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

南 孝明

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.

化学工業 [ 570 ]

英語

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 ～を参照している

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 ～を参照している

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 ～を参照している

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 ～を参照している

[DOI] http://dx.doi.org/10.1016/1010-6030(90)87108-N ～を参照している

[DOI] http://dx.doi.org/10.1143/JJAP.47.7220 ～を参照している

[DOI] http://dx.doi.org/10.1143/JJAP.48.032001 ～を参照している

広島大学