Zhaoyang Chen

Synthesis and luminescence in LiMgPO4:Tb,Sm,B phosphors with possible applications in real-time dosimetry

The objective of this work was to develop possible materials for optically stimulated luminescence (OSL) dosimetric applications in real-time measurement. A novel material of LiMgPO4:Tb,Sm, B was prepared by solid-state diffusion method at 900 degrees C. The structure and optical properties of these phosphors were characterized by X-ray diffraction, fluorescence spectrophotometer, and OSL reader. The results showed that the full discrimination between the stimulation and emission spectra made them very fit for the optic-fibre dosimetry. The OSL vs. dose response was linear in the dose range of 0.1 to 216 Gy. It also showed a significant improvement in the stimulation time compared with LiMgPO4:Tb,B. Hence, the phosphor could be used in the real-time dosimeter based on the OSL technology for medical monitoring as well as for environmental dosimetry and space dosimetry.

Preparation and thermal-sensitive characteristic of copper doped n-type silicon material

Copper doped n-type single-crystal silicon materials are prepared by a high temperature diffusion process. The electrical and thermal-sensitive characteristic of materials is investigated under different experimental conditions. The results show that the maximum resistivity of 46.2 Ω ·cm is obtained when the sample is treated at 1200 ℃ for 2 h with the surface concentration of the copper dopant source being 1.83 × 10 -7 mol/cm 2 . The copper doped n-type silicon material presents a negative temperature-sensitive characteristic and the B values are about 3010-4130 K.

Enhancing the photoluminescence intensity of CaTiO3:Eu3+ red phosphors with magnesium

Abstract Red phosphors Mg x Ca 1– x TiO 3 :Eu 3+ (0 x 2+ concentration was about 40 mol.%. It could readily be seen that the strongest PL emission was located at 617 nm monitored at 398 nm, which well matched with the near ultraviolet (NUV, 395–400 nm) GaN-LEDs. More importantly, PL emission intensity (617 nm) of phosphor Mg 0.4 Ca 0.6 TiO 3 :0.03Eu 3+ was 4.26 times of that of phosphor CaTiO 3 :0.03Eu 3+ . Based on these results, it implied that the PL intensity of phosphorCaTiO 3 :0.03Eu 3+ could be significantly enhanced by introducing Mg 2+ into CaTiO 3 host lattices and the phosphor Mg 0.4 Ca 0.6 TiO 3 :0.03Eu 3+ might be the promising red-emitting phosphor in making tricolor phosphor converted white-LEDs.

Enhancing the water-resistance stability of CaS:Eu2+,Sm2+ phosphor with SiO2-PMMA composite coating

This work was aimed at improving the water-resistance stability of CaS:Eu2+,Sm2+ phosphor. An organic-inorganic composite coating method was adopted in order to obtain ideal phosphor. The phosphor was coated with SiO2 via sol-gel technique and it was also covered by polymethyl methacrylate (PMMA) via dissolution-cohesion technique. Powder X-ray diffraction (XRD) patterns, fluorescence spectroscopy and transmission electron microscopy (TEM) were employed to characterize the phase structures, emission spectrum and surface morphologies, respectively. In addition, the water-resistance stability of the phosphor was tested by soaking the phosphor into deionized water. The results showed that the phase structures remained the same as the uncoated phosphor and the position of the fluorescence peak did not shift after surface treatment. Results showed that the water-resistance stability of the phosphor was improved to some degree. Moreover, the photoluminescence (PL) intensity of the coated phosphors reduced less than 10% of the original phosphors. Though being soaked into deionized water for 50 h, the phosphor coated with 10 wt.%SiO2-10 wt.%PMMA retained 85.9% PL intensity compared to that of the uncoated phosphor. Therefore, it could be concluded that the 10 wt.%SiO2-10 wt.%PMMA composite coating effectively improved the phosphor water resistance and retained its good optical properties.

Optically stimulated luminescence dosimeter based on CaS:Eu,Sm

Alkaline earth sulfides (MgS, CaS and BaS) crystal doped with rare-earth ions is an optically stimulated luminescence dosimeter with very high sensitivity, short time constant of the optically stimulated luminescence (OSL) separated perfectly from the stimulation. In this paper, an OSL dosimeter is described. It has linear dose response from 0.01 to 1000 Gy. The equipment, relatively simple and small in size is promising for applications in space exploration and for high dose irradiation and dangerous irradiation conditions.

A Novel Radiation Dosimetry Based on Optically Stimulated Luminescence

A new generation of Alkaline earth sulfides (MgS, CaS, and BaS) doped with rare-earth ions have been identified by the University of Montpellier as the very high sensitivity of these phosphors, the short time constant of the luminescence and the perfectly separated spectra enable many applications in real time and online dosimetry. The online detecting technology of optically stimulated luminescent (OSL) radiation dosimeter main make use of the OSL characteristics of doping the alkaline-earth metal sulphides, makes the material into the thin films for storing energy from Ionizing radiation, the excitation light through optical fibers reached the where under radiation-field, with a sensitive detection device to read out the radiation dose from storing the OSL material, obtains a novel technology of radiation dose measurement. In the previous works, the dosimeter benefits from a printed circuit board mount. Both the sensor and the electronics are exposed to radiation, the problem of the radiation induced damage is supposedly being addressed. In both cases, the use of optical fibers can provide an elegant solution. Optical fibers offer a unique capability for remote monitoring of radiation in difficult-to-access and hazardous locations. Optical fiber can be located in radiation hazardous areas and optically interrogated from a safe distance. Hence, optical fiber dosemeters are immune to electrical and radio-frequency interference that can seriously degrade the performance of remote electronic dosimeters. In this paper, a novel remote optical fiber radiation dosimeter is described. The optical fiber dosimeter takes advantage of the charge trapping materials CaS:Ce, Sm and SrS:Eu, Sm that exhibit optically stimulated luminescence (OSL). The range of the dosimeter is from 0.01 to 1000Gy. The optically stimulated luminescent (OSL) radiation dosimeter technically surveys a wide dynamic measurement range and a high sensitivity. The equipment is relatively simple and small in size, and has low power consumption. This device is suitable for measuring the space radiation dose; it also can be used in high radiation dose condition and other dangerous radiation occasions.Copyright