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It is well known that the luminescence efficiency of single crystals is affected by external parameters, such as the environmental temperature, especially in harsh environments. Due to this, it is of worth to examine the influence of temperature on the luminescence output of single-crystal scintillators. In this study lutetium aluminum garnet (Lu3Al5O12:Ce-LuAG:Ce) was examined, against previously published data for cadmium tungstate (CdWO4) and calcium fluoride doped with europium (CaF2:Eu) single crystals. Experiments were carried using a medical X-ray source, set to fixed high voltage (90kVp) and tube current/exposure time product (63mAs), in order to record the produced light, under different temperature conditions (20-120 Celsius). An interesting finding is that temperature, in the examined range, appear to have minimal influence on the light output of LuAG:Ce, in the contrary to the previously examined crystals (CdWO4 and CaF2:Eu) where the luminescence output constantly decreased with increasing temperature. The thermal stability of LuAG:Ce, in the examined temperature range, renders it a good choice, besides medical imaging, also for application in harsh environments as well as for long-term operation in high power LEDs.

Radiation-based imaging systems comprise multiple radiation sensors that are assembled with coupled Si PIN (positive — intrinsic — negative) photodetectors and scintillators. This paper describes the fabrication and characterization of a four-channel array Si PIN photodetector for security inspection systems. The Si PIN photodetector was fabricated using conventional (CMOS) processes at the Radiation Equipment Fab. The junction depth, passivation, and anti-reflection layer of the photodetector were controlled to maximize the light detection efficiency and the signal-to-noise ratio. The spectral responsivity obtained was 0.28 A/W for the cadmium tungstate (CWO) emission at a wavelength of 475 nm. Finally, a line pattern image was acquired using the fabricated Si PIN sensor and a self-developed readout and data acquisition system. The significance of this study is it confirms the feasibility of using the developed array-type Si PIN photodetectors in radiation-based imaging systems.

Scintillators are radiation converters applied in medical imaging detectors, in applications at harsh environments, including in geophysical detectors for deep geology boreholes, non-destructive testing (NDT) in gas and oil facilities, space, marine exploration, etc. In this study the luminescence efficiency dependence of single-crystal scintillators was examined with increasing temperature. Cadmium tungstate (CdWO4) was examined against calcium fluoride doped with europium (CaF2:Eu). The dimensions of the single crystals’ samples were 10x10x10 mm3 and were irradiated using X-ray radiographic exposures (90 kVp, 63mAs) to measure the light output with temperature (22 to 128 °C). The luminescence efficiency was found in both cases maximum at the lowest examined temperature (23.06 efficiency units-E.U for CdWO4 and 22.01 E.U. for CaF2:Eu, at 22 °C-environmental). With increasing temperature, the luminescence efficiency constantly decreased for both crystals due to thermal quenching (5.32 efficiency units for CdWO4 and 4.43 for CaF2:Eu, at 128 °C). In the mid-range (50-80 °C) CdWO4 shows increased differences compared to CaF2:Eu. CdWO4 has a higher density (7.9 g/cm 3) and luminescence signal than CaF2:Eu (3.18 g/cm 3), thus it is suitable, besides medical imaging, also for operation in harsh environments.

This study reports the synthesis of copper–zinc binary oxide coupled cadmium tungstate through a simple bio-precipitation method followed by calcination at 600 °C and its adsorption application. The characterization analysis reveals that the prepared composite has low particles size (nano-range), high porosity, and functional groups on the surface. The calcination of sample at 600 °C causes some essential function groups to disappear on the surface. Prepared composite was found to be effective adsorptive material to treat Congo red dye in aqueous solution. 2.5 g L−1 dose of adsorbent could remove more than 99% Congo red dye from 10 mg L−1 solution and more than 80% Congo red dye from 60 mg L−1 aqueous solution. The maximum adsorption capacity of present adsorbent was calculated to be 19.6 mg Congo red per gram of adsorbent. Isotherms analysis suggested a physio-chemical adsorption process. Thermodynamic analysis revealed a exothermic and feasible adsorption process. Adsorption rate was well explained by pseudo second order kinetics. The rate determining step was intra-particle diffusion evaluated from the Weber-Morris plot. To assess the adsorption performance of present adsorbent for Congo red dye the partition coefficient and adsorption equilibrium capacity were compared with other adsorbents. The partition coefficient and adsorption equilibrium values for 10 mg L−1 aqueous solution were found to be approximately 83.3 mg g−1 µM−1 and 4.0 mg g−1 at 30 °C and 7.0 pH using 2.5 g L−1 adsorbent. The value of partition coefficient was found to be higher than previous reported zinc oxide coupled cadmium tungstate having partition coefficient = as 21.4 mg g−1 µM−1 at 30 °C and 7.0 pH using 2.0 g L−1 adsorbent (Fatima, B., Siddiqui, S.I., Nirala, R.K. et al., Environ. Poll. 2021, 271, 116401). These results suggested that present adsorption technology is efficient for wastewater treatment.

Cadmium tungstate (CdWO4) photocatalyst was successfully fabricated with flower like nanosheets-assembly (FNA) by modified hydrothermal method. The as-synthesized nanostructures were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), BET surface area analysis, Fourier Transform Infrared spectroscopy (FTIR) and Photoluminescence (PL). The photocatalytic degradation performance of FNA was explored for two model dyes, Congo red (CR) and methyl orange (MO), under visible light irradiation while hydrogen absorption features were also studied at three different temperatures. Slight difference in degradation rate constants is observed for CR and MO dyes i.e. 0.0262 min-1 and 0.0517 min-1 respectively. Catalyst dose concentration of 0.1g/L has shown maximum degradation efficiency for dyes. Hydrogen storage capability reaches to 1.87 wt% at 573K when CdWO4 FNA is used.

Studies on double beta decay processes in 106Cd were performed by using a cadmium tungstate scintillator enriched in 106Cd at 66% (106CdWO4) with two CdWO4 scintillation counters (with natural Cd composition). No effect was observed in the data that accumulated over 26,033 h. New improved half-life limits were set on the different channels and modes of the 106Cd double beta decay at level of limT1/2&sim, 1020&minus, 1022 yr. The limit for the two neutrino electron capture with positron emission in 106Cd to the ground state of 106Pd, T1/22&nu, EC&beta, +&ge, 2.1&times, 1021 yr, was set by the analysis of the 106CdWO4 data in coincidence with the energy release 511 keV in both CdWO4 counters. The sensitivity approaches the theoretical predictions for the decay half-life that are in the range T1/2&sim, 1021&minus, 1022 yr. The resonant neutrinoless double-electron capture to the 2718 keV excited state of 106Pd is restricted at the level of T1/20&nu, 2K&ge, 2.9&times, 1021 yr.

Background: In this study, the light output of a cadmium tungstate (CdWO4) single crystal was measured under various X-ray radiographic energies. Methods: A CdWO4 single crystal (10 &times, 10 &times, 10 mm3) was exposed to X-rays in the 50&ndash, 130 kVp range. Measurements were evaluated against published data for single crystals of equal dimensions (CaF2:Eu and Lu3Al5O12:Ce). Since the crystal was examined for application in medical imaging detectors, the emitted optical spectrum was classified with respect to the spectral compatibility of numerous commercial optical sensors. Results: The luminescence efficiency (LE) was found to constantly increase with X-ray energy and was higher than that of CaF2:Eu for energies above 90 kVp. However, the efficiency of the previously published Lu3Al5O12:Ce was found to be constantly higher than that of CdWO4. The light emitted from CdWO4 can be optimally detected by certain charge-coupled devices (CCDs), amorphous silicon photodiodes, and photocathodes. Conclusions: The high density (7.9 g/cm3) of CdWO4 and the luminescence signal of this material make it suitable for medical imaging (such as dual energy), high-energy physics or for applications of scintillators in harsh environments.

A facile synthesis of pristine and g-C3N4 loaded CdWO4 (Cadmium Tungstate) were reported and analyzed the effect of pollutants removal in wastewater. The samples were characterized and the morphology of the pristine sample showed the nanostructures with high cluster of layer formed. While adding PEG (Polyethylene glycol), the surface has exhibited less agglomeration and in g-C3N4 added sample the agglomeration was intensely reduced and nanostructures have been clearly found. Photocatalytic performance on cationic dye was investigated under visible light. The efficiency calculated for g–C3N4– CdWO4 sample was 85% for MB. The C/C0 plot gives better degradation. The kinetic study revealed pseudo first order reaction. The g–C3N4–CdWO4 sample exhibited higher “k” value which proved best efficiency on removing the pollutant. g–C3N4–CdWO4 sample will make better reduction on toxic pollutants and be a good candidate in futuristic applications. By carbon based derivates inclusion with photo active materials, the morphology and surface area was greatly improved and it enhances activity of host material and it will be the promising material for industrial applications.

An orthogonal array design (OAD) was used for optimizing the controlled and facile precipitation of cadmium tungstate nano-plates as flower-like clusters. The reaction was performed by adding cadmium ion solutions to those of tungstate. The OAD was used to optimize the influence of the concentrations of cadmium and tungstate solutions, the rate of adding the cation solution to that of the anion and the reactor temperature on the properties of the product. These effects quantitatively were evaluated through the analysis of variance (ANOVA), while it was revealed that concentration of the cation solution, flow rate and reactor temperature have considerable effects on the qualities of the product and their optimal values were hence determined. ANOVA exhibited that under the favorable experimental condition, the thickness of cadmium tungstate nanoplates will be about 21 ± 2.9 nm. The morphology and composition of the optimal product were assessed using X-ray diffraction, scanning electron microscopy, FT-IR spectroscopy, and diffuse reflectance/transmittance spectroscopy. This product was also evaluated as a photocatalyst for the photo-induced removal of methylene blue and metyl orange and the results revealed that CdWO4 can be decolorize 90 and 86% of MB and MO after 100 and 50 min, respectively.

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 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

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.

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.

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...

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.

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.

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.

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.

Lead tungstate (PbWO4) crystal scintillators are discussed as an active shield and light guides in Cd-116 double-beta decay experiment with Cadmium tungstate (CdWO4) scintillators. Scintillation properties and radioactive contamination of PbWO4 scintillators were investigated. Energy resolution of CdWO4 detector, coupled to PbWO4 light guide, was tested. Efficiency of PbWO4-based active shield to suppress background from the internal contamination of PbWO4 crystals, as well as possible contribution from radioactivity of copper shield and phototubes were calculated. Using of lead tungstate crystal scintillators as high-efficiency 4 pi active shield could allow to build sensitive 2 beta experiment (T-1/2(0 nu 2 beta) similar to 10(26) yr) to search for 0 nu 2 beta decay of Cd-116 with (CdWO4)-Cd-116 crystal scintillators. (c) 2005 Elsevier B.V. All rights reserved.

Single-crystalline CdWO4 nanorods and nanofibers are selectively prepared based on hydrothermal treatment with cetyltrimethylammonium bromide (CTAB) as capping molecule and ordinary inorganic reactant as precursors through exactly controlling the pre-treated condition. With almost uniform breadth and pointed ends, the obtained short nanorods show a relatively thick nature along [010] direction and self-assemble to an ordered structure with (001) and (010) faces, respectively, while the as-prepared nanofibers are flexible and vertically self-assemble to form woven network. The mechanism of selective preparation and self-assembly was also discussed. Both obtained nanorods and nanofibers display a very strong blue-green luminescence property at room temperature.

The LUMINEU project is a demonstrator experiment that will search for the neutrinoless double beta decay of the isotope \(^{100}\)Mo embedded in zinc molybdate (ZnMoO\(_4\)) scintillating bolometers. In this context, a zinc molybdate crystal boule enriched in \(^{100}\)Mo to 99.5 % with a mass of 171 g was grown for the first time by the low-thermal-gradient Czochralski technique. The production cycle provided a high yield (the crystal boule mass was 84 % of the initial charge) and an acceptable level—around 4 %—of irrecoverable losses of the costly enriched material. Two crystals of 59 and 63 g, obtained from the enriched boule, were tested above ground at millikelvin temperatures as scintillating bolometers. They showed a good detection performance, equivalent to that of previously developed natural ZnMoO\(_4\) detectors. These results pave the way to future sensitive searches based on the LUMINEU technology, capable of approaching and exploring the inverted hierarchy region of the neutrino mass pattern.

A cadmium tungstate crystal boule enriched in $^{116}$Cd to 82% with mass of 1868 g was grown by the low-thermal-gradient Czochralski technique. The isotopic composition of cadmium and the trace contamination of the crystal were estimated by High Resolution Inductively Coupled Plasma Mass-Spectrometry. The crystal scintillators produced from the boule were subjected to characterization that included measurements of transmittance and energy resolution. A low background scintillation detector with two $^{116}$CdWO$_4$ crystal scintillators (586 g and 589 g) was developed. The detector was running over 1727 h deep underground at the Gran Sasso National Laboratories of the INFN (Italy), which allowed to estimate the radioactive contamination of the enriched crystal scintillators. The radiopurity of a third $^{116}$CdWO$_4$ sample (326 g) was tested with the help of ultra-low background high purity germanium $\gamma$ detector. Monte Carlo simulations of double $\beta$ processes in $^{116}$Cd were used to estimate the sensitivity of an experiment to search for double $\beta$ decay of $^{116}$Cd., Comment: 24 pages, 13 figures, 3 tables, accepted for publication on Journal of Instrumentation