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Tungsten- and nickel-containing coatings have been produced on the surface of synthetic diamond crystals by rotary chemical vapor deposition (RCVD) using tungsten hexacarbonyl, W(CO)6, and nickelocene, Ni(C5H5)2, as gaseous precursors. The thickness, composition, and morphology of the coatings have been shown to depend on the RCVD process duration and reactant concentrations in the vapor phase. The synthetic diamond microcrystals with tungsten- and nickel-containing coatings have been used to produce copper–diamond heat-conducting composites. Powder mixtures containing 50 vol % diamond with a particle size of 50, 100, or 200 μm have been consolidated by spark plasma sintering or hot pressing. It has been shown that the highest relative density (97%) and thermal conductivity (340 W/(m K)) are offered by the composites produced by spark plasma sintering using tungsten carbide-coated 50-μm diamond crystals. more...

Garnet phosphor Y3Al5O12:Ce3+ is prepared in the Y2O3–Al metal–CeO2 ternary system by the solid-state reaction method in the air. For the first time, metal Al is used as a source of aluminum for the reaction instead of traditional oxide Al2O3. It is shown that the chemical reaction can be realized at lower temperatures and without use of special reducing atmosphere. The structural and spectroscopic properties of the prepared powder phosphor are very close to those earlier reported for the Y3Al5O12:Ce3+ single crystal. more...

Diamond/W,Cu heat-conducting composite shims were produced by the multistep route. Initially, the surface of the microdiamonds ∼200 μm in size was covered by a W/WC layer using the deposition from a vapour of tungsten carbonyl. Then, the diamond/W,Cu pills were pressed from the mixture of W/WC-covered diamonds and metal copper powder and the composite shims were sintered at 1270 K in vacuum. The thermal conductivity coefficient and coefficient of thermal expansion (CTE) measured for the diamond/W,Cu composite shims were as high as 450–650 W·m−1·K−1 and 5.5–7.5 10−6/K, respectively. more...

The Eu3+-doped red-orange emitting phosphor of tellurite glass 0.25Li2O–0.20Y2O3–0.5TeO2–0.05Eu2O3 has been synthesized by the melt quenching method. The amorphous nature of the glass has been verified by XRD measurements. The photoluminescence excitation and emission spectra, the luminescence decay curves have been investigated for the composition. The phosphor can be efficiently excited by the near UV light to realize the intense narrow red emission line (611 nm) corresponding to forced electric dipole transition 5D0 → 7F2 of Eu3+ ions. The Li2O–Y2O3–TeO2:Eu3+glass phosphor is a potential red-orange emitting candidate for the application in WLEDs. more...

In the present study, tungsten-containing coatings on diamond particles were obtained by chemical vapor deposition using tungsten carbonyl as a precursor. It was found that tungsten reacts with diamond, which results in the formation of tungsten carbide WC crystallizing along certain crystallographic directions of the diamond crystal. Morphological studies of the coated diamonds have shown that the {111} facets of diamond are more reactive than the {100} facets. more...

The crystals of zinc tungstate (ZTO) are a radiation-hardened matrix and are widely used as scintillators for high energy radiation. Therefore, it is interesting to study the possibility of introducing gadolinium ions into this structure to obtain the lasing properties. In order to activate ZTO crystals by gadolinium ions, 0.5 mol.% of Gd2O3 is added to the load. High-quality large crystals of ZTO are produced. The spectra of optical transmission, luminescence excitation, and luminescence are measured at room temperature. It is shown that the introduction of gadolinium ions does not result in a shift of the main luminescence band of the ZTO crystals. The analysis of the ESR spectra and their modeling enables the calculation of spin-Hamiltonian parameters. It is shown that the observed spectrum depends on the state of Gd3+ ions with S = 7/2 and is well described by the spin-Hamiltonian parameters g x = 1.9835, g y = 1.9685, g z = 1.9688 and D = 644.88 Gs, E = 161.49 Gs. Directions of the principal values of the D tensor are determined; they reflect a strong distortion of the nearest-neighbor oxygen environment. more...

We present a prototype scintillating bolometer for the search for neutrinoless double beta decay of Mo-100, consisting of a single a parts per thousand 5 g ZnMoO4 crystal operated aboveground in the 20-30 mK temperature range. The scintillation light is read out by two thin Ge bolometers. The phonon signals are collected by NTD Ge thermistors. The ZnMoO4 crystal was grown with an advanced method (low-thermal-gradient Czochralski technique) and after purification of molybdenum. The results are very encouraging: the intrinsic energy resolution of the heat channel is a parts per thousand 800 eV FWHM, the alpha/beta rejection factor (crucial for background suppression) is better than 99.9% in the region of interest for double beta decay (a parts per thousand 3 MeV), and the radiopurity of ZnMoO4 looks substantially improved with respect to previous devices. more...

The ZnO-MoO3 phase diagram in the range of ZnO compositions from 0.95 to 1.05 mol % is refined by differential scanning calorimetry. Data on crystal stoichiometry are obtained using the weighting method by reducing ZnMoO4 in a hydrogen atmosphere. The specific features of solid-phase synthesis of ZnMoO4 are studied, and its heat of fusion is measured. The modes of solid-phase synthesis and growth of ZnMoO4 crystals are optimized. Some experimental data on the ZnMoO4 crystal growth in the [001] direction by the low-thermal gradient Czochralski method are presented. Crystals with a cross section of ∼50 × 50 mm2, a length of 160 mm, and a weight up to 1 kg have been obtained. more...

A method for phosphors solid-phase synthesis under high pressure is proposed. Using the method, phosphors based on rare earth garnets were synthesized at a temperature considerably lower (1300 °C) than the temperature of the synthesis by conventional method (above 1650 °C). Using organic, inorganic ligaments and synthesized phosphors, remote phosphors were created. The chromaticity coordinates of created LEDs on the base of blue LEDs and remote phosphors fall into the bin of white and green colours. Luminous efficiency reaches 140 lm/W. more...

We investigate the performances of two ZnMoO4 scintillating crystals operated as bolometers, in view of a next generation experiment to search the neutrinoless double beta decay of Mo-100. We present the results of the alpha vs beta/gamma discrimination, obtained through the scintillation light as well as through the study of the shape of the thermal signal alone. The discrimination capability obtained at the 2615 keV line of Tl-208 is 8 sigma, using the heat-light scatter plot, while it exceeds 20 sigma using the shape of the thermal pulse alone. The achieved FWHM energy resolution ranges from 2.4 keV (at 238 keV) to 5.7 keV (at 2615 keV). The internal radioactive contaminations of the ZnMoO4 crystals were evaluated through a 407 hours background measurement. The obtained limit is < 32 microBq/kg for Th-228 and Ra-226. These values were used for a Monte Carlo simulation aimed at evaluating the achievable background level of a possible, future array of enriched ZnMoO4 crystals., 9 pages, 8 figures more...

Several experiments were performed during last years at underground (3600 m w.e.) Laboratori Nazionali del Gran Sasso (LNGS) of the INFN (Italy) to search for resonant 2$\varepsilon0\nu$ captures in 96Ru, 106Cd, 136Ce, 156Dy, 158Dy, 180W, 184Os, 190Pt with the help of HP Ge semiconductor detectors, and ZnWO4 and 106CdWO4 crystal scintillators. No evidence for r-2$\varepsilon0\nu$ decays was found, and only T_{1/2} limits were established in the range of 10^{14}-10^{21} yr., Comment: Proceedings of TAUP 2011 Conference more...

A search for double beta decay of 64,70Zn, 180,186W was carried out by using low background ZnWO4 crystal scintillators, while a CeCl3 scintillation detector was applied to investigate 2β processes in 136,138,142Ce. A search for 2β decay of 96,104Ru, 156,158Dy, 190,198Pt and study of 2ν2β decay of 100Mo to the first excited 0+ level of 100Ru were realized by ultra‐low background HPGe γ spectrometry. Moreover, CdWO4 crystal scintillators from enriched 106Cd and 116Cd isotopes were developed to search for 2β decay of 106Cd and 116Cd. Finally, experiments aimed to investigate 96,104Ru and 116Cd are in progress and a new phase of the experiment to search for 2β processes in 106Cd is in preparation. more...

An experiment to search for 2b processes in 106Cd with the help of 106CdWO4 crystal scintillator (mass of 215 g), enriched in 106Cd up to 66%, is in progress at the Gran Sasso National Laboratories of the INFN (Italy). After 1320 h of data taking, limits on double beta processes in 106Cd have been established on the level of 1019–1020 yr, in particular (all the results at 90% C.L.): T1/2(0ν2e)>3.6×1020 yr, T1/2(2νeβ+)>7.2×1019 yr, and T1/2(2ν2β+)>2.5×1020 yr. Resonant 0ν2e processes have been restricted as T1/2(0ν2K)>1.4×1020 yr and T1/2(0νLK)>3.2×1020 yr. A possible resonant enhancement of the 0ν2e processes is estimated in the framework of the QRPA approach. more...

Composite material with high thermal conductivity was obtained by the method of thermal sintering of diamonds (synthetic and impact) and copper powder and by further hot isostatic pressing. The content of diamond (the particle size is 20 - 250 μm) in the diamond copper composite was 30 - 45 weight percent. The coefficient of thermal conductivity of copper diamond composite materials based on synthetic diamonds was measured to be 700 - 750 Wm-1K-1. The coefficient of thermal conductivity of copper diamond composite materials based on impact diamonds was measured to be 850 - 900 Wm-1 K-1. The coefficient of thermal expansion (CTE) was measured to be 5.5 - 6.5 • 10-6/°C for synthetic diamonds and 6.1 - 6.5 •10-6/°C for impact diamonds. The obtained copper diamond composite materials are promising to be used as crystal holders for semiconductor crystals in THz and microwave devices. more...

Composite material with high thermal conductivity was obtained by the method of thermal sintering of a diamond (50 – 75%) with a size of 20 to 250 μm in a matrix of copper.Coefficient of thermal conductivity of copper diamond composite materials was measured and is 450 – 650 Wm-1K-1. The coefficient of thermal expansion CTE was measured and is 5.5 – 7.5 10-6/°C. The obtained copper diamond composite materials are promising objects for use in THz and microwave devices. more...

In the present study, W- and Ni-containing coatings on diamond crystals were obtained by rotary chemical vapor deposition (RCVD) using tungsten carbonyl W(CO) 6 and nickelocene Ni(C 5 H 5 ) 2 as precursors. Morphological features of the coatings deposited under different processing conditions were investigated. For obtaining bulk diamond-copper composites, mixtures of the coated and uncoated diamond crystals with a copper powder were subjected to Spark Plasma Sintering (SPS). The effects of the presence of the coatings on the diamond crystals and the size of the initial diamond particles on the microstructure, relative density and thermal conductivity of the consolidated diamond-copper composites were investigated. more...