Fabrication and Electrical Characterization of Uranyl-based Semiconductors

Highly dense pellets of U₃O₈ [uranyl urinate] and UO₃ [uranyl oxide] were fabricated to evaluate their possible use as solid state, direct conversion, semiconductor neutron detectors. By utilizing uranium oxide semiconductors, devices would not require a neutron moderating layer to first interact with neutrons, reducing the probability of reaction products failing to produce a signal in the semiconductor. In addition, fissile isotopes of uranium, such as ²³⁵U [uranium-235] have a high probability of undergoing fission when absorbing thermal neutrons, with resulting reaction products from neutron induced fission producing quantities of electron-hole pairs orders of magnitude more than produced by lighter high neutron cross-section isotopes such as ¹⁰B [boron-10] or ⁶Li [lithium-6]. This dissertation investigates the modification of electrical properties, such as electrical resistivity, by changing conditions of fabrication to include uniaxial pressing and heating to increase sintering as well as changes to composition by varying available oxygen. By use uniaxial hot pressing, electrical resistivity of uranyl oxide pellets was measured in the 10⁹-10¹¹ Ω-cm [ohm centimeter] range, orders-of-magnitude higher than previously reported values.

This work was supported by the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-15-1-0072, to the University of Tennessee institution. The contents do not necessarily reflect the position or the policy of the federal government, and no official endorsement should be inferred.