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.
There are several mechanisms which have been proposed for the existence of colossal dielectric constant in the class of perovskite calcium copper titanate (CaCu<sub>3</sub>Ti<sub>4</sub>O<sub>12</sub> or CCTO) materials. Researches indicate that existence of twinning parallel to (100) (001) and (010) planes causes planar defects and causes changes in local electronic structure. This change can cause insulating barriers locally which contribute to the large dielectric values irrespective of processing. The combination of insulating barriers, defects and displacements caused by twinning have been attributed to the generation of large dielectric constant in CCTO. To examine some of these arguments some researchers replaced Ca with other elements and evaluated this concept. In this study we present the synthesis and characterization of Ga<sub>2/3</sub>Cu<sub>3</sub>Ti<sub>4</sub>O<sub>12-x</sub>N<sub>x</sub> (GCTON) material. This provides both distortion due to atomic size difference and defects due to insertion of nitrogen. The morphology of the compound was determined to show that processing has tremendous effect on the dielectric values. The resistivity of GCTON was several order higher than CCTO and dielectric constant was higher than 10,000.
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-NiO<sub>2</sub>), 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 MnO<sub>2</sub> (urea-NiO<sub>2</sub>-MnO<sub>2</sub>) on the morphology, processing and current voltage characteristics due to exposure of Cs-137 γ-radiation. It was observed that addition of MnO<sub>2</sub> in urea-NiO<sub>2</sub> composite decreases the sensitivity of detection. However, urea-NiO<sub>2</sub>-MnO<sub>2</sub> composite recovers to original properties after irradiation much faster than urea-NiO<sub>2</sub> composite.