Photoluminescence characterization and morphology control of inorganic phosphor particles

無機蛍光体粒子のフォトルミネッセンス特性評価及び形態制御

Minami Takaaki

The objective of this thesis is to investigate the photoluminescence characterization and morphologic control of inorganic phosphor particles. Both solid/dense and porous particles of europium-doped yttrium oxide (Y_2O_3:Eu^<3+>), and newly synthesized carbon-based boron oxynitride (BCNO) phosphors were selected as model materials. The major conclusions of this thesis can be summarized as follows.

Chapter 1 discusses the background, previous research, methods used to investigate photoluminescence phenomena, current state of the field, and problems associated with inorganic phosphors.

Chapter 2 describes the relationship between photoluminescence and both the particle and crystallite size of Y2O3:Eu^<3+> fine particles. The crystallite and particle sizes played different roles in the control of the photoluminescence characteristics of the phosphors. The blue-shift of the charge transfer band in the excitation spectra was mostly due to the particle-size effect. In contrast, the decrease in the crystal symmetry ratio, which is the ratio of the C_2 to C_<3i> sub-lattice populations in the photoluminescence emission spectra, was primarily due to the effect of crystallite size.

Chapter 3 demonstrates the effect of porosity on the photoluminescence of Y2O3:Eu^<3+> fine particles. The porous particles exhibited greater red-emission rendering properties than that of non-porous particles, based on the CIE chromaticity diagram. The photoluminescence intensity and quantum efficiency exhibited by the porous particles are greater than that of non-porous particles because the porous particles are hollow. Porous particles have unique photophysical properties, such as a 4-nm blue-shift in the charge-transfer and a lower symmetry ratio of 2.7, which were not exhibited byIIthe non-porous particles with a particle size of 757 nm and a crystallite size of approximately 30 nm. The properties of sub-micrometer porous particles were identical to those of non-porous particles, which have reduced particle and crystallite size compared with porous particles.

Chapter 4 presents a detailed chemical analysis and photoluminescence characterization of the BCNO phosphors. The resulting powder has high external quantum efficiency with a direct band-gap transition. The BCNO phosphors have these properties because the atomic distances of the BCNO are less than those of conventional BCN compounds, which have an indirect band-gap transition and low quantum efficiency. The smaller atomic distances of the BCNO result from the presence of oxygen atoms, which have higher electron affinity and smaller covalent-bond radii compared with boron, carbon and nitrogen.

A simple summary and comments regarding future investigations are provided in Chapter 5.

Chemical technology [ 570 ]

eng

Copyright(c) by Author

Chapter 1, T. Minami and S. Hirayama : High quality fluorescence decay curves and lifetime imaging using an elliptical scan streak camera, J. Photochem. Photobio A: Chemistry, 53 (1990), pp. 11-21 references

Chapter 2, T.Minami, W-N Wang, F. Iskandar, and K. Okuyama : Photoluminescence properties of submicrometer phosphors with different crystallite/particle sizes, Jpn. J. Appl. Phys, 47 (2008), pp. 7220-7223 references

Chapter 3, Widiyastuti, W., T. Minami, W-N. Wang, F. Iskandar, and K. Okuyama : Photoluminescence Characteristics of Macroporous Eu-Doped Yttrium Oxide Particles Prepared by Spray Pyrolysis, Jpn. J. Appl. PhysJpn. J. Appl. Phys. 48 (2009) 032001 references

Chapter 4, T.Minami, W-N. Wang, Y. Kaihatsu, F. Iskandar, and K. Okuyama : Photoluminescence and Electron Energy Loss Specta Analysis of New Carbon-based Boron Oxynitride Phosphor Particles, J. Mater. Sci. in review references

[DOI] http://dx.doi.org/10.1016/1010-6030(90)87108-N references

[DOI] http://dx.doi.org/10.1143/JJAP.47.7220 references

[DOI] http://dx.doi.org/10.1143/JJAP.48.032001 references

広島大学