High-Performance Transparent Optical Ceramic Scintillators through Nanotechnology

描述(申请人提供)：LSO被公认为是理想的PET闪烁体。它对511keV伽马射线具有很强的阻挡能力，光产额超过20000光子/MeV，快速衰变32 ns。它实现了高符合时间分辨率和能量分辨率。但LSO单晶生长困难，成本高，重复性差，材料根本无法用于一般商业用途。为了克服这些缺点，我们在以前的工作中开发了一种半透明的LSO光学陶瓷，它具有与单晶相当的闪烁性能，而且更容易制备，可以以更低的成本填补可获得性空白。但由于LSO是光学各向异性的，传统的陶瓷技术不能使其完全透明。然而，最近，通过纳米技术开发了一种新的工艺，即使是光学各向异性材料，也能够在陶瓷中实现几乎完全透明。这项技术涉及在将最终颗粒尺寸限制在可见光波长以下的条件下对纳米粉末进行固结，从而防止几乎所有的散射并使材料完全透明。这种方法已经在多晶氧化铝的实验中得到了完全证实，这种多晶氧化铝同样是各向异性的，并且正在开发用于光学窗口的应用。这项提议的目的是将这两种已经开发的技术结合起来，以产生全透明光学陶瓷的形式，其闪烁性能与单晶相当。在第一阶段，我们将确认已经为氧化铝建立的工艺也适用于LSO。我们将建立制造所需纳米颗粒粉末的技术，并确定能够实现所需材料性能的固结条件。

DESCRIPTION (provided by applicant): LSO is generally recognized as the ideal scintillator for PET. It has high stopping power for 511 keV gamma rays, high light yield of over 20000 photons/MeV, and rapid decay of 32 ns. It achieves high coincidence timing resolution and energy resolution. But single crystals of LSO are difficult and expensive to grow, reproducibility is poor, and the material is simply not available for general commercial use. To overcome these drawbacks, we have in our previous work developed a translucent LSO optical ceramic, which displays scintillation performance comparable to that of the single crystal, yet is easier to fabricate and could fill the availability gap at lower cost. But because LSO is optically anisotropic, it cannot be made fully transparent by conventional ceramic technology. Recently, however, a new process has been developed through nanotechnology that is capable of achieving virtually full transparency in ceramics of even optically anisotropic materials. The technique involves the consolidation of nanopowders under conditions that limit the ultimate grain sizes to below the wavelengths of visible light, thereby preventing virtually all scattering and rendering the material fully transparent. The procedure has been completely confirmed in experiments on polycrystalline alumina, which is similarly anisotropic, and is being developed for optical window applications. It is the aim of this proposal to combine the two already developed technologies so as to produce LSO in the form of a fully transparent optical ceramic, which displays scintillation performance comparable to that of a single crystal. In Phase I we will confirm that the process that has already been established for alumina is adaptable to LSO as well. We will establish techniques to fabricate the necessary nanoparticulate powders and to define the consolidation conditions under which the desired material properties can be achieved.