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For many years, rare-earth (RE)-doped glasses have been a subject of extensive research owing to their potential uses in laser and optoelectronics industries. For instances of, the radiation dosimeter, fiber laser and optical amplifier fields,
Ag+, Er3+, Nd3+, Pr3+, and Yb3+ -doped glasses have been developed and used. Glasses can easily be fabricated in desired shapes and sizes as well as are cost and time effective to synthesize, as compared to other RE-doped optically active transparent materials. The development of such potential and technologically important holding glasses is underway to minimize limitations and broaden the application fields. Low external and internal quantum efficiencies and high non-radiative transition probabilities are the main limiting issues of the glasses. These limiting issues could be resolved by modifying the glass matrix as well as by embedding nano-sized crystals. Therefore, the objective of this study was to prepare Eu3+ -doped glasses for a scintillator and red light-emitting solid-state device applications as well as to optimize the technique to fabricate the nano-sized CsPbBr3-embedded glasses for their application in scintillator and green light-emitting devices.
The Eu3+ -doped borosilicate glasses of 0≤Eu2O3≤2.5 mol% and phosphate glasses of 0≤Eu2O3≤5 mol% were fabricated by the conventional melt-quenching technique. The glasses were analyzed for various physical and optical properties at the room and low temperatures (down to 10K). Optimum photoluminescence emissions were recorded in 2.5 and 3 mol% doped borosilicate and phosphate glasses, respectively. Both of the glass systems exhibited strong X-ray induced emission without any concentration quenching. Photoluminescence increased with decreasing temperature. The Judd-Ofelt intensity parameters and spectroscopic properties were measured using a customized program. The calculated photoluminescence quantum efficiency for the 5D0→7F2 transition was only 29% and 45% for the borosilicate and phosphate glasses, respectively. The results of intense X-ray luminescence, increasing photoluminescence on decreasing temperature and moderate photoluminescence quantum efficiencies indicate that the glasses might extend their scope in the application field of X-ray detection, temperature sensor, and red light-emitting optical device technologies.
Furthermore, an in situ crystallization technique of the CsPBr3 nano-sized crystal inside the phosphate glass was developed. Three different glasses with varying concentrations of the Cs2CO3, PbBr2, and NaBr3 were prepared by melting at 1573K. The glass with the highest concentration (PG10) was analyzed through the transmission electron microscopy. The crystalline size of the glass was 6-10 nm. The glass showed green emission at 340-350 nm excitation and had 23-32 nm full width at half maximum. The glass prepared at 1473K with the highest concentration (PG10) showed weak X-ray luminescence. The successful crystallization of CsPbBr3 inside the glass matrix may establish wider applications of the CsPbBr3 in an ambient environment without any property degradation.
Thesis Advisor: Prof. Hongjoo Kim