Principal and secondary luminescence lifetime components in annealed natural quartz

Time-resolved luminescence spectra from quartz can be separated into components with distinct principal and secondary lifetimes depending on certain combinations of annealing and measurement temperature. The influence of annealing on properties of the lifetimes related to irradiation dose and temperature of measurement has been investigated in sedimentary quartz annealed at various temperatures up to $900{}^{\circ }\mathrm{C}$. Time-resolved luminescence for use in the analysis was pulse stimulated from samples at 470 nm between 20 and $200{}^{\circ }\mathrm{C}$. Luminescence lifetimes decrease with measurement temperature due to increasing thermal effect on the associated luminescence with an activation energy of thermal quenching equal to $0.68\pm 0.01\mathrm{eV}$ for the secondary lifetime but only qualitatively so for the principal lifetime component. Concerning the influence of annealing temperature, luminescence lifetimes measured at $20{}^{\circ }\mathrm{C}$ are constant at about $33\mathrm{\mu }\mathrm{s}$ for annealing temperatures up to $600{}^{\circ }\mathrm{C}$ but decrease to about $29\mathrm{\mu }\mathrm{s}$ when the annealing temperature is increased to $900{}^{\circ }\mathrm{C}$. In addition, it was found that lifetime components in samples annealed at $800{}^{\circ }\mathrm{C}$ are independent of radiation dose in the range 85–1340 Gy investigated. The dependence of lifetimes on both the annealing temperature and magnitude of radiation dose is described as being due to the increasing importance of a particular recombination centre in the luminescence emission process as a result of dynamic hole transfer between non-radiative and radiative luminescence centres.     

222Rn concentrations of water in the Balaton Highland and in the southern part of Hungary,and the assessment of the resulting dose

In this study the ²²²Rn concentration of mains water in 120 settlements in Hungary (Southern Hungary, the Balaton Highland region) was measured. The average ²²²Rn concentration was 5.56 $(0–24.3)\mathrm{Bq}{\mathrm{l}}^{-1}$. On the basis of the ²²²Rn concentration of mains water inspected in the Southern Great Plain region, it can be stated that the ²²²Rn concentration of mains water here is, as an average, half of the ²²²Rn concentration of fountains in the same region. This decrease in radon probably happens during the water management and storage of mains drinking water. The ²²²Rn concentration of spring-water examined in the region of the Balaton Highland exceeds the average ²²²Rn concentration of drinking water (average $27.1\mathrm{Bq}{\mathrm{l}}^{-1}$).The radiation dose originating from the consumption of mains drinking water in case of adults does not reach the value of $0.1\mathrm{mSv}{\mathrm{year}}^{-1}$, even as a conservative assessment ($1\mathrm{l}{\mathrm{day}}^{-1}$ water consumption and ${10}^{-8}\mathrm{Sv}{\mathrm{Bq}}^{-1}$ dose conversion factor).     

Aspartame tablets—gamma dose response and usability for routine radiation processing dosimetry using spectrophotometry

Aspartame tablets were studied for gamma dose response, using spectrophotometric read-out method. The optimum concentration for ferrous ions was $2\times {10}^{-4}\mathrm{mol}{\mathrm{dm}}^{-3}$ and xylenol orange with $2.5\times {10}^{-1}\mathrm{mol}{\mathrm{dm}}^{-3}$ of sulphuric acid for the optimum acidity in FX solution. Wavelength of maximum absorbance is 548 nm. Post-irradiation stability is appreciable i.e. for not less than one month. Dose response is non-linear with third order polynomial fit, in the dose range of 1000–10000 Gy. This system of aspartame was further used for carrying out relative percentage dose profile measurement in Gamma Cell-220. Results obtained were inter-compared with that of a glutamine dosimeter, which showed that maximum difference between the values of aspartame and glutamine systems is within $\pm 10\%$.     

Neutron induced alpha radiography

A radiography technique which makes use of $\alpha$-particles as penetrating radiation has been developed. The images were registered in the solid-state nuclear track detector CR-39 and the conditions to obtain the best radiography image were 2.2 h of irradiation and 25 min of etching in a KOH (30%) aqueous solution at $70{}^{\circ }\mathrm{C}$. For such conditions the resolution in the image was $23\mathrm{\mu }\mathrm{m}$. Some radiographs are shown and demonstrate the potential of the technique to inspect samples with thickness in the $\mathrm{\mu }\mathrm{m}$ range.     

Pressure dependence of negative thermal expansion in Zr2(WO4)(PO4)2

Negative thermal expansion materials can experience significant stresses when they are used in composites. Under ambient conditions Zr₂(WO₄)(PO₄)₂ displays anisotropic negative thermal expansion (NTE) (${\alpha }_v=?14.0\left(10\right)\times 10^{?6}{K}^{?1}$, ${\alpha }_a=?7.9\left(5\right)\times 10^{?6}{K}^{?1}$, ${\alpha }_b=2.5\left(5\right)\times 10^{?6}{K}^{?1}$, ${\alpha }_c=?8.7\left(2\right)\times 10^{?6}{K}^{?1}$ at 0 GPa). The effect of hydrostatic pressure on its thermal expansion characteristics was investigated by neutron diffraction between 300 and 60 K at pressures up to 0.3 GPa. No phase transitions were observed in the pressure and temperature range examined. The material was found to have a bulk modulus, B₀, of 61.3(8) GPa at ambient temperature, and unlike some other NTE materials, pressure had no detectable effect on thermal expansion (${\alpha }_v=?14.2\left(8\right)\times 10^{?6}{K}^{?1}$, ${\alpha }_a=?7.9\left(3\right)\times 10^{?6}{K}^{?1}$, ${\alpha }_b=2.9\left(5\right)\times 10^{?6}{K}^{?1}$, ${\alpha }_c=?9.2\left(2\right)\times 10^{?6}{K}^{?1}$ at 0.3 GPa).     

Electric field and temperature dependence of hole mobility in electroluminescent PDY 132 polymer thin films

The current density–voltage ($J\text{–}V$) behavior of polymer PDY 132 thin films has been investigated in hole-only device configuration, viz., ITO/poly(ethylene-dioxthiophene):polystyrenesulphonate (PEDOT:PSS)/PDY 132/Au, as a function of polymer (PDY) film thickness (150 nm and 200 nm) and temperature (290–90 K). Hole current density was found to follow two distinct modes of conduction, (i) low electric field region I: ohmic conduction where slope $～1$, and (ii) intermediate and high electric field region II: non ohmic conduction where slope $～2$. Region I has been attributed to the transport of intrinsic background charge carriers while region II has been found to be governed by space charge limited currents (SCLC) with hole mobility strongly dependent on electric field and temperature. The respective hole transport parameters determined from the SCLC regime, ${\mu }_{p0}$ is $3.7\times 10^{?3}{m}^2/Vs$, ${\mu }_p(0,T)$ is $3.7\times 10^{?8}{m}^2/Vs$, and zero field activation energy (${\Delta }_0$) of 0.48 eV is obtained.     

Luminescent, optical and color properties of natural rose quartz

Rose quartz is an interesting mineral with numerous impurities that have been studied by scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), cathodoluminescence (CL), ion beam luminescence (IBL), radioluminescence (RL), thermoluminescence (TL) and optical absorption (OA). After HF etching, rose quartz from Oliva de Plasencia (Caceres, Spain) shows under SEM the presence of other silicate phases such as dumortierite $[{\mathrm{Al}}_{6.5-7}({\mathrm{BO}}_3)({\mathrm{SiO}}_4{)}_3(\mathrm{O},\mathrm{OH}{)}_3]$. The OA spectrum of rose quartz suggests that these inclusions are the cause of coloration of rose quartz. The luminescence (CL, IBL, RL, TL) spectra behavior, at both room temperature and lower, confirms that the $\sim 340\mathrm{nm}$ emission could be associated with Si–O strain structures, including non-bridging oxygen or silicon vacancy–hole centers; the observed $\sim 400\mathrm{nm}$ emission could be associated with recombination of a hole trapped adjacent to a substitutional, charge-compensated aluminum alkali ion center; the $\sim 500\mathrm{nm}$ emission could be associated with substitutional ${\mathrm{Al}}^{3+}$ and the $\sim 700\mathrm{nm}$ peak could be associated with ${\mathrm{Fe}}^{3+}$ point defects in ${\mathrm{Si}}^{4+}$ sites. These results suggest that, while defect properties of rose quartz are not greatly dissimilar to those of purer forms of quartz and silica, further research seems necessary to determine criteria for the evolution of the newly-formed self-organized microstructures in the rose quartz lattice under irradiation.     

Radon in water from Transylvania (Romania)

Radon is a radioactive noble gas of a natural origin that may be found anywhere in soil, air and in different types of water: surface, well and spring. It is worth to carry out surveys for the radon in natural waters for radiation protection as well as for geological considerations. The results present here are from a survey carried out in the Transylvania region in Romania for radon concentrations in natural waters. The measurements were made using the LUK-VR system that is based on radon gas measurement with Lucas cell. Due to the large number of water samples (1511 samples) collected for analysis, a short counting time had to be used, so that the measurements were made during the non-equilibrium state between radon and its progeny. The results show that the radon concentrations are within the range of $0.5–129.3\mathrm{kBq}/{\mathrm{m}}^3$ with an average value of $15.4\mathrm{kBq}/{\mathrm{m}}^3$ for all types of water covered within this survey.     

Persistent luminescence and synchrotron radiation study of the Ca2MgSi2O7:Eu2+,R3+ materials

The tetragonal ${\mathrm{Ca}}_2{\mathrm{MgSi}}_2{\mathrm{O}}_7$:${\mathrm{Eu}}^{2+},{\mathrm{R}}^{3+}$ persistent luminescence materials were prepared by a solid state reaction. The UV excited and persistent luminescence was observed in the green region centred at 535 nm. Both luminescence phenomena are due to the same ${\mathrm{Eu}}^{2+}$ ion occupying the single ${\mathrm{Ca}}^{2+}$ site in the host lattice. The ${\mathrm{R}}^{3+}$ codoping usually reduced the persistent luminescence of ${\mathrm{Ca}}_2{\mathrm{MgSi}}_2{\mathrm{O}}_7$:${\mathrm{Eu}}^{2+}$, which differs from the ${\mathrm{M}}_2{\mathrm{MgSi}}_2{\mathrm{O}}_7$:${\mathrm{Eu}}^{2+}$ $(\mathrm{M}=\mathrm{Sr},\mathrm{Ba})$ and ${\mathrm{MAl}}_2{\mathrm{O}}_4$:${\mathrm{Eu}}^{2+}$ $(\mathrm{M}=\mathrm{Ca},\mathrm{Sr})$ materials. Only the ${\mathrm{Tb}}^{3+}$ ion enhanced slightly the persistent luminescence. With the aid of synchrotron radiation, the band gap energy of ${\mathrm{Ca}}_2{\mathrm{MgSi}}_2{\mathrm{O}}_7$:${\mathrm{Eu}}^{2+}$ was found to be about 7 eV that is very similar to those of the ${\mathrm{M}}_2{\mathrm{MgSi}}_2{\mathrm{O}}_7$:${\mathrm{Eu}}^{2+}$ $(\mathrm{M}=\mathrm{Sr},\mathrm{Ba})$ materials. Thermoluminescence results suggested that the ${\mathrm{R}}^{3+}$ ions might act as electron traps, but only the TL peaks created by ${\mathrm{Tm}}^{3+}$ and ${\mathrm{Sm}}^{3+}$ can be found in the temperature range accessible. Lattice defects (e.g. oxygen vacancies) are also important, since the same main thermoluminescence peak was observed at about $100{}^{\circ }\mathrm{C}$ with and without ${\mathrm{R}}^{3+}$ codoping.     

Table-like magnetocaloric effect and enhanced refrigerant capacity in crystalline Gd55Co35Mn10 alloy melt spun ribbons

Gd₅₅Co₃₅Mn₁₀ ribbons were prepared by melt-spinning and subsequent crystallization treatment. Crystallization resulted in the precipitation of the Gd₃Co-type and Gd₁₂Co₇-type phases in the amorphous matrix. Under a magnetic field change of 0–5 T, a table-like magnetocaloric effect, with a maximum magnetic entropy change ${(?\mathrm{\Delta }{S}_{\mathrm{M}})}^{\max }$ of $5.46\text{J}{\text{kg}}^{?1}{\text{K}}^{?1}$ in the temperature range of 137–180 K and enhanced refrigerant capacity (RC) of $536.4\text{J}{\text{kg}}^{?1}$, was achieved in Gd₅₅Co₃₅Mn₁₀ ribbons crystallized at 600 K for 30 min. The table-like ${(?\mathrm{\Delta }{S}_{\mathrm{M}})}^{\max }$ feature and enhanced RC values make Gd₅₅Co₃₅Mn₁₀ crystallized ribbons promising for Ericsson-cycle magnetic refrigeration in the temperature range from 137 to 180 K.     

Lattice dynamics and phase transition of NiTi alloy

We have performed detailed first-principles calculations to investigate the structural and lattice dynamical properties of NiTi alloy. The calculated static structures consist well with the experimental data and other theoretical results. With quasi harmonic approximation, the phase boundary between B19′ and BCO phases can be described as a five order polynomial $T=100?89.28P+296.75P^2?717.94P^3+734.62P^4?274.25P^5$. The change of vibrational entropy is $0.07k_B$/atom at the transition temperature 100 K under zero pressure.     

Thermoluminescence properties of copper doped zirconium oxide for UVR dosimetry

The synthesized ${\mathrm{ZrO}}_2$:Cu particles were characterized using X-ray diffraction (XRD) to determine the nanocrystallite size and crystal structure, respectively. The ${\mathrm{ZrO}}_2$:Cu powder with a crystallite size of 30–40 nm has a monoclinic structure and exhibit a thermoluminescent (TL) glow curve with two peaks centered at 130 and $180{}^{\circ }\mathrm{C}$. The TL response of ${\mathrm{ZrO}}_2$:Cu as a function of wavelength exhibited two maxima at 260 and 290 nm. The TL response of ${\mathrm{ZrO}}_2$:Cu as a function of the UV light spectral irradiance was linear in the range from 10 to $2300\mathrm{mJ}/{\mathrm{cm}}^2$. Fading and reusability of the phosphor were also studied. The results showed that ${\mathrm{ZrO}}_2$:Cu nanopowder has potential to be used as a UV dosimeter in UV radiation monitoring.     

Thin film semiconductor nanomaterials and nanostructures prepared by physical vapour deposition: An atomic force microscopy study

Amorphous/nanocrystalline ${\mathrm{SiO}}_x/\mathrm{CdSe}$, ${\mathrm{GeS}}_2/\mathrm{CdSe}$, ${\mathrm{SiO}}_x/\mathrm{ZnSe}$ and $\mathrm{Se}/\mathrm{CdSe}$ amorphous multilayers (MLs) were grown by consecutive physical vapour deposition of the constituent materials at room substrate temperature. A step-by-step manner of deposition was applied for the preparation of each layer ($2–10\mathrm{nm}$ thick) of MLs. Surface morphology has been investigated by atomic force microscopy (AFM) in order to get information about ML interfaces. For a scanned area of $3.4\times 4\mathrm{\mu }{\mathrm{m}}^2$ ${\mathrm{SiO}}_x/\mathrm{CdSe}$ and ${\mathrm{GeS}}_2/\mathrm{CdSe}$ MLs showed surface roughness which is around three times greater than the roughness of ${\mathrm{SiO}}_x/\mathrm{ZnSe}$ MLs. This observation has been connected with effects of both film composition and deposition rate. For a scanned area of $250\times 250{\mathrm{nm}}^2$ the roughness determined in all MLs displayed close values and a similar increase with the ML period. The latter has been related to the flexible structure of amorphous materials. The AFM results, in good agreement with previous X-ray diffraction and high resolution electron microscopy data, indicate that the application of step-by-step physical vapour deposition makes possible fabrication of various amorphous/nanocrystalline MLs with smooth interfaces and good artificial periodicity at low substrate temperatures.