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Access Type

WSU Access

Date of Award

January 2019

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Chemistry

First Advisor

Federico A. Rabuffetti

Abstract

ABSTRACT

RARE-EARTH-ACTIVATED GROUP VI d0 METAL OXIDES AS

THERMOSENSITIVE PHOSPHORS

by

SAMARAGE SAMEERA PRASAD PERERA

AUGUST 2019

Advisor: Dr. Federico A. Rabuffetti

Major: Chemistry

Degree: Doctor of Philosophy

Thermosensitive phosphors are solid-state materials that demonstrate distinct dependence of luminescence emission on temperature. These materials enable optical temperature sensing in environments where conventional thermometry is not possible (e.g., gas turbines, combustion engines, surface temperature distributions). However, the design of thermosensitive phosphors that show adequate sensitivity and low thermal quenching in the intermediate temperature range (i.e., 500–1000 K) remains challenging. This challenge can be addressed by understanding how to rationally manipulate the phosphor’s chemical composition and the crystal structure to tailor their thermometric response. With the aim of bridging this knowledge gap, this dissertation presents an investigation of the temperature-dependent luminescence response of a series of chemically and structurally tunable phosphors. Solid-state synthesis, structural characterization, and temperature-dependent luminescence response of rare-earth-activated scheelite and scheelite-related phosphors are presented to this end. Thermometric response of a series of Dy3+-activated NaLa(MO4)2 and Na5La(MO4)4 single-emitter phosphors in 300–700 K temperature range was investigated. Their potential as thermosensitive phosphors were revealed. Dual-emitter phosphors featuring two rare-earth ions with different thermal quenching characteristics were developed. Upon investigating their thermometric response, the advantage of using dual-emitter phosphors over single-emitter phosphors to overcome the effect of thermal quenching on relative sensitivity was revealed. Finally, the importance of coupling rare-earth and transition metal ions to develop dual-emitter phosphors to improve the thermometric sensitivity and exploring new host for thermosensitive phosphors was highlighted.

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