br Conclusions The exact solution

Conclusions The exact solution of the Gibbs–Tolman–König–Buff equation makes it possible to describe the relationship between the melting point and the particle sizes ranging from 3 to 20nm more adequately, which goes to further prove that surface tension forces play the decisive role in the initial phase of plastic straining of ultrafine materials. The available experimental data on the plastic-flow mesoprocesses depending on the curvature radius of nanostructural elements [17] confirm this point of view.
Introduction Solid-state luminescent dosimetry is based on radiation aldose reductase inhibitors storage in dosimetric materials in the form of lattice defects and captured charge carriers. The stored energy can be released through the light from luminescence centers. Energy release is stimulated either by heating (thermally stimulated luminescence (TSL/TL)) or by irradiating with light quanta of proper energy (optically stimulated luminescence (OSL)). TL-based dosimeters are widely used in radiation dose monitoring but in comparison to TL dosimetry technique OSL has been becoming popular in radiation dosimetry applications [1–4]. OSL has been first used in archaeological dating and later proposed for personnel monitoring and environmental monitoring of radiation with the development of Al2O3:C [5]. Different stimulation techniques have been followed by OSL measurements that offer different signal-to-noise ratio. A few of them are CW-OSL, P-OSL, LM-OSL, TA-OSL and NL-OSL, amongst which CW-OSL is the most preferred and popular choice of stimulation mode, because in CW-OSL, the luminescence is recorded very fast and looks like a decay curve, the background count rate or net background is nearly constant and signal-to-noise ratio is high [6]. Over the last several decades sulfate hosts doped with rare earth materials have been widely used in radiation dosimetry, and also these materials show good luminescent properties. Many researchers have reported on these materials with different synthesis methods and studies for different luminescence properties [7–9]. In this paper we are reporting TL and OSL properties (under beta irradiation) of Eu-doped SrSO4 phosphor synthesized by using co-precipitation.
Experimental details SrSO4 phosphor activated with Eu was prepared by the co-precipitation method described in our earlier works [10]. The stoichiometry of the reaction was maintained by the formula Sr1–SO4 : Eu2+. The nitrate precursor of strontium was dissolved in 100ml of double-distilled water with drop-wise addition of the stock solution prepared for Eu2O3. The solution was prepared in a glass beaker under stirring to form a homogeneous aqueous solution, and it was confirmed that the precursor was dissolved in distilled water. 10ml of the H2SO4 solution were added drop by drop into the mixed aqueous solution of Sr1–(NO3)2 : Eu under rigorous stirring at room temperature and white precipitation formed. After that, the SrSO4 precipitate was centrifuged and rinsed several times by distilled water to remove the excess residual salts. The precipitate was dried at 60°C for 2h by optical heating. The dried sample was annealed at 900°C for 1h to get a white crystalline powder of SrSO4:Eu2+. The complete process involved in the reaction is presented as a flow chart in Fig. 1.
Results and discussion The structure of the as-prepared samples were analyzed by a Rikagu Miniflex X-ray diffractometer, using monochromatic CuKα1 (λ=1.5405Å) radiation in the 2θ range of 10–60°. Photoluminescence was studied by means of a Hitachi F-7000 fluorescence spectrophotometer. Emission and excitation spectra were recorded using a spectral slit of 2.5nm for each window. For studying the TL and the OSL response, all the samples were irradiated using a 90Sr/90Y beta source with the dose rate of 20 mGy per minute. All OSL measurements were carried out using an automatic Risø TL/OSL-DA-15 reader system which capable of accommodating up to 48 disks. Blue-light diodes emitting at 470nm (LEDs with FWHM=20nm) were arranged in four clusters, each containing seven individual LEDs. The total power from 28 LEDs at the sample position was 80mW/cm2. A green long pass filter (GG-420) was incorporated in front of each blue LED cluster to minimize the amount of directly scattered blue light from reaching the detector system. The standard photomultiplier used in the Risø TL/OSL luminescence reader was a bialkali EMI 9235QA, which has an extended UV response with maximum detection efficiency between 300 and 400nm. To prevent scattered stimulation light from reaching the photomultiplier, the Risø reader was equipped with a 7.5mm Hoya U-340 detection filter, which has a peak transmission around 340nm (FWHM ∼80nm).