[en] Perovskite La_0.5Ca_0.5MnO₃ (LCM) based materials are promising for electrode construction but their poor conductivities often lead to limited electrochemical performances. In this work, LCM was combined with Ag through the two-step process based on sol-gel and silver mirror reaction. The as-obtained LCM@Ag composites were characterized by scanning electron microscopy and x-ray powder diffraction. The mass percent determined by energy disperse spectroscopy combined with x-ray photoelectron spectroscopy was estimated at 5%. The electrochemical measurements showed LCM@Ag to possess superior specific capacitance of 287 C g⁻¹ (179 F g⁻¹) at 1.5 A g⁻¹ while pure LCM delivered only 187 C g⁻¹ (117 F g⁻¹). The key to the improvement of performance can be attributed to the silver nanoparticle introduction, which leads to the enhancement of the electron transport capacity and ion diffusion for the composite. Meanwhile, the cycle stability slightly improved and the retention rate after 3,000 cycles at 10 A g⁻¹ reached 66%. In sum, La_0.5Ca_0.5MnO₃ perovskite system looks promising for electrode construction, where silver modification could improve the overall electrochemical properties. (paper)

[en] Experimental results of a direct current enhanced inductively coupled plasma (DCE-ICP) source which consists of a typical cylindrical ICP source and a plate-to-grid DC electrode are reported. With the use of this new source, the plasma characteristic parameters, namely, electron density, electron temperature and plasma uniformity, are measured by Langmuir floating double probe. It is found that DC discharge enhances the electron density and decreases the electron temperature, dramatically. Moreover, the plasma uniformity is obviously improved with the operation of DC and radio frequency (RF) hybrid discharge. Furthermore, the nonlinear enhancement effect of electron density with DC + RF hybrid discharge is confirmed. The presented observation indicates that the DCE-ICP source provides an effective method to obtain high-density uniform plasma, which is desirable for practical industrial applications. (paper)

[en] Stable operations of single direct current (DC) discharge, single radio frequency (RF) discharge and DC + RF hybrid discharge are achieved in a specially-designed DC enhanced inductively-coupled plasma (DCE-ICP) source. Their plasma characteristics, such as electron density, electron temperature and the electron density spatial distribution profiles are investigated and compared experimentally at different gas pressures. It is found that under the condition of single RF discharge, the electron density distribution profiles show a ‘convex’ shape and ‘saddle’ shape at gas pressures of 3 mTorr and 150 mTorr respectively. This result can be attributed to the transition of electron kinetics from nonlocal to local kinetics with an increase in gas pressure. Moreover, in the operation of DC + RF hybrid discharge at different gas pressures, the DC discharge has different effects on plasma uniformity. The plasma uniformity can be improved by modulating DC power at a high pressure of 150 mTorr where local electron kinetics is dominant, whereas plasma uniformity deteriorates at a low pressure of 3 mTorr where nonlocal electron kinetics prevails. This phenomenon, as analyzed, is due to the obvious nonlinear enhancement effect of electron density at the chamber center, and the inherent radial distribution difference in the electron density with single RF discharge at different gas pressures. (paper)

[en] The effects of driving frequency on plasma parameters and electron heating efficiency are studied in cylindrical inductively coupled plasma (ICP) source. Measurements are made in an Ar discharge for driving frequency at 13.56/2 MHz, and pressures of 0.4–1.2 Pa. In 13.56 MHz discharge, higher electron density (n _e) and higher electron temperature (T _e) are observed in comparison with 2 MHz discharge at 0.6–1.2 Pa. However, slightly higher n _e and T _e are observed in 2 MHz discharge at 0.4 Pa. This observation is explained by enhanced electron heating efficiency due to the resonance between the oscillation of 2 MHz electromagnetic field and electron-neutral collision process at 0.4 Pa. It is also found that the variation of T _e distribution is different in 13.56 and 2 MHz discharge. For ICP at 13.56 MHz, T _e shows an edge-high profile at 0.4–1.2 Pa. For 2 MHz discharge, T _e remains an edge-high distribution at 0.4–0.8 Pa. However, the distribution pattern involves into a center-high profile at 0.9–1.2 Pa. The spatial profiles of n _e remain a center-high shape in both 13.56 and 2 MHz discharges, which indicates the nonlocal kinetics at low pressures. Better uniformity could be achieved by using 2 MHz discharge. The effects of gas pressure on plasma parameters are also examined. An increase in gas pressure necessitates the rise of n _e in both 13.56 and 2 MHz discharges. Meanwhile, T _e drops when gas pressure increases and shows a flatter distribution at higher pressure. (paper)

[en] The phenomenon of T-linear resistivity commonly observed in a number of strange metals has been widely seen as evidence for the breakdown of the quasiparticle picture of metals. This study shows that a recently discovered H/T scaling relationship in the magnetoresistance of the strange metal BaFe₂(As_1-xP_x)₂ is independent of the relative orientations of current and magnetic field. Rather, its magnitude and form depend only on the orientation of the magnetic field with respect to a single crystallographic axis: the direction perpendicular to the magnetic iron layers. In this work, this finding suggests that the magnetotransport scaling does not originate from the conventional averaging or orbital velocity of quasiparticles as they traverse a Fermi surface, but rather from dissipation arising from two-dimensional correlations.