[en] N-doped Cu₂O films are deposited by sputtering a CuO target in the mixture of Ar and N₂. The structures zand optical properties have been studied for the films deposited at different temperatures. It is found that N-doping can suppress the formation of CuO phase in the films. The films are highly (100) textured at low temperatures and gradually change to be highly (111) textured at the temperature of 500 deg. C. With the analysis of (111) and (100) grain sizes, the surface free energy and grain size of critical nuclei are suggested to dominate the film texture. The analysis of the atomic force microscopy shows that the film growth can be attributed to the surface-diffusion-dominated growth. The forbidden rule of band gap transition is found disabled in the N-doped Cu₂O films, which can be attributed to the occupation of 2p electrons of nitrogen at the top of valence band. The optical band gap energy is determined to be 2.52 ± 0.03 eV for the films deposited at different temperatures.

[en] HfC whiskers are obtained on graphite substrates by a catalyst-assisted vacuum chemical vapor deposition process from the HfCl₄–C₃H₆–H₂–Ar system in a reactive atmosphere containing a small amount oxygen impurity. The composition, crystallinity and morphology of the HfC whiskers are examined with energy-dispersive X-ray, X-ray diffraction, field-emission scanning electron microscopy. The influence of the element oxygen on the composition, crystallinity and morphology of the whiskers or deposits is analyzed. The results show that with the decrease of oxygen content during deposition, the quantity of HfO₂ decreases and the crystallinity of HfC crystals improve, and the deposits change from the porous HfO₂ coating covered by the HfO₂ nano-rods into the HfC whiskers with rough side faces. Small HfO₂ nano-particles grow on the surface of the HfC whiskers sporadically and dispersedly, and the sizes and quantities decrease as the O content reduces. Gibbs free energy of HfO₂ generation is analyzed using HSC chemistry^® 5.0. The results of the thermodynamic analysis confirm a small quantity of O can lead to HfO₂ generation and HfO₂ can stably exist under the reducing atmosphere with C₃H₆ and H₂ at 1573 K. - Graphical abstract: HfC whiskers with various O contents were synthesized by vacuum catalyst-assisted CVD. The composition, crystallinity and morphology of HfC whiskers changed greatly with variation of the O content. The cause of HfO₂ generation was analyzed by thermodynamic calculations. Highlights: • HfC whiskers with various O contents were synthesized by vacuum CVD. • The effects of O on the composition, crystallinity and morphology were studied. • The cause of HfO₂ generation was analyzed by thermodynamic calculations

No abstract available

[en] The Advanced GAmma Tracking Array (AGATA) has been installed at the GANIL facility, Caen-France. This set-up exploits the stable and radioactive heavy-ions beams delivered by the cyclotron accelerator complex of GANIL. Additionally, it benefits from a large palette of ancillary detectors and spectrometers to address in-beam γ-ray spectroscopy of exotic nuclei. The set-up has been designed to couple AGATA with a magnetic spectrometer, charged-particle and neutron detectors, scintillators for the detection of high-energy γ rays and other devices such as a plunger to measure nuclear lifetimes. In this paper, the design and the mechanical characteristics of the set-up are described. Based on simulations, expected performances of the AGATA $1\pi$ array are presented.

[en] Short communication

[en] Short communication

[en] Glasses in the ternary CaO-Fe₂O₃-P₂O₅ system were prepared and studied by means of density, differential scanning calorimetry, infrared, Raman and UV-Vis spectroscopies. The results showed that density and molar volume in the glass system decreased with increasing substitution of CaO for Fe₂O₃. The variation of glass transition temperature and thermal stability was strictly related to the nature of bonding in the vitreous network. Spectroscopic analysis showed that substitution of CaO for Fe₂O₃ induced an evolution of structural units from pyrophosphate to metaphosphate species indicating the polymerization of phosphate chains and the decrease of non-bridging oxygen concentrations. With increasing substitution of CaO for Fe₂O₃ The P-O-Ca linkage and (P^-O^- Ca^2+-O-P) chains participated in the glass network by replacing P-O-Fe bonds. The absorption band of the P-O-Ca stretching mode in the glasses with high CaO content (≥32 mol%) was assigned at around 1084 cm^-1. The absorption edge would fall in the region between 332 and 420 nm which are the absorption bands of Fe³⁺ ions. (author)

[en] Substitutional compounds CrSb_2-xTe_x (0 ≤ x ≤ 0.05) were synthesized and the effects of Te substitution on transport and thermoelectric properties of CrSb_2-xTe_x were investigated from 7 K to 310 K. It was established that the resistivity ρ, absolute value of thermopower |S| and thermal conductivity decrease with increasing Te content. The decrease of the resistivity ρ and absolute value of thermopower |S| could be mainly explained by an increase in electron concentration due to Te substitution for Sb, while the decrease of thermal conductivity of CrSb_2-xTe_x could be caused by the enhancement of phonon scattering by the dopant. Besides, it was discovered that a transition from the semiconducting state (0.01 < x) to the metallic state (x > 0.01) occurred within the Te contents 0.01 < x < 0.02 owing to heavy doping. As a result, thermoelectric figure of merit, ZT, of the properly doped CrSb_2-xTe_x compounds (x = 0.005, 0.01, 0.03 and 0.05) was improved at T > ∼180 K. Specifically, at 310 K the ZT value of CrSb_1.97Te_0.03 is ∼27% larger than that of CrSb₂, indicating that thermoelectric properties of CrSb₂ can be improved by an appropriate substitution of Te for Sb

[en] The Sn doped compounds CrSb_2-xSn_x (0 ≤ x ≤ 0.05) were synthesized and the effect of Sn substitution for Sb on electrical resistivity, thermopower and thermal conductivity of CrSb₂ were investigated from 7 K to 310 K. The results indicate that the temperature dependence of electrical resistivity for CrSb₂ did not change obviously after Sn substitution for Sb. However, the magnitude of the resistivity for CrSb_2-xSn_x decreased monotonically with increasing Sn content. Moreover, absolute value of thermopower |S| decreased continuously with increasing Sn content although its temperature behavior was not influenced substantially by Sn doping. The decrease of both the resistivity and |S| could be ascribed to the increase in electron concentration caused indirectly by Sn substitution for Sb. Additionally, experiments showed that low-temperature lattice thermal conductivity (below ∼100 K) of CrSb_2-xSn_x generally decreased with increasing Sn content, which could be explained as an enhancement of phonon scattering by increased number of Sn atoms. The thermoelectric figure of merit, ZT, of doped compounds CrSb_2-xSn_x (x > 0) decreased as compared to that of un-doped CrSb₂ due to substantial decrease in |S| after doping. Present results suggest that thermoelectric properties of CrSb₂ cannot be enhanced by Sn substitution for Sb

[en] Nanocrystalline (Mg_1-xCd_x)₃Sb₂ (x = 0-0.3) and nominally (Mg_0.7Cd_0.25Ag_0.05)₃Sb₂ with a mean grain size of ∼35 nm were prepared by mechanical alloying plus hot-pressing, and their transport and thermoelectric properties were investigated from 310 K down to 20 K. The results indicated that electric resistivity of (Mg_1-xCd_x)₃Sb₂ decreased with increasing Cd content x, which could be ascribed to increase in carrier concentration indirectly caused by lattice distortion after substituted. The much larger decrease in the resistivity of (Mg_0.7Cd_0.25Ag_0.05)₃Sb₂ than that of (Mg_1-xCd_x)₃Sb₂ should originate from substantial increase in hole concentration due to introduction of acceptor impurity Ag. At lower temperature regimes, Mott's T^-1/4 law was observed, which could be attributed to the severe potential disorder caused by lattice distortion upon doping. Seebeck coefficient of all the substituted and co-doped specimens decreased presumably due to increased carrier concentration. Moreover, thermal conductivity of (Mg_1-xCd_x)₃Sb₂ decreased monotonously with increasing x due to phonon scattering of the impurity (Cd) with greater atomic weight. The presence of slight precipitated elementary Sb and Cd phases should be responsible for the observed larger thermal conductivity of (Mg_0.7Cd_0.25Ag_0.05)₃Sb₂ specimen. The values of the ZT for all the doped specimens enhanced. Especially, ZT of (Mg_0.7Cd_0.25Ag_0.05)₃Sb₂ reach 0.01 at 300 K, which is several orders magnitude higher than that un-doped one and those doped slightly with Cd only. Present result indicates that thermoelectric properties of Mg₃Sb₂ system can be effectively improved by the proper substitution of element Cd and co-doped with element Ag.