Structural,morphological and photoluminescence characterizations of Sm^(3+) doped Y_(2)O_(3) nano-sized phosphors synthesized by ultrasound assisted sol-gel method

Nanosized 1 at% Sm^(3+)doped Y_(2)O_(3)powders were prepared by an ultrasound assisted sol-gel method.Y_(2)O_(3):Sm^(3+)powders crystallize in Y_(2)O_(3)pure cubic phase and XRD analysis shows that the as-used agitation protocol affects strongly the crystallite’s shape and mean size.The recorded emission spectra under λ_(em)=600 nm exhibit two absorption bands;the first one is assigned to O^(2-)→Sm^(3+)charge transfer state(CTS) with a maximum absorption at 223 nm,and the second is due to intraconfigurational transition 4f^(5)-4f^(5) of Sm^(3+) with a maximum absorption at 407 nm.The 223 and 407 nm transitions are attributed to characteristics intra-configurational transitions of Sm^(3+).All emission spectra are dominated by reddish/orange luminescence located at 606 nm and assigned to ^(4)G_(5/2)→^(6)H_(7/2) transition.It is found that the photoluminescence intensity of samples obtained under excitation at 407 nm is 60 times smaller than that obtained under 223 nm excitation.Decay time measurements of the ^(4)G_(5/2)→^(6)H_(7/2) luminescence transition indicate that decay time of nano-sized powder is significantly shorter than bulk material one.

Effect of annealing atmospheres on the scintillation properties of Ce^(3+)‑doped YAG nanoscintillator

Background In this study,three sample detectors have been prepared by using cerium-activated YAG nanoscintillator(Y_(3)Al_(5)O_(12):Ce^(3+))synthesized by sol-gel method and heat-treat at 900°C for 2 h in different atmospheres such as vacuum,air and nitrogen.Purpose Many studies about YAG:Ce^(3+)single crystal have been carried out,but the material at the nanoscale remains not enough understood.The objective of the present paper is to investigate the effects of annealing atmosphere on the scintillation properties and identify the suitable atmosphere that allow to design radiation detectors with high scintillation efficiency.Methods In order to accurately assess the scintillation properties,the nanoscintillator sample powders have been designed as a detector,in which,preparation operations such as surface homogenization and efficiency coupling with photomultiplier tube(PMT)window were developed.The study was performed usingγ-rays 662 keV released from137Cs radioactive source,the bi-alkali GDB-4FF PMT was used as a photodetector.Nuclear instrumentation chain was set up in order to collect the pulse height spectra,NaI:Tl single-crystal scintillator was used as a reference detector to estimate the scintillation light yield.The delayed coincidence method was used for measuring the scintillation decay time of nanoscintillator sample detectors.Results The sample detector annealed at vacuum atmosphere exhibits the best scintillation properties,the scintillation light yield was estimated to be 14,600±3400 ph/MeV and the fast component in the scintillation decay was 90 ns.Conclusion The vacuum is the suitable atmosphere which allows the development of radiation detectors with high scintillation efficiency.