchable energy density is described. Promethium-147(III)  chloride (¹⁴⁷PmCl₃) and 4H-SiC βV cell were used for the 2D configuration, nuclear power source. The ¹⁴⁷PmCl₃ dried layers were sensitive to laboratory air moisture. The dried layers absorbed the external moisture and lowered the maximum power point (MPP) of the βV cell. Moisture controllability through continuous heating during dispensing and placement in airtight enclosures during I-V curve measurements lessened the moisture absorption negative effects shown by increasing MPP. A total activity of 1,680 mCi/cm² was deposited on a 4H-SiC βV cell. A MPP of ≈3.2 µW/cm² was generated after source drying period. MPP saturation point was not reached at 1,680 mCi/cm². This extrapolates to ≈6.4 µW/cm² of ¹⁴⁷PmCl₃ in between 2× 4H-SiC making a battery packet and ≈64 µW/cm³ with 10× packets at 1 cm². At this power density, the nuclear power source could supply milliwatts to various sensors for at least 3 years continuously in a 1000 cm³ total volume.

Presenting Author: marc litz Army Research Laboratory

Authors:

Johnny Russo University of Maryland
Marc Litz U.S. Army Research Laboratory
Brenda Smith Oak Ridge National Laboratory