Temperature, Stress and Microstructural Influences on the Luminescence Properties of Rare Earth Activated Yttrium Oxide

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9972509McKittrickPhotoluminescence is the process by which photons (infrared , visible, ultraviolet [UV]) are emitted from a solid under excitation by higher energy photons. Rare earth activated oxides (e.g., europium-doped yttrium oxide are a class of solids that emit visible light when bombarded with UV photons. These materials have application in information displays, lighting, and scintillators. The luminescence emission intensity, spectral energy distribution (intensity as a function of wavelength), and luminescence decay rate are influenced by the application of temperature or stress. Previous work on quantifying these effects has been done almost exclusively on single crystals. Technologically important materials, such as polycrystalline thin-films, have not been examined. A better understanding of the effect of external influences on the luminescence properties of thin- films is necessary for these materials to have more wide-spread industrial use. The objective of this project is twofold: (1) determine the applicability of theoretically predicted luminescence behavior to experimental values obtained on rare earth doped yttrium oxide single crystals or polycrystalline compacts as a function of temperature and stress and to (2) identify and quantify the temperature, stress and microstructure dependent luminescence properties of thin-films and compare these values to what was obtained previously. In the research, luminescence property data on single crystals of rare earth activated yttrium oxide (and/or polycrystalline yttrium oxide as a function of temperature and stress wil be obtained and compared with the currently available fundamental equations predicting the behavior; thin-films will be fabricated and the luminescence properties examined as compared with the single crystal data as a function of temperature and stress; the effect of grain boundary density, dislocation density, segregation of activators and grain size on the thin-film luminescence properties will be quantified; and a model and predictive relationships will be provided that are based on the fundamental equations that include the effect of temperature, microstructural features and residual stress on the luminescence properties of thin-film rare earth activated yttrium oxide. %%%Luminescent solids are used in many consumer applications, the most well known of these is as phosphors for computer display screens. This project will examine and try to understand the behavior of one class of these materials in order to increase the efficiently and thus decrease the cost of the materials. The project will be carried out by two researchers, one an expert in luminescent materials and one an expert in mechanical properties.***