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Concentration Quenching of Tb3+ Luminescence in TbxYb3-XAl5O12 Single Crystals
M.Nikl,N.Solovieva,A.Yoshikawa,YujiKagamitani,T.Fukuda 한양대학교 세라믹연구소 2003 Journal of Ceramic Processing Research Vol.4 No.3
Tb-doped Yb3Al5O12 and Y3Al5O12 single crystals were grown by the micropulling-down method in the form of rods of 2 mm diameter and a few cm in length. Emission spectra and decay times of Tb3+ luminescent centers were measured for Tb concentrations in a Y(Yb) sublattice of (1-70) %. A noticeable decrease of the emission intensity and decay time was obtained for Tb concentrations above 15% and 30% for Y3Al5O12 and Yb3Al5O12 hosts, respectively. Both effects are ascribed to the concentration quenching of Tb3+ luminescence due to energy migration over the Tb3+ subsystem and subsequent energy transfer to unspecified nonradiative traps. Energy migration process and structural aspects are discussed.
Kamada, K.,Nikl, M.,Kurosawa, S.,Shoji, Y.,Pejchal, J.,Ohashi, Y.,Yokota, Y.,Yoshikawa, A. Elsevier [etc.] 2016 Journal of luminescence Vol.169 No.2
Pr doped (Lu,Gd)<SUB>3</SUB>(Ga,Al)<SUB>5</SUB>O<SUB>12</SUB> single crystals were grown by the micro-pulling down (μ-PD) method. The crystals were greenish and transparent with 3.0mm in diameter, 10-30mm in length. Neither visible inclusions nor cracks were observed. Luminescence and scintillation properties were measured. The substitution at the Al<SUP>3+</SUP> sites by Ga<SUP>3+</SUP> in garnet structure has been studied. The Pr<SUP>3+</SUP> 5d-4f emission is observed within 300-380nm wavelength superposed with 312nm emission line of Gd<SUP>3+</SUP>. Pr0.2%:Lu<SUB>2.5</SUB>Gd<SUB>1</SUB>Ga<SUB>3</SUB>Al<SUB>2</SUB>O<SUB>12</SUB> shows highest emission intensity. The light yield of Pr0.2%:Lu<SUB>2.5</SUB>Gd<SUB>0.5</SUB>Ga<SUB>2</SUB>Al<SUB>3</SUB>O<SUB>12</SUB> sample with diameter 3mmx1mm size was around 8000ph/MeV. Two-exponential approximations of scintillation decay showed 39.6ns (30.6%) and 151ns (69.4%) decay times.
Health Monitoring for Large Structures using Brillouin Distributed Sensing
Thevenaz, L.,Chang, KT.,Nikles, M. The Korean Society for Nondestructive Testing 2005 한국비파괴검사학회지 Vol.25 No.6
Brillouin time-domain analysis in optical fibres is a novel technique making possible a distributed measurement of temperature and strain over long distance and will deeply modify our view about monitoring large structures, such as dams, bridges, tunnels and pipelines, Optical fibre sensing will certainly be a decisive tool for securing dangerous installations and detecting environmental and industrial threats.
Chewpraditkul, W.,Bruza, P.,Panek, D.,Pattanaboonmee, N.,Wantong, K.,Chewpraditkul, W.,Babin, V.,Bartosiewicz, K.,Kamada, K.,Yoshikawa, A.,Nikl, M. Elsevier [etc.] 2016 Journal of luminescence Vol.169 No.1
The optical and scintillation properties of Ce<SUP>3+</SUP>-doped YGd<SUB>2</SUB>Al<SUB>5-x</SUB>Ga<SUB>x</SUB>O<SUB>12</SUB> (x=2,3,4) single crystals were investigated. With increasing Ga content in the garnet host, the 5d<SUB>1</SUB> absorption and emission bands shift toward higher energy due to the decrease in the crystal field splitting of the 5d levels. Temperature dependences of absorption and emission spectra and of photoluminescence decays of both prompt and delayed components were measured. Light yield (LY) and its dependence on an amplifier shaping time were measured under excitation with γ-rays. High LY value of 38,000photons/MeV was obtained for a YGd<SUB>2</SUB>Al<SUB>2</SUB>Ga<SUB>3</SUB>O<SUB>12</SUB>:Ce sample. Scintillation decay was measured with an extended dynamical and temporal scale under the nanosecond-pulsed soft X-ray excitation. The relative content of the fastest component in the scintillation response increases with increasing Ga content.