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The electron response and photon response of cadmium tungstate crystal (CWO) scintillation crystal have been investigated. For the photon response measurement, the 133Ba, 22Na, 137Cs and 60Co were used as radioactive sources in the energy range of 356–1332 keV. For the electron response measurement, the 137Cs source with gamma energy at 662 keV was used for the measurement of the coincidence electron energy spectra at seven scattering angles from 30° to 120°. The seven consistent electron energies were found in the range of 101.27–443.27 keV. The light yield results for both techniques showed a slight increase when gamma energy increased. Besides, for the energy resolutions and electron energy resolutions, the graph showed the relationship between the electron energy resolution and the inverse of the square root of the electron energy.

In the present work the third-order nonlinear optical (NLO) properties of the complex-oxides crystals, including nonlinear absorption (NLA) and nonlinear refraction (NLR) are performed by the Z-scan technique. The non-centrosymmetric lithium niobate (LiNbO3) and lithium tantalite (LiTaO3) and centrosymmetric cadmium tungstate (CdWO4), calcium tungstate (CaWO4) and calcium molybdate (CaMoO4) single crystals were used for experimental investigation. The main nonlinear optical parameters, such as the two-photon absorption coefficient β, the nonlinear refractive index n2 and third-order nonlinear susceptibility for all investigated crystals are evaluated at different wavelengths λ: 1064 nm and 532 nm. Herein, the influence of λ and crystal orientation of third-order NLO properties on complex-oxides crystals is discussed.

Herein, N doped graphene quantum dots-interspersed Cadmium tungstate (CdWO4) nanorods (N-GQDs-CdWO4) were synthesized via decorating the N-GQDs on the surface of CdWO4 nanorods in three steps. The morphological and structural properties of the N-GQDs-CdWO4 nanorods were thoroughly investigated by X-ray diffraction spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier Transform infrared spectroscopy, Raman spectroscopy, and ultraviolet–visible spectroscopy. Based on imaging techniques, it became clear that the N-GQDs decorated on the surface of CdWO4 nanorods formed a heterostructure. This nanocomposite exhibits enhanced photoelectrochemical performances—more than four times those of bare CdWO4. In addition, the nanocomposite's photocatalytic activity under ultra-violet light irradiation was almost six fold that of bare CdWO4. We studied the mechanism governing its exceptional performance. It indicates that the existence of a heterostructure induces a synergistic effect between the N-GQDs and CdWO4 nanorods that bolsters photoelectric performance. Our work provides a feasible method to synthesize 0D/3D nanocomposites with enhanced photoelectrochemical performances, and offers a solution to rectify current solar energy shortfalls.

In this paper, we have investigated the electronic structure and optical properties of the single crystal and two-dimensional (2D) structure of cadmium tungstate (CdWO4). This investigation includes calculation of the density of states (DOS), dielectric tensor elements and reflectivity. All the calculations have been done by full potential augmented plane waves plus local orbitals (FP-APW+lo) with Wien2k code. The calculated band gaps for the single crystal and 2D structure along [010] direction are 4.2 and 5.02 eV, respectively. The results show that in the 2D structure of CdWO4, the electron density of the surface oxygen atoms is much more than the electron density of the inside oxygen atoms. This difference in the density has the main role in the optical properties. The results of the dielectric tensor elements and reflectivity for the single crystal are in good agreement with the experimental values. The results of the dielectric tensor elements and reflectivity for the 2D structure in comparison with the single crystal have shown that the intensity and place of the calculated peaks reduced and shifted, respectively. These results can be related to the surface oxygen atoms and thickness of the 2D structure.

In this investigation, a facile precipitation route has been developed for the preparation of cadmium tungstate (CdWO4) nanoparticles by using cadmium nitrate hexahydrate and sodium tungstate dehydrate as cadmium and vanadate precursor, respectively. The effect of different capping agents such as glycine, valine, and alanine on the morphology and particle size of the products has been investigated. Facile preparation and separation are important features of this route. This work has provided a general, simple, and effective method to control the composition and morphology of cadmium tungstate in aqueous solution, which will be important for inorganic synthesis methodology. The morphology and particle size of products were investigated by scanning electron microscopy images, X-ray diffraction patterns, ultraviolet–visible and electron dispersive X-ray spectroscopy spectroscopy. The photocatalytic characteristics of as-obtained nanocrystalline cadmium tungstate were also examined by degradation of methyl orange dye as water contaminant.

Cadmium tungstate, CdWO4, is well-known semiconducting material which exhibit good photocatalytic properties but its preparation is usually carried out at very high temperature. Hardly any report is available for its preparation through green route, and its application for water treatment. Therefore, the functionalized cadmium tungstate, f-CdWO4, nanoparticles synthesis through green, environmentally benign route using Brassica rapa leave extract and sodium tungstate and cadmium iodide was objective of the present work. The formation of f-CdWO4 was confirmed from FT-IR, XRD, and TEM, SEM and UV/Visible spectroscopic techniques. The average size of the particles was 54 nm as calculated from the XRD analysis, 37.23 nm radius was determined from UV–Visible spectrum, whereas average 27 nm breadth and 120 nm length was found from TEM imaging showing rod shaped f-CdWO4 nanoparticles. The f-CdWO4 was used for removal of toxic Bismarck brown R dye from aqueous solution through adsorption and photocatalytic degradation under sun light irradiation. The coloured water containing 10 mgL−1 concentration of dye could be cleaned with 1.5 gL-1 dose of f-CdWO4 at optimum condition. The adsorption capacity of f-CdWO4 for Bismarck brown R was found to be 46.5, 49.50, and 51.54 mgg−1 at 30, 40 and 50°C, respectively. The endothermic adsorption of Bismarck brown R followed pseudo-second order kinetics. The interaction between f-CdWO4 and Bismarck brown R, on molecular level, was investigated from FT-IR studies clubbed with isotherm, kinetics, and thermodynamics. The f-CdWO4 also showed good photocatalytic degradation activity and degraded 82.70% of Bismarck brown R in 50 mL solution having 20 mgL−1 dye concentration, with 1.5 gL-1 dosage of f-CdWO4. Therefore, f-CdWO4, prepared through green route, would be efficient for water treatment through both photocatalytic and adsorption activities. Keywords: Water treatment, Bismarck Brown, F-CdWO4, Green synthesis, Adsorption

International audience; Cadmium-116 is one of the favorable candidates for neutrinoless double-beta decay ($0\nu \beta \beta $) searches from both theoretical and experimental points of view, in particular thanks to the high energy of the decay (2813.49 keV), the possibility of the industrial enrichment in $^{116}\mathrm{Cd}$ and its use in the well-established production of cadmium tungstate crystal scintillators. In this work, we present low-temperature tests of two $0.6\ \mathrm{kg} \ ^{116}\hbox {CdWO}_{{4}}$ crystals enriched in $^{116}\mathrm{Cd}$ to $82\%$ as scintillating bolometers. These detectors were operated underground, with one at the Laboratoire Souterrain de Modane (LSM) in France and the second at the Laboratorio Subterraneo de Canfranc (LSC) in Spain. The two crystals are coupled to bolometric Ge light detectors in order to register the scintillation light. The double readout of heat and scintillation enables reduction in the background in the region of interest by discriminating between different populations of particles. The main goal of these tests is the study of the crystals’ radiopurity and the detectors’ performance. The achieved results are extremely promising, in particular, the detectors demonstrate a high energy resolution (11–16 keV FWHM at 2615 keV) and a high-efficiency discrimination of the alpha background ($\sim 20 \sigma $). These results, achieved for the first time with large mass enriched $^{116}\hbox {CdWO}_{{4}}$ crystals, demonstrate prospects of the bolometric technology for high-sensitivity searches of $^{116}\mathrm{Cd}0\nu \beta \beta $ decay.

Yttrium-90 (Y-90) has attracted great attention as a therapeutic radionuclide because of higher emitted particle energy and pure beta emitter. In Y-90 bremsstrahlung imaging, NaI(Tl) and GSO detectors are widely used in detecting photon but these detectors cannot be easily applied to this imaging because of relatively low sensitivity. Among detector candidates, cadmium tungstate (CdWO 4 ) can acquire high detection efficiency due to the high density and good light yield. The purpose of this study was to evaluate the feasibility of gamma camera system with CdWO 4 detector for quantitation of Y-90 bremsstrahlung imaging using a Geant4 Application for Tomographic Emission (GATE). To evaluate performance of the imaging system, a Y-90 point source was designed in GATE simulation. These detectors using CdWO 4 , NaI(Tl), and GSO were equipped with low energy general purpose (LEGP), medium energy general purpose (MEGP), and high energy general purpose (HEGP) parallel-hole collimators. According to the results, the average sensitivities of the CdWO 4 detector with LEGP, MEGP, and HEGP were 43.76, 37.16, and 28.22 cps/MBq, respectively. In addition, the sensitivity was higher for CdWO 4 detector system than for NaI(Tl) or GSO detector systems for all parallel-hole collimator system with 55–285 keV energy window. However, differences of scatter fraction for three detectors were very similar. Our results showed that the effect and feasibility of CdWO 4 detector for Y-90 bremsstrahlung imaging can be investigated by a GATE simulation. In conclusion, the results of this study suggest that CdWO 4 detector can be achieved improved performance of Y-90 bremsstrahlung imaging.

Ultrafast pulsed laser ablation has been investigated as a technique to machine CdWO4 single crystal scintillator and segment it into small blocks with the aim of fabricating a 2D high energy X-ray imaging array. Cadmium tungstate (CdWO4) is a brittle transparent scintillator used for the detection of high energy X-rays and γ-rays. A 6 W Yb:KGW Pharos-SP pulsed laser of wavelength 1028 nm was used with a tuneable pulse duration of 10 ps to 190 fs, repetition rate of up to 600 kHz and pulse energies of up to 1 mJ was employed. The effect of varying the pulse duration, pulse energy, pulse overlap and scan pattern on the laser induced damage to the crystals was investigated. A pulse duration of ≥500 fs was found to induce substantial cracking in the material. The laser induced damage was minimised using the following operating parameters: a pulse duration of 190 fs, fluence of 15.3 J cm−2 and employing a serpentine scan pattern with a normalised pulse overlap of 0.8. The surface of the ablated surfaces was studied using scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy and X-ray photoelectron spectroscopy. Ablation products were found to contain cadmium tungstate together with different cadmium and tungsten oxides. These laser ablation products could be removed using an ammonium hydroxide treatment.

In this paper, cadmium tungstate (CdWO4) nanoparticles were synthesized via a precipitation method based on the reaction between cadmium nitrate hexahydrate and sodium tungstate dihydrate in water. Besides, three surfactant agents such as sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, and polyethylene glycol were used to investigate their effects on the morphology and particle size of CdWO4 nanoparticles. According to the vibrating sample magnetometer, cadmium tungstate (CdWO4) nanoparticles indicated a ferromagnetic behavior at room temperature. To evaluate the catalytic properties of nanocrystalline cadmium tungstate, the photocatalytic degradations of methyl orange under ultraviolet light irradiation were carried out. The structural, morphological, magnetic, and optical properties of as—obtained products were characterized by techniques such as XRD, SEM, EDX, VSM, and UV–Vis spectroscopy.

Radiation hardness is an important property to examine in scintillators to help determine their expected lifetime in application cases where significant radiation dose is expected. Industrial imaging systems using 9 MV linear accelerators for x-ray radiography are one such application where significant radiation doses are expected to the scintillators used. Cadmium tungstate scintillators (CWO) and Thallium doped Cesium Iodide scintillators (CsI(Tl)) are used in some high energy cargo x-ray radiography systems. However, CWO has a high manufacturing cost for adequately uniform crystals and CsI(Tl) does not have sufficient radiation hardness. LKH-5 glass is being investigated as a potential low cost replacement for CWO and CsI(Tl). In this experiment 36 samples of a terbium doped silicate glass called LKH-5 were irradiated at doses up to 5 MRad using a 9 MV linear accelerator, and the change in their transmission properties was observed. The glass was discovered to be a radiation hard glass due to the relatively small change in the transmission of the glass: less than 3% per cm at its emission peak of 550 nm and 5 MRad. This is similar to CWO which has a reported reduction in transmitted light of 2% per cm at 5 MRad and the emission peak of 475 nm and better than CsI(Tl) which is reported to have a reduction in transmitted light of 5% per cm at the emission peak of 550 nm and 4.2 MRad dose. Furthermore, an annealing procedure is described that returned the transmission of the glass to pre-irradiation values.

In the present work, praseodymium-doped cadmium tungstate (Pr-CdWO4) nanoparticles were synthesized, characterized and used as catalysts in a sonocatalytic process to degrade the toxic synthetic azo dye Remazol Black B (RBB). RBB was degraded by 93.9% operating at optimal conditions (pH = 3, C = 100 mg/L, catalyst dosage = 0.35 g/L, T = 298 K and irradiation time100 min) under an ultrasonic bath at 60 kHz. Further, the addition of different radical scavengers and enhancers to the reaction was assessed. It was found that the addition of the radical scavengers sodium sulfate, sodium carbonate, and sodium chloride decreased RBB degradation from 93.9% to 86.0%, 78.0%, and 71.2%, respectively. On the contrary, the addition of the enhancers potassium periodate, peroxydisulfate and hydrogen peroxide slightly increased the RBB degradation from 93.9% to 95.3%, 96.1%, and 98.7%, respectively. The sonocatalytic process resulted in higher RBB degradation than by applying separately sonolysis (34.7%) and the catalyst as an adsorbent (39.5%). The experimental data followed both the pseudo-first-order (PFO) and Langmuir-Hinshelwood (L-H) kinetics models. However, the PFO gave better fitting (R2 = 0.993) than the L-H kinetic model (R2 = 0.9025) at the same optimum experimental conditions. The obtained results pointed out the sonocatalytic process with Pr-doped CdWO4 nanoparticles as a promising process for the degradation of azo dyes and other hazardous organic compounds existing in wastewater.

Q1. Regarding the photographic emulsion of radiographic film: A. It is made of silver halide crystals. B. The emulsion layer is coated onto a base material. C. The thickness of the emulsion is 1 mm. D. It is sensitive to radiation. E. It is sensitive to visible light.

Cadmium tungstate (CdWO4) nanoparticles were synthesized via a sonochemical method based on the reaction between cadmium(II) nitrate hexahydrate and sodium tungstate dihydrate in an aqueous solution. To the best of authors’ knowledge, it is the first time that cadmium tungstate was synthesized by ultrasonic method. The structural, morphological, and optical properties of as-obtained products were characterized by X-ray diffraction, Scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray microanalysis (EDS), and ultraviolet–visible spectroscopy. The as-synthesized cadmium tungstate indicated a ferromagnetic behavior which evidenced by using vibrating sample magnetometer at room temperature. To evaluate the photocatalysts properties of nanocrystalline cadmium tungstate, the photocatalytic degradation of methyl orange under ultraviolet light irradiation was carried out.

An experiment to search for double beta decay (2beta) decay of 106Cd with the help of a low background cadmium tungstate crystal scintillator developed from cadmium enriched in 106Cd to 66% (106CdWO4; 215 g) is in progress at the STELLA facility of the GRan Sasso underground Laboratory (INFN, Italy). The 106CdWO4 scintillator is viewed by low background PMTs through a PbWO4 crystal light guide produced from deeply purified archeological lead. The detctor operates in coincidence with the four low background HPGe to search for 2beta processes with the emission of gamma quanta. Sensitivity of the experiment after 10678 h of data taking to different channels of 2beta decay of 106Cd is on the level of limT_{1/2}=10^{19} - 10^{21} yr. In particular the limit on the T_{1/2}(2neutrinosECbeta+)>/=1.3 x 10^{21} yr at 90% C.L. reached the region of theoretical predictions.

A novel Z-scheme WO3/CdWO4 photocatalyst has been fabricated with sheet-like tungsten trioxide (WO3) hybridized by rod-like cadmium tungstate (CdWO4) via a hydrothermal and chemisorption method. The as-synthesized WO3/CdWO4 photocatalyst exhibited enhanced photocatalytic efficiency for the degradation of different organic dyes under visible light irradiation. It was found that the photocatalytic performance of the composite WO3/CdWO4 was much higher than that of either WO3 or CdWO4 for the degradation of each organic dye. The highest activity of the composite was recorded for the degradation of MB which was about 7 times greater than pure CdWO4 and 2.3 times that of pure WO3. The enhanced performance of the photocatalyst was mainly attributed to the increased surface area and introduction of WO3 into the composite sample, which can induce higher adsorption activity for organic dyes and increased electron–hole separation at the interface between two semiconductors by establishing an inner electric field.

The application of cadmium tungstate (CdWO 4 ) to a lithium-ion battery anode was firstly reported in this paper. It was prepared by a facile precipitation reaction process. The CdWO 4 sample was characterized using X-ray diffraction and scanning electron microscopy. The electrochemical properties of CdWO 4 anode were investigated. The CdWO 4 delivered a high initial discharge capacity of 2042.4 mA h g −1 . The CdWO 4 /C composite showed an improved electrochemical performance with an initial discharge capacity of 2304.1 mA h g −1 and achieved a discharge capacity of 305.1 mA h g −1 after 19 cycles. Electrochemical reaction mechanism of CdWO 4 with Li was also studied by cyclic voltammetry. It is suggested that CdWO 4 can be a promising high-capacity anode material for lithium-ion batteries.

The present paper reports synthesis and photoluminescence studies of Cadmium tungstate (CdWO4) and Cerium doped CdWO4. The phosphor samples were synthesized by low cost and low temperature hydrothermal method. The received materials are characterized by XRD, FTIR, TEM and photoluminescence (PL) studies are reported. XRD pattern reveals that the CdWO4 has monoclinic wolframite structure and the shift toward higher angle of reflection peaks suggests that the cell parameters of as-synthesized phosphor could continuously decreases and also crystallite size decreases when the Ce concentration increases. The FTIR spectrum of Cerium doped CdWO4 exhibits intrinsic bending (Cd-O) and stretching vibrations (W-O). When the pH is varied from 4 to 8 the formation of nano spheres (4 pH) nano rods (6 pH) and agglomeration as well as nano tubes (8 pH) are observed which are confirmed from TEM studies. This may be due to that formation of nano material and also the change in nature of aqueous solution from acidic to basic. When the pH changed from acidic to basic while preparing the materials the observed PL emission in the synthesized phosphor the PL intensity increases. From PL studies it suggests that more radiative traps are responsible in basic medium when compare to acidic solution and 7 nm shift in PL emission spectra observed (blue to violet region) may be due the formation of nano phosphor.

Cadmium tungstate (CdWO 4 ) nanorods have been successfully ultrafast synthesized in several minutes under enhanced microwave irradiation conditions and characterized by XRD, SEM, TEM, and photoluminescence. The products show a very strong photoluminescence peak at 475 nm with the excitation wavelength of 350 nm and a short decay time.

Cadmium tungstate (CdWO4) powders were synthesized by a hydrothermal method at different pH values. The samples show a pure monoclinic phase with the wolframite structure when they are synthesized at higher pH values. And the sample shows the highest crystallinity at a pH value of 7. All of the CdWO4 samples show the characteristic band at 788 cm−1 corresponding to symmetrical stretching vibration of W–O–W bond in WO4 2− group in Fourier transform infrared absorption spectra. The transmission electron microscope results show that the particle sizes increase with the increase of pH value, according with the results of X-ray diffraction. All synthesized CdWO4 samples show a broad blue–green emission at 350–550 nm. The emission intensity of sample synthesized at a pH value of 4 is nearly five times of that synthesized at a pH value of 1. These results indicate that the pH values have obvious influence on properties of CdWO4 crystal in the hydrothermal synthesis.

The present paper reports synthesis and photoluminescence studies of cadmium tungstate (CdWO4) and cerium-doped cadmium tungstate. The samples were synthesised by low cost and low temperature hydrothermal method and characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and photoluminescence analysis. XRD pattern reveals that the CdWO4 has monoclinic wolframite structure. The FTIR spectrum of cerium-doped CdWO4 exhibits broadband below 700 cm−1 which is due to the δ (Ce–O–C) mode. The TEM images show that size of particle is approximately 60–120 nm in both samples. A broad intense peak was observed at 474 nm when the samples were excited with 263 nm. A broad intense peak was observed at 475 nm when the samples were excited with 600 nm. The intensity of the 474 nm peak decreases with increase in cerium doping concentration. The observation of 475 nm peak when excited with 600 nm is upconversion luminescence. This upconversion emissio...

A novel cadmium and praseodymium tungstate, Cd 0.25 Pr 0.50 □ 0.25 WO 4 , and its Cd 0.25 Pr 0.50−0.25 x RE 0.25 x □ 0.25 WO 4 solid solutions (where RE = Nd or Sm, □ are cationic vacancies, and x = 0.02, 0.10, 0.20 and 1.00), have been successfully prepared by high-temperature solid-state reaction of cadmium tungstate (CdWO 4 ) with praseodymium ditungstate (Pr 2 W 2 O 9 ) or an adequate Pr 2 W 2 O 9 /RE 2 W 2 O 9 (RE = Nd, Sm) mixture. The resulting products were characterized by powder X-ray diffraction (XRD), differential thermal analysis with thermogravimetry (DTA-TG) and infrared spectroscopy (IR). The morphology of polycrystalline samples was determined using scanning electron microscopy (SEM). The Cd 0.25 Pr 0.50 □ 0.25 WO 4 tungstate and its solid solutions crystallize in the tetragonal scheelite type structure and melt congruently. The melting point of each Cd 0.25 Pr 0.50−0.25 x RE 0.25 x □ 0.25 WO 4 solid solution is slightly lower than the melting point of Cd 0.25 Pr 0.50 □ 0.25 WO 4 (1400 K). IR spectra of Cd 0.25 Pr 0.50 □ 0.25 WO 4 as well as Cd 0.25 Pr 0.50−0.25 x RE 0.25 x □ 0.25 WO 4 confirm that their crystal structure consists of WO 4 tetrahedra. Electron paramagnetic resonance (EPR) studies of Cd 0.25 Pr 0.50−0.25 x Nd 0.25 x □ 0.25 WO 4 solid solutions at low Nd 3+ ions content showed the existence of isolated Nd 3+ ions in paramagnetic state. The existence of neodymium antiferromagnetic dimers has been revealed for higher Nd 3+ ions concentrations in the solid solutions under study.

Pulsed cathodoluminescence of cadmium tungstate crystals doped with lithium and bismuth was investigated. It was shown that emission spectra of the crystals were dominated by a single band with a maximum at 2.6 eV. The luminescence decay curves of CdWO 4 , CdWO 4 :Li, and CdWO 4 :Li+Bi crystals were similar and could be described by exponential functions with τ = 13 μs at 300 K. It was found that the luminescence light yield did not vary substantially after adding dopants.

The logging and characterization of geothermal wells requires improved scintillator systems that are capable of operation at temperatures significantly above those commonly encountered in the logging of most conventional oil and gas wells (e.g., temperatures nominally in the range of up to 150 °C). Unfortunately, most of the existing data on the performance of scintillators for radiation detection at elevated temperatures is fragmentary, uncorrelated, and generally limited to relatively low temperatures—in most cases to temperatures well below 200 °C. We have designed a system for characterizing scintillator performance at temperatures extending up to 400 °C under inert atmospheric conditions, and this system is applied here to the determination of scintillator performance at elevated temperatures for a wide range of scintillators including, among others: bismuth germanate, cadmium tungstate, cesium iodide, cesium iodide (Tl), cesium iodide (Na), sodium iodide, sodium iodide (Tl), lutetium oxy-orthosilicate (Ce), zinc tungstate, yttrium aluminum perovskite (Ce), yttrium aluminum garnet (Ce), lutetium aluminum perovskite (Ce), and barium fluoride, strontium iodide (Eu). Most of the scintillator samples exhibited severe degradation in light yield at elevated temperatures. Measurements were terminated at temperatures at which the measured light yield no longer appeared useful. The results of these high-temperature scintillator performance tests are described in detail here. Comparisons of the relative elevated-temperature properties of the various scintillator materials have resulted in the identification of promising scintillator candidates for high-temperature use in geothermal and fossil-fuel well environments.

Eu3+ doped CdWO4 nanorods, with nearly uniform nanoscale was synthesized via a novel simple hydrothermal method easy for commercial run at 160 °C, of which the average dimensions are about 250, 50 and 20 nm in length, width and height respectively from the result of transmission electron microscopy (TEM). Powder X-ray diffraction (PXRD) pattern shows the product is pure wolframite structure. Different from undoped products showed brilliant blue-green irradiation and block crystals with multi-emission bands in red light range, the Eu doped nanorods give preferred strong 5D0→7F2 transition and are excellent red phosphor with high color purity supported by the photoluminescent (PL) measurements and ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS). This suggests that a combination of the Eu3+ doped and undoped products are potential to realize the white lighting LED with blue, green and red components.

This study comprises a continuation of the previous efforts of the authors to characterize different sources of errors in phosphor thermometry based on the determination of luminescence decays from thermographic phosphors. Whereas earlier investigations focused on point detectors utilizing different sensor technology, this work presents a comparison of four PMTs that are identical in terms of their product type. These detectors are supposedly identical, but the investigations revealed that their response is strictly individual. This study also shows a linear excitation energy dependence for the decay time of cadmium tungstate (CdWO4), the phosphor being used in this work. In addition, the potential influence of the intense and short fluorescence peak preceding the weaker and longer exponential decay in some phosphor materials was investigated using the electrical signal gating capability of the PMT. Finally, the evaluated decay time also appeared to be affected by the oscilloscope settings used when recording the phosphorescence signals. The presented results indicate that all operating parameters from the calibration measurement need to be rigorously reproduced in order to avoid systematic temperature errors in phosphor thermometry experiments that are based on reproducible measurements of the decay time. These results should be of more general interest also outside the phosphor community as the findings, presented herein, in principal concern all kinds of measurements that are dependent on reproducible measurements of signal shapes or time transients.

This work demonstrates the possibility of synthesis of cadmium tungstate at low temperatures using oxide precursors. Cadmium tungstate (CdWO4) scintillator was produced via microwave-assisted hydrothermal reaction using the precursors CdO and WO3. The methodology was based on microwave radiation for heating, which is remarkably faster than the solid-state route or conventional hydrothermal procedure. CdWO4 monoclinic (wolframite) structure was successfully obtained at 120°C for synthesis times as short as 20 min. This route does not require the use of templates or surfactants and yields self-assembled nanorods with size of around 24 ± 9 nm width and 260 ± 47 nm length. The growth mechanism for the formation of CdWO4 involves microwave-induced dissociation of the reagents and solvation of Cd2+ and WO42- ions, which are free to move and start the nucleation process. The luminescence properties of the produced nanoparticles were investigated, presenting a broad emission band at around 500 nm, which is comparable to that observed for samples produced using other chemical routes. This result highlights the great potential of the proposed method as a low-cost and time saving process to fabricate luminescent oxide nanoparticles.

A radiopure cadmium tungstate crystal scintillator, enriched in 106 Cd to 66%, with mass of 216 g (106CdWO4) was used in coincidence with four ultra-low background HPGe detectors contained in a single cryostat to search for double beta (2β) decay processes in 106 Cd. New improved half-life limits on the 2β processes in 106 Cd have been set on the level of 1020 — 1021 yr after 13085 h of data taking deep underground (3600 m w.e.) at the Gran Sasso National Laboratories of INFN (Italy). In particular, the limit on the two neutrino electron capture with positron emission, Teβ+2 1/2≥ 1.1 × 1021 yr, has reached the region of theoretical predictions. The resonant neutrinoless double electron captures to the 2718, 2741 and 2748 keV excited states of 106 Pd are restricted on the level of T2e0v 1/2 ≥ (8.5 × 1020 - 1.4 × 1021) yr.

Experiments to search for neutrinoless double beta decay are considered as an unique tool to study properties of neutrino and weak interactions. Scintillation detectors possess important properties required for high-sensitivity double beta decay experiments: presence of elements of interest, low level of intrinsic radioactivity, reasonable spectrometric characteristics, fast response, pulse-shape discrimination ability. Moreover, some crystal scintillators can be applied as cryogenic scintillating bolometers with high energy resolution and excellent particle discrimination. High concentration of isotope of interest and as low as possible radioactive contamination are important requirements to a scintillation material to be used in double beta decay experiments. Therefore development of radiopure crystal scintillators from isotopically enriched materials is required. Other important issues are maximal output of detectors and minimal loss of enriched materials. High quality, radiopure cadmium tungstate crystal scintillators were developed from enriched 106Cd and 116Cd, while calcium molybdate scintillators were grown form calcium depleted in 48Ca and molybdenum enriched in 100Mo. Prospects of several scintillation materials, promising for double beta experiments, are discussed.

Besom-like CdWO 4 structures composed of single-crystalline nanorods were prepared by hydrothermal process with a wide range of pH, without the assistance of any template. The phase composition, crystal structure and morphology of final product were characterized by XRD, SEM and TEM. The obtained results revealed that with increasing the pH of synthesizing solution the size of besom-like CdWO 4 structures composed of single-crystalline nanorods has become larger. The nanorods in the sample synthesized at pH = 11 have widths of ∼50 nm and lengths of

Two technologically important materials – cadmium tungstate CdWO4 and zinc tungstate ZnWO4 – are studied in details using the plane wave based first-principles calculations. The optimized crystal structures were used to calculate the electronic and optical properties of both materials. Comparison of the calculated results with the available in the literature experimental X-ray photoelectron spectra (XPS) and reflectivity spectra yielded good agreement and allowed for assignment of the experimentally observed features, including those induced by difference between the Cd 4d and Zn 3d states. In addition, the variations in the electron density distributions related to two crystallographically in equivalent oxygen positions were revealed.

The possibility of zinc and cadmium tungstate synthesis by reaction of metal nitrates with ammonium paratungstate by microwave irradiation is studied. Formation of the metal tungstate begins in a liquid phase at the melting point of initial hydrates and is completed at their complete decomposition temperature, at 400-450°C. The microwave activation does not have influence on the mechanism of cadmium and zinc tungstate synthesis, but it considerably accelerates it. It is shown that, during the microwave activation, cadmium tungstate, with scheelite structure (a = 5.170 A, c = 11.140 A), is formed.

Tungstate crystals are considered high-class scintillators to be used as detector material for high-energy radiation. These crystals are frequently used as references in measurements on new luminescent materials. In this paper, we present manufacturing process of nanocrystalline tungstate materials. Lead tungstate (PbWO4), cadmium tungstate (CdWO4), calcium tungstate (CaWO4), and zinc tungstate (ZnWO4) were synthesized via modifying sol-gel process. An advantage of the developed technology is the possibility of manufacturing tungstate powders in nanocrystalline state not only at elevated temperatures but at room temperatures as well. X-ray diffraction method, scanning electron microscopy, and thermal investigations were done to establish structural and morphological state of these materials. For reaching the most dispersible with the lowest agglomeration single-phase system of tungstate materials, there was an established optimal relationship between the system of starting reagents and solvents.

A new group of cadmium and rare-earth metal molybdato–tungstates with the formula Cd0.25 RE 0.50□0.25(MoO4)0.25(WO4)0.75 (RE = Pr, Nd, Sm–Dy, □—vacancies in cation sublattice) were synthesized by a high-temperature solid-state reaction between RE 2MoO6 and CdWO4 mixed at the molar ratio of 1:3. Powder X-ray diffraction measurements showed that obtained phases adopt the scheelite-type structure. The phases melt congruently in the temperature range of 1382–1458 K.

A cadmium tungstate crystal scintillator enriched in 106 Cd was developed for an experiment to search for double beta processes in 106 Cd. With this aim samples of cadmium with natural isotopic composition and enriched in 106 Cd were purified by vacuum distillation. Cadmium tungstate compounds were synthesized from solutions. The absolute isotopic composition of the enriched cadmium was accurately determined as 66.4% by thermal ionisation mass-spectrometry. A 106 CdWO 4 crystal boule was grown by the low-thermal-gradient Czochralski technique. The total irrecoverable loss of the enriched cadmium in all the stages of the crystal scintillator production does not exceed 2.3%. The produced 106 CdWO 4 crystal scintillator with mass of 216 g exhibits good optical and scintillation properties.

Results are reported on the effects of gamma-radiation upon scintillation characteristics of CdWO 4 (CWO) single crystals with different defects. The defect structure before irradiation determines the radiation-induced changes of the CWO crystals. Radiation effects in CWO crystals were shown to be related to the formation of F-centers. In some CWO samples, the dose of 103 Gy caused destruction of defects responsible for induced absorption. Doping by Li leads to reduction of defects responsible for color and trapping centers in CWO crystals. The annealing in a reductive medium (H 2 ) or doping with Me3+ significantly increases radiation stability of CWO.

Cadmium tungstate (CdWO4) nanorods were successfully synthesized via a hydrothermal process and characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and photoluminescent spectra techniques (PL). A pure monoclinic phase of well-crystallized CdWO4 nanorods, with lengths of 250–400 nm and widths of 30–60 nm, could be readily synthesized at as low temperature as 70 °C.The CdWO4 nanorods showed a PL emissions peak at 435 nm.