Date of Award

5-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Materials Science and Engineering

Committee Member

Dr. Luiz G. Jacobsohn

Committee Member

Dr. Timothy A. DeVol

Committee Member

Dr. Fei Peng

Abstract

(Lu1-xPrx)3Al5O12 (LuAG:Pr) is seen as a promising scintillator for positron emission tomography (PET) scanners due to its high density and fast scintillation decay time. However, the high temperatures needed to grow single crystals and limitations in the incorporation of Pr into LuAG crystals make transparent ceramics of this material an attractive alternative. In this work, (Lu1-xPrx)3Al5O12 powders and ceramic bodies with different Pr concentrations, from x = 0.0001 to x = 0.05 were fabricated and characterized. The luminescence concentration quenching of LuAG:Pr powders and ceramic bodies was estimated by means of photoluminescence measurements. The powders show maximum photoluminescence intensity at dopant concentration of 0.18-0.33 at.%. Sintering of the pressed powder compacts at 1500°C for 20hrs in air produced a substantial increase in luminescence intensity along with a shift of the maximum photoluminescence emission intensity to lower concentrations between 0.018 and 0.18 at. % Pr. For ceramics sintered for short sintering times up to about 3-5hrs, it was determined that photoluminescence emission intensity is maximized for Pr concentrations of about 0.33 at. %. For a single Pr concentration of 0.18 at.%, the fabrication of LuAG:Pr ceramic bodies was investigated as a function of the sintering conditions, including the conventional one-step and the two-step sintering methods. The increase of sintering temperature leads to the relaxation of compressive stress, though no major effect on photoluminescence intensity was observed. The two-step sintering method revealed decoupling of densification and grain grown at sintering temperatures above about 1500°C. For sintering conditions of 1800/1700°C, dense ceramics with 97 + 0.2% of the theoretical density were obtained.

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