Alternative materials for radiovoltaics
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] This work explores alternative materials for the improvement of radiovoltaic devices. First, lithium fluoride is explored as an effective material for generating and retaining tritium radionuclides for use in radiovoltaics. This development aims to solve a decades-old problem of inadequate tritium hosts, which have been consistently limited in their ability to retain the radioisotope and effectively deliver energy to transducing semiconductors. This new method of tritium production and retention offers new possibilities for use of what has been deemed the safest radioisotope, and offers a simple, rapid production process, which can greatly reduce cumbersome isotope loading processes associated with existing methods of fabrication for devices reliant on tritium or other radioisotopes. The primary focus of this work is the exploration of molten selenium-sulfur as a radiation-resistant semiconductor for radiovoltaic devices. Radiovoltaics have thus far been unable to utilize high energy alpha and beta radiation due to rapid performance degradation imposed by radiation damage. This work includes the exhibition of long-term power output from an alphavoltaic device fueled by 210Po. The 57+ day lifetime of this device is in great contrast to reports of conventional semiconductors, which have consistently exhibited short lifetimes. Moreover, this report details a neutron diffraction study of irradiated Se-S material, which indicates strong radiation-resistance in the liquid phase. With liquid selenium established as a promising material for radiovoltaics, this work also presents a neutron diffraction study on the material's atomic structure, which has been the subject of dispute in published literature. The neutron diffraction study is accompanied by Reverse Monte Carlo analysis, resulting in reliable conclusions regarding the overall structure near the melting point. The analysis of Reverse Monte Carlo models in comparison to experimental data identifies in the pair correlation function a key indicator of 3-fold coordinated defects which disrupt the liquid selenium structure under extreme conditions.
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