PHASE TRANSITIONS AND PHOTOLUMINESCENT PROPERTIES OF ANION-ENGINEERED Y2O3

Author

Maharram Jabrayilov, Louisiana State University and Agricultural and Mechanical CollegeFollow

Semester of Graduation

Fall 2022

Degree

Master of Science in Chemical Engineering (MSChE)

Department

The Gordon A. and Mary Cain Department of Chemical Engineering

Document Type

Thesis

Abstract

Rare earth doped metal oxides are widely employed as phosphor materials for white light LEDs (w-LEDs). The aim of this work is to engineer anionic sites of metal oxides, specifically, Y₂O₃, to investigate structural and luminescent properties relationships and energy transfer mechanisms between rare earth sensitizer and activator ions in different hosts.

A low temperature two-step hydrothermal/combustion method was employed to incorporate sulfate ions into Y₂O₃. Furthermore, annealing at 600 °C under H₂/N₂ was employed to convert Y₂O₂SO₄ to Y₂O₂S. XRD along with FTIR spectroscopy unveiled the formation of monoclinic and trigonal phase of Y₂O₂SO₄ and Y₂O₂S, respectively. Furthermore, Eu³⁺ was used to relate structural properties to luminescent properties due to the hypersensitivity of Eu³⁺ to the local environment and its coordination with ligand. PLE and PL measurements revealed a red shift of the charge transfer band and electric dipole transitions of Eu³⁺ due to different hybridization and optical electronegativities between rare earth ions and SO₄^2- and S^2- ions. Additionally, thermal stability analysis with TGA/DSC confirmed that Y₂O₂SO₄ transformed to Y₂O₂S starting at 600 °C and also some of the Y₂O₂SO₄ decomposed to Y₂O₃ at 800 °C under H₂/N₂ flow.

Ultimately, after revealing the structure-property relationships and phase transitions, Tb³⁺ and Tb³⁺/Ce³⁺ doping were used to identify the best host material for efficient energy transfer. Room temperature PL measurements and time-resolved spectroscopy at cryogenic temperature (77 K) showed that, Y₂O₂SO₄ is the most efficient host for realizing energy transfer from Ce³⁺ to Tb³⁺ to enhance green emission of Tb³⁺ ions owing to crystal field splitting of Ce³⁺ ions which occupied C₁ symmetry sites. Overall, this work gives an idea of the impact of anionic substitutions on structural and photoluminescent properties of metal oxides in order to design better performing phosphor materials for the application of w-LED devices.

Date

10-31-2022

Recommended Citation

Jabrayilov, Maharram, "PHASE TRANSITIONS AND PHOTOLUMINESCENT PROPERTIES OF ANION-ENGINEERED Y2O3" (2022). LSU Master's Theses. 5666.
https://repository.lsu.edu/gradschool_theses/5666

Committee Chair

Dr. Kerry M. Dooley

DOI

10.31390/gradschool_theses.5666