K. Kamada

Publications (27)29.22 Total impact

• Article: Deep trapping states in Cerium doped (Lu,Y,Gd)3(Ga,Al)5O12 single crystal scintillators

  E. Mihóková, K. Vávr\ru, K. Kamada, V. Babin, A. Yoshikawa, M. Nikl
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  ABSTRACT: We study deep trapping states in Ce3+-doped garnet crystals with the composition (Lu,Y,Gd)3(Ga,Al)5O12, recently shown as having remarkably high light yield. We use thermally stimulated luminescence (TSL) technique above room temperature and determine the composition Gd3Ga3Al2O12 as the host showing the lowest concentration of traps. This host consistently manifest very low afterglow comparable to that of the standard BGO crystal. We also perform TSL glow peak analysis based on the initial rise technique to evaluate trap depth and other characteristics associated with TSL peaks.
  11/2012;
• Article: Scintillator-oriented combinatorial search in Ce-doped (Y,Gd)3(Ga,Al)5O12 multicomponent garnet compounds

  K Kamada, T Yanagida, J Pejchal, M Nikl, T Endo, K Tsutumi, Y Fujimoto, A Fukabori, A Yoshikawa
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  ABSTRACT: Ce-doped (YyGd1−y)3(GaxAl1−x)5O12(x = 0, 1, 2, 3, 4 and y = 1, 2, 3) single crystals are grown by the micro-pulling down method. X-ray diffraction and electron probe microanalysis techniques are employed to check their structure and chemical composition, respectively. Optical and photoluminescence characteristics are measured and radioluminescence spectra, light yield and scintillation decay measurements are further made to evaluate the scintillation performance. We show that balanced Gd and Ga admixture in the Y3Al5O12 structure can considerably increase the scintillation efficiency, and the spectrally corrected light yield value exceeds 44 000 photon MeV−1. Scintillation decay times approach that of Ce3+ photoluminescence decay and an additional less intense slower component is also observed. Physical aspects of energy transfer process and 5d1 excited state depopulation are discussed. The micro-pulling down technique is shown as an ideal tool for a directed combinatorial search for targeted single crystal compositions to reveal those with the highest figure-of-merit for a given application field.
  Journal of Physics D Applied Physics 12/2011; 44(50):505104. · 2.54 Impact Factor
• Conference Proceeding: Read out test of inorganic-organic hybrid scintillator; Pr: LuAG single crystal covered with plastic scintillator

  K. Kamada, T. Yanagida, T. Endo, Y. Fujimoto, Y. Usuki, A. Yoshikawa
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  ABSTRACT: Read out test of inorganic-organic hybrid scintillator; Pr:LuAG single crystal covered with plastic scintillator are demonstrated. The Pr:LuAG sample coated with bis-MSB+TB-PVD containing WLS showed the better light output and energy resolution than the Pr:LuAG itself. Light output was increased up to 55% and energy resolution was also improved to 6.1%@662keV using APD (Hamamats S8664-8220). In the case of MPPC (Hamamatsu S10362_33_050 3600pixel-type), light output was increased up to 35% and energy resolution was also improved to 8.8%@662keV. Decay curve of the Pr:LuAG sample coupled with the WLS was also measured and successfully modeled.
  Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE; 12/2010
• Article: Development and Evaluations of Apatite Crystal Scintillators

  T. Yanagida, Y. Fujimoto, Y. Ohgi, Y. Yokota, A. Yoshikawa, H. Kagi, K. Sugiyama, K. Kamada
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  ABSTRACT: Five apatite crystal scintillators, which have chemical compositions of Ce 0.5%: Gd_9.33(SiO₄)₆O₂, Ce 0.5%: (Gd₈Sr₂)(SiO₄)₆O₂, Ce 5%:(Gd₈Sr₂) (SiO₄)₆O₂, Yb 0.5%:(Gd₈Sr₂) (SiO₄)₆ O₂ and Yb 3%:(Gd₈Sr₂) (SiO₄)₆ O₂ were grown by the micro-pulling down method. After cut and polishing processes, optical and radiation properties were evaluated. In a transmittance measurement, Ce doped crystals showed an absorption feature at approximately 300 nm and Yb doped ones 220 nm, respectively. When Ce-doped ones were excited by 340 nm photons, the emission peak appeared at approximately 400 and 440 nm, due to Ce³⁺ 5d-4f transitions. In Yb-doped series, 270 nm excitation caused emission peaking around 300 nm. The photoluminescence decay time kinetics of Ce-doped series were investigated. The Ce 0.5% doped (Gd₈Sr₂) (SiO₄)₆ O₂ showed about 23 ns decay constants, and the 5% doped one showed 14 ns. When coupled with Si-APD and irradiated by ²⁴¹Am α-ray, Ce doped scintillators showed 300-500 photons/5.5 MeV as α light yield.
  IEEE Transactions on Nuclear Science 07/2010; · 1.45 Impact Factor
• Article: Scintillation Properties of In Doped ZnO With Different In Concentrations

  T. Yanagida, Y. Fujimoto, A. Yoshikawa, Y. Yokota, M. Miyamoto, H. Sekiwa, J. Kobayashi, T. Tokutake, K. Kamada, S. Maeo
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  ABSTRACT: Using the liquid phase epitaxy (LPE) method we prepared the high crystalline quality In $^{3+}$ doped ZnO thin film scintillators with different Indium concentration of 26, 53, and 141 ppm. We evaluated their optical properties and radiation response, because there are few reports of radiation response of In-doped ZnO scintillator. In order to imitate the scintillator application, we measured the alpha-ray excited luminescence spectra. The emission bands peaking around 375 and 500 nm were observed, and with an increment of In $^{3+}$ , the intensity of both bands decreases. In the measurement of light yield, we optically coupled the sample with PMT R7600 by a silicone grease, and excitation was provided by $^{241}$ Am 5.5 MeV $alpha$ -rays. The samples showed of about 10% of the light yield of BGO scintillator which was used as a reference. Under the same excitation the scintillation decay was measured in all the samples as well.
  IEEE Transactions on Nuclear Science 07/2010; · 1.45 Impact Factor
• Article: Gamma-Ray Responses of Pr:LuYAP and Pr:YAP Scintillators

  T. Yanagida, K. Kamada, Y. Yokota, Y. Fujimoto, S. Maeo, A. Yoshikawa
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  ABSTRACT: Pr³⁺ doped LuYAP crystal was grown by the Czochralski method with 1 inch diameter and 10 cm length. In order to compare scintillation characteristics, Pr³⁺ doped YAP crystal was also grown by the micro-pulling-down method. Absorption spectra of them were measured and Pr³⁺ 4f → 4f5d and 4f2 → 4f absorption lines were observed at 230,470, and 600 nm, respectively. In photoluminescence measurements, here excited by Xe lamp pulse of wavelength around 223,250 and 280 nm emission lines due to Pr³⁺ 4f5d → 4f transition were detected. When coupled with PMT R7600 and irradiated by gamma-rays, gamma-ray induced light yields were estimated as 1900 ph/MeV for Pr: LuYAP and 5600 ph/MeV for Pr: YAP. In both crystals, light yield non-proportionality and energy resolution were investigated by individual lines in the gamma-ray energy range from 59.5 keV to 1408 keV. The gamma-ray excited decay time constants turned out to be 9.8 ns for Pr:LuYAP and 9.0 ns for Pr:YAP.
  IEEE Transactions on Nuclear Science 07/2010; · 1.45 Impact Factor
• Article: Development of Pr:LuAG Scintillator Array and Assembly for Positron Emission Mammography

  T. Yanagida, A. Yoshikawa, Y. Yokota, K. Kamada, Y. Usuki, S. Yamamoto, M. Miyake, M. Baba, K. Kumagai, K. Sasaki, M. Ito, N. Abe, Y. Fujimoto, S. Maeo, Y. Furuya, H. Tanaka, A. Fukabori, T. Rodrigues dos Santos, M. Takeda, N. Ohuchi
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  ABSTRACT: Abstract-In order to detect the breast cancer at the early stage with high efficiency, we intend to develop positron emission mammography (PEM), using Pr:LuAG single crystal as a scintillator of this scanner. PEM has the same mechanism of PET, where two 511 keV annihilation gamma-rays are detected by two gamma cameras at opposite side, and reconstruction of the data shows the position of the cancer with malignancy grades. After cutting and polishing processes for each crystal to a physical dimensions of 2.1 × 2.1 × 15 mm³, Pr:LuAG array covered with BaSO₄ reflector was used as a sensor head. The one camera unit consisted of 20 × 64 pixels optically coupled with three H8500-03 multi anode PMTs. Our PEM required four cameras at each side. Finally, eight cameras were installed in both sides of the prototype instrument and the spatial resolution was evaluated using the ¹⁸F in the breast phantom.
  IEEE Transactions on Nuclear Science 07/2010; · 1.45 Impact Factor
• Article: Single Crystal Growth, Optical Properties and Neutron Response of Doped

  A. Yoshikawa, T. Yanagida, Y. Yokota, N. Kawaguchi, S. Ishizu, K. Fukuda, T. Suyama, Kyoung Jin Kim, J. Pejchal, M. Nikl, K. Watanabe, M. Miyake, M. Baba, K. Kamada
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  ABSTRACT: Ce2%:⁶LiCaAlF₆ (⁶LiCAF) single crystal (nominal composition) with 2 mm in diameter and 50 mm in length was grown by the micro-pulling-down method. Emission from the perturbed Ce³⁺ centers was observed in an ¿-ray excited radioluminescence. The neutron response was compared with Li-glass (GS20, Saint-Gobain) using ²⁵²Cf. The scintillation decay time of Ce2%: ⁶LiCAF is 38 nsec, which is twice as short as that of GS20. Using Hamamatsu photomultiplier H7416 the photoelectron yield about a half of that of GS20 has been measured for the Ce: ⁶LiCAF single crystal . Considering the light yield of GS20 (6000 phot/neutron) and the spectral correction due to the different emission peak position in both materials, the light yield of Ce: ⁶LiCAF single crystal is estimated about 4200 phot/neutron.
  IEEE Transactions on Nuclear Science 01/2010; · 1.45 Impact Factor
• Conference Proceeding: Study of crystal growth and scintillation properties as a neutron detector of 2-inch diameter eu doped LiCaAlF6 single crystal

  N. Kawaguchi, T. Yanagida, Y. Yokota, K. Watanabe, K. Kamada, K. Fukuda, T. Suyama, A. Yoshikawa
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  ABSTRACT: Eu doped LiCaAlF₆ (Eu:LiCAF) single crystal with 2-inch in diameter was grown by Czochralski technique. The grown crystal was free from any visible inclusions or cracks. The neutron responses using ²⁵²Cf were compared with that of Li-glass (GS20, Saint-Gobain). The position dependence of light yield in Eu:LiCAF single crystal was measured and the average value was 9700 ± 900 photons/neutron.
  Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
• Article: Basic Properties of Ceramic Pr:LuAG Scintillators

  T. Yanagida, A. Yoshikawa, A. Ikesue, K. Kamada, Y. Yokota
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  ABSTRACT: This paper describes the first report of a Pr³⁺-doped transparent ceramic Lu₃Al₅O₁₂ (Pr:LuAG) scintillator. Transparent ceramic Pr0.25 mol% doped LuAG was developed by a sintering method, and achieved 70% transparency at wavelengths longer than 310 nm. The emission wavelength of the ceramic Pr:LuAG shifts to longer wavelengths than that of its single crystalline counterpart. The light yield was measured by irradiation of ¹³⁷Cs, and was almost half as that of the single crystalline counterpart. The energy resolution at 662 keV was 12% which was about three times as worse as that of the single crystalline one. The decay time showed a big difference with the single crystalline one because its slower component disappeared due to defects.
  IEEE Transactions on Nuclear Science 11/2009; · 1.45 Impact Factor
• Article: Scintillation Properties of Praseodymium Doped LuAG Scintillator Compared to Cerium Doped LuAG, LSO and

  L. Swiderski, M. Moszynski, A. Nassalski, A. Syntfeld-Kazuch, T. Szczesniak, K. Kamada, K. Tsutsumi, Y. Usuki, T. Yanagida, A. Yoshikawa, W. Chewpraditkul, M. Pomorski
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  ABSTRACT: Properties of praseodymium and cerium doped Lutetium Aluminum Garnet (LuAG) were compared with cerium doped Lutetium Oxyorthosilicate (LSO) and Lanthanum Bromide (LaBr₃). Light yield, its non-proportionality relative to 662 keV gamma -rays and the dependence of the energy resolution on energy of the detected gamma -rays were measured. LuAG:Pr turned out to have good proportionality, with deviation from unity around 10% at 16.6 keV and 3% at 59.5 keV. This, together with relatively high light yield of 5600 phe/MeV results in a very good energy resolution of LuAG:Pr of 5.1% measured with 662 keV gamma-rays. The measured time resolution of 308 ps is significantly larger than that of 166 ps obtained for LSO:Ce. This can be explained by smaller light yield of LuAG:Pr and the fact that only about 25% of its scintillation is emitted in short decay time modes of 17.6 ns and 52 ns, while the rest is decaying with long time modes of 1.4 mus and 9 mus.
  IEEE Transactions on Nuclear Science 09/2009; · 1.45 Impact Factor
• Article: Light Yield Non-Proportionality and Energy Resolution of Praseodymium Doped LuAG Scintillator

  L. Swiderski, M. Moszynski, A. Nassalski, A. Syntfeld-Kazuch, T. Szczesniak, K. Kamada, K. Tsutsumi, Y. Usuki, T. Yanagida, A. Yoshikawa
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  ABSTRACT: Scintillation properties of praseodymium doped LuAG have been investigated. The crystal is a dense (6.7 g/cm³) scintillator with a short decay time around 20 ns and wavelength emission spectrum peaked at 310 nm. The tested sample was 10 mm times 10 mm times 5 mm cuboid, polished on all surfaces. The dopant concentration amounts to 0.23 mo1%. A light yield of 16000plusmn1600 ph/MeV was measured using high sensitivity (13.7 muA/1mF) Photonis photomultiplier (PMT) XP5500B. High quantum efficiency of this PMT (35%) allowed us to register 5600plusmn400 phe/MeV using 12 mus shaping time in the spectroscopy amplifier. The measured energy resolution was equal to 5.0plusmn0.1%. Response of LuAG:Pr to gamma-rays was found to be proportional over wide energy range. Deviation from proportionality does not exceed 10% at 16.6 keV. This results in good intrinsic energy resolution of LuAG:Pr amounting to 3.0plusmn0.3%, measured with 662 keV gamma-rays from ¹³⁷Cs.
  IEEE Transactions on Nuclear Science 07/2009; · 1.45 Impact Factor
• Article: Scintillation Properties of 2-Inch-Diameter (LuAG) Single Crystal

  K. Kamada, T. Yanagida, K. Tsutsumi, Y. Usuki, M. Sato, H. Ogino, A. Novoselov, A. Yoshikawa, M. Kobayashi, S. Sugimoto, F. Saito
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  ABSTRACT: Pr:LuAG crystals possess interesting properties, such as high density, high light yield, and very fast 5d-4f emission decay time. Recently, we developed a Pr:LuAG single crystal with a diameter of 2 inches for scintillator applications, such as medical imaging. In this study, Pr-doped Lu₃Al₅O₁₂ (Pr:LuAG) single crystals with a diameter of 2 inches were grown by means of the Czochralski method; a body length of up to 90 mm was achieved. The Pr:LuAG crystals produced a homogeneous light yield with approximately 2.5 times less intensity compared to that produced by a conventional Ce:LSO crystal. A sample with dimensions of 5 mm times 5 mm times 1 mm exhibited energy resolutions of 4.8% at 662 keV, as measured by using a photomultiplier (PMT: Hamamatsu H6531), and 5.8% at 662 keV, as measured by using an Avalanche photodiode (APD: Hamamatsu S8664-55). The Pr:LuAG crystals exhibited a very fast rise time of approximately 0.4 ns, excited by a pulsed X-ray at room temperature. The decay time was approximately 18 ns, along with a noticeable presence of slower decay components (with a decay time of 55.0 ns). Furthermore, the Pr:LuAG crystals showed good linearity between the energy and pulse height within approximately 4% of the standard deviation in the range from 122 keV (¹⁵²Eu) to 1.4 MeV (²⁴¹Am) .
  IEEE Transactions on Nuclear Science 07/2009; · 1.45 Impact Factor
• Source

  Available from: Alan Owens

  Article: Scintillation Properties of Praseodymium Activated Single Crystals

  W. Drozdowski, P. Dorenbos, J.T.M. de Haas, R. Drozdowska, A. Owens, K. Kamada, K. Tsutsumi, Y. Usuki, T. Yanagida, A. Yoshikawa
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  ABSTRACT: Scintillation properties of LuAG:Pr grown by Furukawa Co. Ltd., Japan, have been studied. The best crystals display light outputs up to 19000 ph/MeV and an energy resolution of 4.6% at 662 keV. The scintillation yield is found to be a function of size and temperature of the sample; it can be enhanced by 40% upon heating to 450 K. Radioluminescence spectra show both d - f and f - f transitions of Pr³⁺ ions; the contribution of the latter increases with temperature. The scintillation decays are complex, with a fast decay constant of 20 ns. The presence of ¹⁷⁶Lu induces high background activity.
  IEEE Transactions on Nuclear Science 09/2008; · 1.45 Impact Factor
• Article: Energy Transfer to Pr Ions in Pr:Lu Al O (LuAG) Single Crystals

  A. Yoshikawa, K. Kamada, F. Saito, H. Ogino, M. Itoh, T. Katagiri, D. Iri, M. Fujita
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  ABSTRACT: Single crystals of LuAG doped with Pr³⁺ ions (0.2 mol%) are grown by the micro-pulling-down (mu-PD) method with an RF heating system. The as-grown crystals are confirmed to be of garnet-type structure with the space group of Ia3d (230). The emission-excitation spectra and luminescence decay kinetics are measured in the temperature range of 5-310 K by using synchrotron radiation as an exciting light source. The intrinsic luminescence is observed at 250 nm at low temperatures. Four emission bands at 308, 325, 360, and 380 nm are ascribed to the 5d-4f transitions of Pr³⁺ ions. From the decay kinetics measurements, it is pointed out that there exist two kinds of energy transfer mechanisms from the host LuAG lattice to the Pr³⁺ ions. The mechanisms of energy transfer are discussed in connection with the formation of substitution-type defects.
  IEEE Transactions on Nuclear Science 07/2008; · 1.45 Impact Factor
• Article: Single Crystal Growth and Luminescence Properties of CeF -CaF Solid Solution Grown by the Micro-Pulling-Down Method

  A. Yoshikawa, Kyoung Jin Kim, K. Aoki, K. Kamada, F. Saito, J. Pejchal, N. Solovieva, M. Nikl
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  ABSTRACT: (Ce_xCa_1-x)F_2+x single crystal with x = 0.0001 - 0.03 were grown by the mu-PD method. Ce³⁺ doping in CaF₂ lattice gives rise to characteristic absorption and emission bands, which are governed by the characteristics of the isolated Ce³⁺-F_i ^- C_4v pair centers and small clusters composed from these pairs. With increasing Ce concentration there is a strong increase of the absorption bands related to the cluster centres, but the radioluminescence spectra are always governed by the emission of the isolated Ce³⁺-F_i ^- C_4v pairs without noticeable changes in the emission band shape. Highest radioluminescence intensity is achieved for Ce 0.1{%} concentration and above 1{%} of Ce the onset of concentration quenching is observed. Scintillation response is governed by the energy transfer from the CaF₂ host lattice and even for the Ce3{%} sample the dominant scintillation decay time is about 50{%} longer with respect to the photoluminescence decay time of Ce³⁺-F_i ^- C_4v pair centres. Energy transfer processes and the role of different Ce³⁺-based centers are discussed.
  IEEE Transactions on Nuclear Science 07/2008; · 1.45 Impact Factor
• Article: Excitation Energy Transfer in CeF Single Crystals Doped With Sr

  A. Yoshikawa, K. Aoki, K. Kamada, F. Saito, M. Itoh, T. Katagiri, D. Iri, M. Fujita
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  ABSTRACT: CeF₃ single crystals heavily doped with Sr²⁺ ions are grown by the micro-pulling-down (mu-PD) method. The deviation of the composition in as-grown crystals is found to be entirely negligible. Three dimensional emission-excitation spectra are measured in a wide temperature range of 5-300 K by using synchrotron radiation as an exciting light source. Two intense emission bands are observed at around 320 and 400 nm. The origin of these bands is discussed on the basis of the perturbation effects introduced by Sr doping. It is pointed out that the energy transfer takes place from Ce³⁺ sites to defect sites when the crystal is warmed from 5 to 300 K.
  IEEE Transactions on Nuclear Science 07/2008; · 1.45 Impact Factor
• Article: Crystal Growth and Scintillation Properties of 2-Inch-Diameter (Pr:LuAG) Single Crystal

  K. Kamada, K. Tsutsumi, Y. Usuki, H. Ogino, T. Yanagida, A. Yoshikawa
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  ABSTRACT: In this work we tried to grow 2-inch-diameter and high quality Pr:LuAG single crystals by the Czochralski (Cz) method. To grow the large diameter Pr:LuAG single crystal, we have optimized growth conditions and the furnace design. As a result, we have succeeded in the growth of 2-inch-diameter Pr:LuAG single crystal with a length of 110 mm. To determine light yield and energy resolution the energy spectra were collected under 662 keV gamma-ray excitation (¹³⁷Cs source) and detection by a photomultiplier (Hamamatsu H7826). The light yield was around three times higher than that of BGO and almost homogeneous with increasing solidification fraction up to 0.32. The energy resolution was around 8%. Furthermore, scintillation decay time was around 23 ns and almost homogeneous all over the crystal.
  IEEE Transactions on Nuclear Science 07/2008; · 1.45 Impact Factor
• Article: Suppression of Host Luminescence in the Pr:LuAG Scintillator

  H. Ogino, K. Kamada, A. Yoshikawa, F. Saito, J. Pejchal, J.A. Mares, M. Nikl, A. Vedda, J. Shimoyama, K. Kishio
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  ABSTRACT: Effect of Ga substitution in the (Lu,Pr)₃Al₅O₁₂ (Pr :LuAG) scintillator was examined at the crystals grown by the micropulling down (mu-PD) method. Host luminescence due to an exciton localized around the Lu-Al antisite defect was suppressed by Ga admixture. Concentration dependence was investigated and suppression was observed even at the lowest Ga concentration of 5 mol%. Faster decay time as well as less intense slower components were obtained upon increasing the amount of Ga. In the thermostimulated luminescence measurement, the glow curve peaks are gradually shifted to lower temperatures with the gallium admixture, and noticeable intensity decrease was observed only for the (Lu,Pr)₃(Ga_0.2Al_0.8)₅O₁₂. The undesired quenching effect of Ga on the Pr³⁺ luminescence seems to be reasonably low up to (Lu,Pr)₃(Ga_0.2Al_0.8)₅O₁₂ sample. It is estimated to introduce nonradiative losses of less than 10% with respect to Ga-free Pr:LuAG. Bulk crystals were also grown by the Czochralski (Cz) method and these effects were confirmed.
  IEEE Transactions on Nuclear Science 07/2008; · 1.45 Impact Factor
• Article: Luminescence characteristics and energy transfer in the mixed YxGd1−xF3:Ce, Me (Me = Mg, Ca, Sr, Ba) crystals

  M Nikl, K Kamada, A Yoshikawa, A Krasnikov, A Beitlerova, N Solovieva, J Hybler, T Fukuda
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  ABSTRACT: The luminescence spectra and decay kinetics are measured within 80–300 K for the set of mixed YF3–GdF3 single-crystal fluoride hosts doped by the Ce3+ and Me2+ (Me = Mg, Ca, Sr, Ba) ions. For certain Ce and Me concentration ranges we observe creation of the Ce3+-distorted luminescence centre with the emission maximum around 380–390 nm. Energy migration through the Gd sublattice and a transfer to the Ce3+-distorted centre is evidenced and modelled using a simple Stern–Volmer approximation.
  Journal of Physics Condensed Matter 02/2006; 18(11):3069. · 2.55 Impact Factor