Abstract

Phosphor thermometry is an increasingly popular method of making surface temperature measurements. The primary benefits of phosphor thermometry are that it does not require equipment to make contact with the surface and can be done remotely. This method uses a phosphor that exhibits one or more of the following changes with variations in temperature: change in decay time, change in relative intensities of emission peaks, or shifts in emission peak wavelengths. These changes with temperature are tested in a controlled setting to calibrate the phosphor for use.

Pyrochlores are a class of materials that follow the chemical structure A23+B24+O7 in which A and B can be a wide range of cations though they are generally rare earth elements or transition metals. Pyrochlores generally have low thermal conductivity allowing for their use in insulation materials for machinery such as turbines. When doped with rare earth elements such as europium, pyrochlores can act as thermographic phosphors making them useful for phosphor thermometry.

Previous research in this field has typically dealt with the thermal and material properties of these pyrochlores including: thermal conductivity, thermal expansion coefficient, fixed temperature spectroscopic properties. The purpose of this research project was to examine the temperature-dependent spectroscopic properties of three particular europium-doped pyrochlores in order to determine their suitability as thermographic phosphors. The pyrochlores tested included: La2Zr2O7:Eu, La2Hf2O7:Eu, and Nd2Zr2O7:Eu. The pyrochlores were synthesized using combustion synthesis at Vanderbilt University. The temperature-dependent spectroscopy was then done at Oak Ridge National Laboratory which had the necessary equipment. The change in emission decay times for these phosphors with changing temperature was measured. The ultimate goal was to determine the luminescent lifetime as a function of temperature for these materials.