[en] Powder samples Sr₃Y_1−x−y(PO₄)₃:xTm³⁺-yDy³⁺ were synthesized by the conventional solid-state reaction method. By appropriate tuning of activator content, the emission color can be adjusted around blue to white and yellow. It was discovered that the energy transfer from Tm³⁺ to Dy³⁺ was demonstrated to be via the intensity of Dy³⁺ emission increase with the increase of Tm³⁺ concentration. By changing the doping concentration of Tm³⁺ and Dy³⁺ in Sr₃Y(PO₄)₃, white-emitting phosphors are produced by 350 nm excitation wavelength, their corresponding color coordinates are very close to the white color chromaticity coordinates (x=0.33, y=0.33). Finally, Sr₃Y_1−x−y(PO₄)₃:xTm³⁺−yDy³⁺ phosphors could be a good promising single-component white light-emitting UV-convertible phosphor in the field of white LEDs. -- Highlights: • The Sr₃Y_1−x−y(PO₄)₃:xTm³⁺−yDy³⁺ phosphors were synthesized by the conventional solid-state reaction method. • The energy transfer in between Tm³⁺ and Dy³⁺ was observed and explained. • The phosphors can be efficiently excited by a UV light. • The Sr₃Y_1−x−y(PO₄)₃:xTm³⁺-yDy³⁺ phosphor could be a better candidate white phosphor for UV W-LEDs

[en] The cryostat for FEB (fusion engineering breeder) is described. The estimated results of thermal loads are given

[en] BaZr_xTi_1−xO₃ (x = 0.2, 0.25, 0.3) ceramics were prepared by a citrate method. The ferroelectric phase transition behavior and bias electric-field-induced dielectric nonlinearity of the ceramics were investigated. With increasing zirconium content, the phase transition behavior of the ceramics changed from a diffusion phase transition to relaxor-like behavior. Applying bias electric field in diverse manners led to differing effects on the dielectric nonlinearity, depending on the zirconium content of the ceramics. These dielectric phenomena were related to the polarization response of polar nano-regions (PNRs) embedded in the ceramics, which are macroscopically in the paraelectric state at room temperature. The characteristic parameters of PNRs were determined by fitting the dielectric constants under bias electric field to a multipolarization mechanism model. It was found that the size of PNRs was decreased with increasing zirconium content. The evolution of the phase transition behavior and dielectric nonlinearity with zirconium content was interpreted in relation to the size change of PNRs

[en] The structure and energy storage properties of Ba_0.95Ca_0.05Zr_0.3Ti_0.7O₃ ceramics with different contents of MgO–CaO–Al₂O₃–SiO₂ glass additive added were examined. The dielectric properties of the specimens were studied as a function of temperature and frequency. The specimens displayed a relaxor-like behavior and the glass addition enhanced the diffuseness degree of the ferroelectric–paraelectric phase transition. With increasing glass additive content, the dielectric loss of the specimens steadily increased. Over several decades of frequency, the ac conductivity data of the specimens agreed with the power-law relation of the universal dielectric response (UDR) model, indicating the presence of hopping motion of polarization carriers. Complex impedance analysis confirmed that oxygen ions are the mobile carriers in the specimens. The origin of oxygen-ion conduction in the glass-added specimens is explained in relation to a chemical reaction between the perovskite grains and the glass additive. It is confirmed that, for the glass-added specimens, polarization response resulting from oxygen-ion hopping is responsible for an overall increase of their dielectric loss in a wide frequency range.

[en] The Bohm criterion of the sheath in the multicomponent electronegative collisional plasma is developed with a two-fluid model. It is discussed that different charge particles affect the Bohm criterion for the sheath of a one-dimensional stationary plasma. Numerical calculation results are obtained through quasi-Newton method. It is shown that the upper and lower limits for the sheath criterion exist. And the ion Mach number increases with the increase of secondary electron emission coefficient, it decreases with the increase of negative ions. In addition, the upper and lower limits for the sheath criterion depend on the temperature of ions, the ion-neutral collision and the charge of the ions. (authors)

[en] In this work, a simple and efficient procedure for the mutual separation of trivalent americium and curium (Am(III) and Cm(III)) has been provided by extraction chromatography with the novel developed XAD-7-based BCPDTPA composite sorbent in nitric acid solution. The batch experiments and column separation studies were systematically performed. The influences of nitric acid concentration and temperature on the weight distribution coefficients and separation factors for Am(III) and Cm(III) were determined in the batch experiments. Based on the data in the batch studies, the column experiments were designed and conducted. A satisfactory separation of Am(III) and Cm(III) was accomplished in a 1.4 mL column (φ5 × 70 mm) with 0.10 mol L^-1 nitric acid solution. It is noted that the partitioning process can work with single nitric acid solution without any additives. (author)

[en] In this paper, a two-dimensional physical model is established according to the discharging process in the Hall thruster discharge channel using the particle-in-cell method. The influences of discharge voltage on the distributions of potential, ion radial flow, and discharge current are investigated in a fixed magnetic field configuration. It is found that, with the increase of discharge voltage, especially during 250-650 V, the ion radial flow and the collision frequency between ions and the wall are decreased, but the discharge current is increased. The electron temperature saturation is observed between 400-450 V and the maximal value decreases during this region. When the discharge voltage reaches 700 V, the potential distribution in the axis direction expands to the anode significantly, the ionization region becomes close to the anode, and the acceleration region grows longer. Besides, ion radial flow and the collision frequency between ions and the wall are also increased when the discharge voltage exceeds 650 V. (paper)

[en] The influences of the low-emissive graphite segmented electrode placed near the channel exit on the discharge characteristics of a Hall thruster are studied using the particle-in-cell method. A two-dimensional physical model is established according to the Hall thruster discharge channel configuration. The effects of electrode length on the potential, ion density, electron temperature, ionization rate and discharge current are investigated. It is found that, with the increasing of the segmented electrode length, the equipotential lines bend towards the channel exit, and approximately parallel to the wall at the channel surface, the radial velocity and radial flow of ions are increased, and the electron temperature is also enhanced. Due to the conductive characteristic of electrodes, the radial electric field and the axial electron conductivity near the wall are enhanced, and the probability of the electron-atom ionization is reduced, which leads to the degradation of the ionization rate in the discharge channel. However, the interaction between electrons and the wall enhances the near wall conductivity, therefore the discharge current grows along with the segmented electrode length, and the performance of the thruster is also affected. (paper)

[en] There exists strong interaction between the plasma and channel wall in the Hall thruster, which greatly affects the discharge performance of the thruster. In this paper, a two-dimensional physical model is established based on the actual size of an Aton P70 Hall thruster discharge channel. The particle-in-cell simulation method is applied to study the influences of segmented low emissive graphite electrode biased with anode voltage on the discharge characteristics of the Hall thruster channel. The influences of segmented electrode placed at the ionization region on electric potential, ion number density, electron temperature, ionization rate, discharge current and specific impulse are discussed. The results show that, when segmented electrode is placed at the ionization region, the axial length of the acceleration region is shortened, the equipotential lines tend to be vertical with wall at the acceleration region, thus radial velocity of ions is reduced along with the wall corrosion. The axial position of the maximal electron temperature moves towards the exit with the expansion of ionization region. Furthermore, the electron-wall collision frequency and ionization rate also increase, the discharge current decreases and the specific impulse of the Hall thruster is slightly enhanced. (paper)

[en] In plasma source ion implantations, a target immersed directly in a uniform plasma is biased with a high negative voltage pulse. Then an expanding plasma sheath forms between the plasma and the solid target surface, and implants ions into the material. In this paper, the evolution of collisionless and collisional sheaths in different geometries, and for various gas pressures, has been numerically studied using a one-dimensional fluid model. Collisions are included in the model through a collisional drag term in the equation of ion motion. Besides the sheath evolution, plots for the average kinetic energy as well as the current density of ion implantations at the target surface are presented. For the collisional sheath, it is found that the final sheath thickness in planar and spherical (or cylindrical) geometries differs from each other significantly. Also, computational results of the collisional sheath in different geometries are in good agreement with those obtained by analytic models