Development of New Inorganic Luminescent Materials by Organic-Metal Complex Route
AdvisorLaCombe, Jeffrey C.
Chemical and Materials Engineering
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<bold>Abstract</bold>The development of novel inorganic luminescent materials has provided important improvements in lighting, display, and other technologically-important optical devices. The optical characteristics of inorganic luminescent materials (phosphors) depend on their physicochemical characteristics, including the atomic structure, homogeneity in composition, microstructure, defects, and interfaces which are all controlled by thermodynamics and kinetics of synthesis from various raw materials. A large variety of technologically-important phosphors have been produced using conventional high-temperature solid-state methods. For the synthesis of functional ceramic materials with ionic dopants in a host lattice, (such as phosphors), synthesis using organic-metal complex methods and other wet chemistry routes have been found to be excellent techniques. These methods have inherent advantages such as good control of stoichiometry by molecular level of mixing, product homogeneity, simpler synthesis procedures, and use of relatively-low calcination temperatures. Supporting evidence for this claim is accomplished by a comparison of photoluminescence characteristics of a commercially available green phosphor, Zn<sub>2</sub>SiO<sub>4</sub>:Mn, with the same material system synthesized by organic-metal synthesis route.In this study, new inorganic luminescent materials were produced using rare-earth elements (Eu<super>3+</super>, Ce<super>3+</super>, Tb<super>3+</super>) and transition metals (Cu<super>+</super>, Pb<super>2+</super>) as dopants within the crystalline host lattices; SrZnO<sub>2</sub>, Ba<sub>2</sub>YAlO<sub>5</sub>, M<sub>3</sub>Al<sub>2</sub>O<sub>6</sub> (M=Ca,Sr,Ba). These novel phosphors were prepared using the organic-metal complex route. Polyvinyl alcohol, sucrose, and adipic acid were used as the organic component to prepare the ceramic precursors. Materials characterization of the synthesized precursor powders and calcined phosphor samples was performed using X-Ray Diffraction, Scanning Electron Microscopy, Photon-Correlation spectroscopy, and Fourier Transform Infrared Spectroscopy techniques. In addition to the Fluorescence Spectrometer, and Diffuse Reflectance Spectroscopy, the Time Resolved Spectroscopy technique was also used to study the photoluminescence characteristics of the synthesized phosphors. Using these characterization techniques, and through careful comparisons with related studies in the literature, the mechanisms of luminescence for each of the new phosphor materials synthesized here was discussed in a detail.