Optical and scintillation properties of Tb-doped apatite single crystals

Takayuki Yanagida,Noriaki Kawaguchi 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.6

In the present study, we focus on the Tb-doped Sr-based apatite materials which have a chemical composition of Sr2RE8(SiO4)6O2 where RE denotes the rare earth element. The target materials in this study were Tb 0.5% doped Sr2Gd8(SiO4)6O2, Sr2Y8(SiO4)6O2, Sr2(Gd0.5Lu0.5)8(SiO4)6O2 and Sr2(Gd0.4Lu0.6)8(SiO4)6O2 crystals, and they were synthesized by the floating zone method. When we checked powder X-ray diffraction patter, we confirmed a single phase (JCPDS No:280212) for all the samples. In photoluminescence (PL) and X-ray induced scintillation spectra, some sharp emission lines appeared, and the emission origin was Tb3+ 4f-4f transition. We investigated PL and scintillation decay time profiles, and the main component was 1.8 and 1.3 ms, respectively. Among the samples prepared here, Sr2Gd8(SiO4)6O2 showed the highest scintillation intensity.

Scintillation properties of Pr-doped Li2O-GeO2 glasses

Noriaki Kawaguchi,Takayuki Yanagida 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.5

We have investigated scintillation properties of the Pr-doped Li2O-GeO2 glasses. From the transmittance spectra, absorption bands due to 4f-4f transition of Pr3+ ions were observed. The samples showed the X-ray induced radioluminescence peaks originating from the 4f-4f transitions of the Pr3+ ion. The scintillation decay times were from 2.07 to 3.12 µs which are acceptable values for the scintillator. The Pr-doped Li2O-GeO2 glasses can be regarded as the candidate for the scintillation materials.

Dosimetric properties of Mg-doped Al2O3 transparent ceramics

Takumi Kato,Noriaki Kawaguchi,Takayuki Yanagida 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.5

Transparent ceramics of Al2O3 doped with different concentrations of Mg2+ ions (0.001, 0.01, 0.1 and 1.0%) were synthesized by the Spark Plasma Sintering (SPS) method, and scintillation and dosimetric properties were investigated. Under X-ray irradiation, all the samples showed emission peaks around 310, 380 and 693 nm. Based on the measured scintillation decay times and previous studies, the origins of the emission peaks at 310, 380 and 693 nm were attributed to F+ centers, F centers and Cr3+ impurity ions, respectively. The 0.1% Mg-doped sample showed a glow curve consisting of peaks around 50, 105, 135, 230, 350 and 400 oC. All the samples had a linear TSL response in a dose range from 0.1 to 1,000 mGy.

Scintillation and photoluminescence properties of Prdoped CaHfO3 crystals

Hiroyuki Fukushima,Daisuke Nakauchi,Noriaki Kawaguchi,Takayuki Yanagida 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.3

Pr-doped CaHfO3 bulk crystals were synthesized by the floating zone method, and the luminescence properties wereinvestigated. We confirmed that all the samples have a single phase of CaHO3 by XRD measurement. The undoped sampleindicate a broad emission around 440 nm and fast decay time constant due to the host while the Pr-doped samples show sharppeaks and slow decay time constants due to the 4f-4f transitions of Pr3+. By Pr-doping, the afterglow level became worse thanthat of the undoped one while the dense Pr-doping can suppress the afterglow.

Photo- and radio- luminescence characterizations in rare-earth-doped SrAl2O4 crystals

Daisuke Nakauchi,Masanori Koshimizu,Noriaki Kawaguchi,Takayuki Yanagida 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.4

SrAl2O4 bulk crystals doped with all rare-earth (RE) ions except for Sc, Y, La, Pm and Lu were synthesized by the optical floating zone method to systematically investigate the photoluminescence (PL) and radioluminescence (RL) properties for radiation detector applications. The crystal samples show PL and RL signals due to the 5d-4f or 4f-4f transitions of doped RE ions, and each decay curve consists of a sum of exponential functions with the typical decay time constants. Under VUV photon excitation, the Ce-, Pr-, Eu-, Tb-, Dy- and Ho-doped samples exhibit PL predominantly with two broad emission bands around 320 and 600 nm, which are possibly due to self-trapped excitons (STEs) perturbed by RE ions.

Radio-photoluminescence properties of CaF2 transparent and opaque ceramics

Kato Takumi,Nakauchi Daisuke,Kawaguchi Noriaki,Yanagida Takayuki 한국물리학회 2020 Current Applied Physics Vol.20 No.11

Radio-photoluminescence (RPL) phenomenon was observed in CaF2 transparent and opaque ceramics by X-ray irradiation. The RPL appeared as a formation of photoluminescence (PL) emission bands located around 660 and 720 nm caused by F2+ and (F2+)A centers, respectively. The RPL signal can be deleted by heating, and reusability was observed over ten experimental cycles. The fading of the RPL signal was confirmed to be ~4% in 10 days. The detectable RPL response of CaF2 transparent ceramics was as low as 1 mGy, and the dynamic ranges were confirmed over 1–10000 mGy with linear response.

Radio-photoluminescence observed in non-doped Mg2SiO4 single crystal

Go Okada,Takahiro Kojima,Jisaburo Ushizawa,Noriaki Kawaguchi,Takayuki Yanagida 한국물리학회 2017 Current Applied Physics Vol.17 No.3

The aim of this research is to investigate radiation-induced luminescence of non-doped Mg2SiO4 single crystal. The Mg2SiO4 single crystals were synthesized by the Czochralski process. The obtained crystal samples were studied to characterize the radio-photoluminescence (RPL), radio-luminescence (RL), and thermally-stimulated luminescence (TSL) properties. A non-irradiated (or as-prepared) sample shows no particular PL features whereas X-ray treated sample shows a broad PL emission around 630 nm under excitation at 270 nm. The latter observation indicates that RPL centre has been generated by X-ray irradiation. The X-ray induced RL can be observed due to the RPL centre around 630 nm, and the intensity monotonically increases with accumulating the incident radiation dose. TSL glow curve consists of three peaks at 160, 260, and 390 C, and the initial rise method derived the activation energies of 1.33, 1.47, and 1.85 eV, respectively. The first two TSL are associated with some shallow trapping centres, and annealing at this temperature range builds up the RPL response. On the other hand, annealing at higher temperatures supresses the RPL response; thus, the RPL centre is located at deeper site.

X-ray induced effects in Sm3+-doped ZnO-P2O5 glass for radiation measurements

Go Okada,Hirokazu Masai,Aya Torimoto,Safa Kasap,Takayuki Yanagida 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.3

We have studied X-ray induced effects on ZnO-P2O5 glass doped with Sm3+ ion. The glass was synthesized by a conventionalmelt-quenching method in an ambient atmosphere. We have investigated the following three different effects induced by Xrayirradiation in this glass, which can be used for radiation sensing applications. First, although the as-prepared glass sampleis highly transparent and homogeneous, upon irradiation with X-rays, the sample becomes slightly brownish due to anappearance of color centers induced by X-ray irradiation which can be measured as an optical absorption in the UV-Vis range. By utilizing the extent of absorption change by X-ray irradiation, it is possible to measure the incident radiation dose fromabout 0.5 to over 20 Gy. Second, with the Sm3+ ion included as a luminescent centre, the glass sample emits orange-red lightupon X-ray irradiation. The integrated light emission is proportional to the incident X-ray dose, hence it can be used as ascintillator plate for online radiation monitoring. The confirmed exposure dose detection range for this use is approximately1 -300 R. Last, when an irradiated sample is heated at elevated temperatures from 100 to 400 oC, it shows a thermallystimulatedluminescence (TSL). The emission intensity increases with the accumulated X-ray dose delivered prior to themeasurement, so our sample has a function to act as a TSL dosimeter as well. Over the radiation dose range we have tested,the X-ray induced effects above show linear response against the incident dose. The linear response is of particular importancefor dosimetry applications since it enables us to calibrate the response of sample to radiation dose with high accuracy.