Nakarin Pattanaboonmee

Luminescence properties and scintillation response in Ce3+-doped Y2Gd1Al5-xGaxO12 (x = 2, 3, 4) single crystals

The compositional dependence of luminescence properties and scintillation response were investigated in Ce3+-doped Y2Gd1Al5-xGaxO12 (x = 2, 3, 4) single crystals. The Gd3+ → Ce3+ energy transfer was evidenced by photoluminescence excitation spectra of Ce3+ emission. With increasing Ga content in the garnet host, the Ce3+ luminescence from the lowest 5d level (5d1) is shifted toward higher energy due to the decrease in the crystal field splitting of the 5d levels. Light yield (LY) and its dependence on the amplifier shaping time were measured under excitation with γ-rays. High LY value of ∼38 000 ph/MeV was obtained for a Y2Gd1Al3Ga2O12:Ce sample. Scintillation decay was measured with an extended dynamical and temporal scale under the nanosecond pulse soft X-ray excitation. The decrease of both LY value and relative contribution of slower decay component in the scintillation response was observed with increasing Ga content in the garnet host.

Physical, Structural and Luminescence Properties of ZnO-Bi2O3-B2O3 Glass System

The ZnO-Bi2O3-B2O3 (ZBB) glasses with different concentrations of Bi2O3 have been prepared by a conventional melt quenching technique and investigated the effect of Bi2O3 on the physical, structural and luminescence properties. The density and hardness of glasses are also measured and found to increase with increase of Bi2O3 concentration. The IR studies indicate that these glasses are made up of [BiO3], [BO3], [BO4] and [B basic structural units. From optical spectra, the cut-off wavelengths were shifted from 423 nm to 447 nm as the content of Bi2O3 increases from 15 to 30 mol%. The photoluminescence spectra exhibit characteristic peaks at 602 nm corresponding to 3P11S0 transitions of Bi3+. The decay time for 3P1 level of Bi3+ increases with increase of Bi2O3 concentration.

Luminescence and Light Yield in Ce3+-Doped Y1Gd2Al5-xGaxO12 (x=2,3,4) Single Crystal Scintillators

The compositional dependences of luminescence properties and light yield were studied in Ce3+ -doped Y1Gd2Al5-xGaxO12 (x = 2, 3, 4) single crystal scintillators. The Gd3+→ Ce3+ energy transfer was evidenced by photoluminescence excitation spectra of Ce3+ emission. With increasing Ga content in the garnet host, the Ce3+ luminescence from the lowest 5d level (5d1) was blue-shifted due to the decrease in the crystal field splitting of the 5d levels. High light yield (LY) value of ~36,000 ph/MeV was obtained for a Y1Gd2Al2Ga3O12:Ce sample under excitation with 662 keV γ-rays. The decrease of LY value was also observed with higher Ga content due to the thermal ionization from the 5d1 level to the conduction band.

Growth and Characterization of L-Arginine Doped Potassium Dihydrogen Phosphate Single Crystals Grown by Sankaranarayanan-Ramasamy Method

Single crystals of L-arginine doped potassium dihydrogen phosphate (KDP) were grown by both conventional and Sankaranarayanan-Ramasamy (SR) methods. The grown crystals were characterized by powder X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, optical transmission, dielectric constant, and Vickers microhardness. The reflectance and extinction coefficients of the grown crystal were calculated and discussed. The variations of dielectric constant, dielectric loss, a.c. resistivity and a.c. conductivity were studied. The lower values of dielectric loss due to fewer defects were observed in SR grown L-arginine doped KDP crystals. Vickers microhardness study showed higher mechanical stability in SR method grown crystals.

Luminescence and Scintillation Response of Ce3+-Doped Oxide Glasses with High Gd2O3 Content

This report presents the luminescence and scintillation response of Ce3+-doped oxide glasses with high Gd2O3 (30 mol%) content. The characteristic emission of Ce3+ 5d → 4f transition peaking around 380 nm was observed in its luminescence spectra under UV and X-ray excitation. Photoluminescence decay kinetics was governed by a few tens of nanoseconds decay time. The integral scintillation efficiency of about 22% of that of the Bi4Ge3O12 scintillator was obtained under X-ray irradiation. The light yield and its dependence on the integration time were measured and compared with that of the Bi4Ge3O12 crystal. The total mass attenuation coefficient at 662 keV γ-rays was also determined and compared with the theoretical one calculated using the WinXCom program.

Effects of Ga Content on Optical and Scintillation Properties in Ce3+-Doped YGd2(Al,Ga)5O12 Scintillators

The optical and scintillation properties of Ce3+-doped YGd2(Al,Ga)5O12 single crystal scintillators were investigated. The Ce3+ 5d-4f emission was blue-shifted with increasing Ga content due to the decrease of the crystal field strength. Temperature dependence of the photoluminescence decay times was measured and the thermal activation energy for the luminescence quenching was calculated. Light yield (LY) and its dependence on an integration time were measured under γ-ray excitation. The fast component content in the scintillation response increases with increasing Ga content. The YGd2Al2Ga3O12:Ce sample showed a high LY of 38,000 photons/MeV. The decrease of LY value observed for a YGd2Al1Ga4O12:Ce sample is mainly due to the thermal ionization of the 5d1 excited state of the Ce3+ emission center to the conduction band.

Growth and Characterization of Ammonium Dihydrogen Phosphate (ADP) Doped with H3BO3 Crystals Grown by Slow Evaporation Method

Ammonium dihydrogen phosphate (ADP) crystals is very interesting due to its nonlinear optical property. This study investigated on improving of material for academic use by adding boric acid to modify ADP crystals. Slow evaporation method in aqueous solutions of pure ADP and ADP doped with three concentrations of H3BO3 as 0.1, 1.0, 5.0 %wt were studied. The grown crystals were confirmed tetragonal structure by powder X-ray diffraction studies. The FTIR spectrum analysis presented various functional groups of boron in three conditions of doped ADP. TGA study was comfirned the temperature stability at 220 °C for both pure and doped ADP crytals. The machanical stress was analyzed by Vicker’s hardness measurement. The results of this analysis showed boric acid doped 1.0 %wt had superior machanical stress from 10 to 75 grams. ADP doped with boric acid at 1.0 %wt was accepted in all test properties.

Photo- and Radioluminescence of Ce3+-Doped Dense Oxide Glass

Photo-and radioluminescence characteristics of Ce3+-doped dense oxide glass (SiO2-B2O3-Al2O3-Gd2O3) are presented. The Gd3+→ Ce3+ energy transfer was evidenced by photoluminescence excitation spectra of Ce3+ emission. Photoluminescence decay kinetics was governed by a few tens of nanoseconds decay time. The integral scintillation efficiency of about 22% of that of the Bi4Ge3O12 scintillator was obtained under X-ray irradiation. Scintillation light yield under alpha particle excitation was measured and compared with that of the Bi4Ge3O12 crystal.

Low-Temperature Synthesis of Nanocrystalline ZnO Nanorods Arrays

In this present research, vertically aligned ZnO nanorods arrays were grown on silicon wafer (100) substrates from a zinc nitrate hexahydrate and hexamethylenetetramine solution by a cost effective and low temperature (90 °C) hydrothermal growth method. Field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) were used to analyze morphology, crystallinity and film thickness, respectively. It was demonstrated that when the seed layer thickness change from 18 to 200 nm, the nanowire density increased. Our result presented a scalable method for fabricating ZnO nanorods arrays with potential for a lots of application such as micro/nanosensors and the nanoelectronic devices.

Growth and Characterization of Boric Acid Doped KDP Single Crystals Grow by Slow Evaporation Method

Boric acid (0.25, 0.5, 1.0 %wt) doped Potassium Dihydrogen Phosphate (KDP) bulk single crystals were grown from aqueous solutions by slow evaporation method. Solubility and nucleation curves were studied. The grown crystals were confirmed by powder X-ray diffraction analysis. Functional groups presented in the grown material have been identified using FTIR spectra. The temperature stability of the crystal has been confirmed by TGA. The mechanical strength was analyzed using Vickers hardness measurement.