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Cerium doped elpasolite halide scintillators

Doty, F.P.; Zhou, Xiaowang; Noda, Frank T.

Low-cost, high-performance gamma-ray spectrometers are urgently needed for proliferation detection and homeland security. The cost and availability of large scintillators used in the spectrometer generally hinge on their mechanical property and crystal symmetry. Low symmetry, intrinsically brittle crystals, such as these emerging lanthanide halide scintillators, are particularly difficult to grow in large sizes due to the development of large anisotropic thermomechanical stresses during solidification process. Isotropic cubic scintillators, such as alkali halides, while affordable and can be produced in large sizes, are poor spectrometers due to severe nonproportional response and modest light yield. This work investigates and compares four new elpasolite based lanthanide halides, including Cs2LiLaBr6, Cs2NaLaBr6, Cs2LiLaI6, and Cs2NaLaI6, in terms of their crystal symmetry, characteristics of photoluminescence and optical quantum efficiency. The mechanical property and thermal expansion behavior of the cubic Cs2LiLaBr6 will be reported. The isotropic nature of this material has potential for scaled-up crystal growth, as well as the possibility of low-cost polycrystalline ceramic processing. In addition, the proportional response with gamma-ray energy of directionally solidified Cs2LiLaBr6 will be compared with workhorse alkali halide scintillators. The processing challenges associated with hot forged polycrystalline elpasolite based lanthanide halides will also be discussed.

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TYPE Conference YEAR 2010
OSTI

Understanding Li-ion battery processes at the atomic to nano-scale

Huang, Jian Y.; Subramanian, Arunkumar; Hudak, Nicholas S.

Reducing battery materials to nano-scale dimensions may improve battery performance while maintaining the use of low-cost materials. However, we need better characterization tools with atomic to nano-scale resolution in order to understand degradation mechanisms and the structural and mechanical changes that occur in these new materials during battery cycling. To meet this need, we have developed a micro-electromechanical systems (MEMS)-based platform for performing electrochemical measurements using volatile electrolytes inside a transmission electron microscope (TEM). This platform uses flip-chip assembly with special alignment features and multiple buried electrode configurations. In addition to this platform, we have developed an unsealed platform that permits in situ TEM electrochemistry using ionic liquid electrolytes. As a test of these platform concepts, we have assembled MnO{sub 2} nanowires on to the platform using dielectrophoresis and have examined their electrical and structural changes as a function of lithiation. These results reveal a large irreversible drop in electronic conductance and the creation of a high degree of lattice disorder following lithiation of the nanowires. From these initial results, we conclude that the future full development of in situ TEM characterization tools will enable important mechanistic understanding of Li-ion battery materials.

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TYPE Conference YEAR 2010
OSTI
Results 73376–73400 of 99,299
Results 73376–73400 of 99,299