Access Type
Open Access Embargo
Date of Award
January 2024
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Chemistry
First Advisor
Federico A. Rabuffetti
Abstract
Luminescent temperature sensors offer unique advantages over thermocouples and pyrometers for applications in extreme environments such as operando wall temperature mapping of combustion engines. A refractory oxide host doped with an optically active ion has the potential to afford a thermosensitive phosphor with a well-defined temperature response in such extreme environments. However, the design of thermosensitive phosphors with targeted temperature sensitivity and spatial resolution in the operational temperature range of interest has been hindered by the inability to rationally select host–activator pairs. A major scientific question is what crystal-chemistry features a low thermal conductivity oxide must possess to afford a thermosensitive phosphor with targeted figures-of-merit. To begin addressing this question, there is a need for a materials platform in which structural, vibrational, and electronic features of the host can be compositionally tuned, as these are directly relevant for the luminescence response of the activator.This dissertation focuses on expanding the library of thermosensitive phosphors for high-temperature applications by including chemically tunable refractory oxide hosts Ba3MgTa2O9 (BMTO) and Y3NbO7 (YNO). Dy3+ has been selected as the activator given its relevance for thermometry at high temperatures. The core issue that this dissertation revolves around is establishing thermal quenching pathways of Dy3+-doped phosphors at high temperatures. Generating this understanding is significant to enable the rational design of high-temperature thermosensitive phosphors as thermal quenching directly correlates with the figures-of-merit of the sensor. We pursued four main objectives. (1) Optimization of solid-state routes to access phase pure BMTO and YNO, and chemically substituted (Dy,Ba,Sr)3MgTa2O9, (Dy,Y)3NbO7 analogs. (2) Analysis of the crystal structure of the target composition employing high-resolution structural probes. (3) Construction of a furnace with optical access ports to probe luminescence at high temperatures; and (4) study of the luminescence response of Dy3+-doped BMTO and YNO at high temperatures with an eye towards rationalizing active thermal quenching pathways.
Recommended Citation
Imer Rocha Pita, Marcos Ramon, "Thermosensitive Phosphors As Optical Temperature Sensors In Extreme Environments" (2024). Wayne State University Dissertations. 4053.
https://digitalcommons.wayne.edu/oa_dissertations/4053