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Correlation of optical properties and temperature-induced irreversible phase transitions in europium-doped yttrium carbonate nanoparticles
Authors:Ray Gunawidjaja
Institution:Applied Sciences Laboratory, Institute for Shock Physics, Washington State University, Spokane, WA 99210-1495, USA
Abstract:Nanophase europium-doped yttrium carbonate precursors are subjected to heat treatments, ranging from 300 °C to 1100 °C for dwell times of 5 min, 30 min, and 180 min. XRD, TEM, FT-IR, fluorescence, fluorescence excitation, and fluorescence lifetime measurements are used to characterize the materials. Upon heating, the material transitions through several amorphous stages until it reaches the crystalline cubic Y2O3 phase. DSC measurements show an exothermic transition at 665.7 °C, indicating the formation of crystalline Y2O3. The grain size development is fitted by the relaxation equation and yields an activation energy of 50.3 kJ/mol. The amorphous phases are characterized by inhomogenously broadened optical spectra. Heating up to 700 °C leads to an increased fluorescence lifetime (from about 1 ms to 2.4 ms). As the material is heated to higher temperatures and completes the formation of the crystalline cubic Y2O3 phase, the optical spectra become narrower and the fluorescence lifetime decreases to about 1.2 ms.
Keywords:Thermometry  Europium-doped yttria  Nanoparticles  Structural changes  Optical properties
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