Synthesis and crystal growth of scintillators and semiconductor materials for radiation detectors have been proven to be time consuming and very costly. Several alternative crystals such as Tl3ASSe3, TlGaSe2, Tl4HgI6, PbSe(1-x)Ix have developed in our laboratory. These heavy metal and high Z based compounds have shown great promise. We have been working on some innovative approaches based on Cerenkov radiation and nanocomposites of ionizing organics for faster and efficient sensors. By combining some metallic oxides with an organic material, it should be possible to both extend the energy range of particles capable of being detected while also providing more discrimination for high energy gamma-rays, based on local secondary effects in the surrounding organic matrix. We have been working with a highly ionizing organic compound p-chloranil (2,3,5,6-Tetrachloro-1,4-benzoquinone) matrix. In addition, we have determined effect of oxidizing compounds MnO2 on urea-based composites. We use metal oxide as active ingredient in this matrix. We will present effect of morphology and processing on the performance of nanocomposite for sensing gamma-rays.
The transition metal oxide embodied organic composites have great promise for high energy radiation detection. The interaction of high energy radiation such as γ-rays with the organic composite can generate photoelectric responses, Compton scattering and electron hole pairs, which can provide favorable properties to enhance the radiation detectivity of the composite. These effects along with changes of oxidation state of metal oxides, provide significant change in the electrical characteristics of composites due to radiation exposure. We have developed nickel oxide (NiO2) nanoparticles embodied urea composite (urea-NiO2), and determined effect of γ-radiation on the current – voltage characteristics in the frequency range of 100 Hz to 100,000Hz. In this paper, we describe the results of effect of additional oxidizing agent MnO2 (urea-NiO2-MnO2) on the morphology, processing and current voltage characteristics due to exposure of Cs-137 γ-radiation. It was observed that addition of MnO2 in urea-NiO2 composite decreases the sensitivity of detection. However, urea-NiO2-MnO2 composite recovers to original properties after irradiation much faster than urea-NiO2 composite.
Thin film and nanocrystalline materials of oxides have been very attractive choice as low cost option for γ-ray
detection and have shown great promise. Our studies on pure oxide films indicated that thickness and microstructure
have pronounced effect on sensitivity. Since the interaction of γ-ray with composites involves all three interaction
processes; photoelectric effect, Compton scattering, and pair production, composites containing ionic organics have
better chance for enhancing sensitivity. In the composites of ionizing organics oxidation effect of unusual oxides
changes much faster and hence increases the sensitivity of radiation. In this study, we have used nickel oxide and
titanium oxide in ionic organics to develop composite materials for low energy γ-ray sensing. We prepared
composites containing ethylene carbonate and evaluated the effect of commercial Cs-137 radiation source by
studying current-voltage relationship at several frequencies. Radiated samples showed higher resistivity compared to
as prepared composites.
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