磁制冷是一种利用材料的磁热效应进行制冷的新型制冷技术,相比于传统气体压缩制冷,因其绿色环保、高效节能等优点而备受关注。在众多磁相变合金材料中,人们对Mn_2Sb基亚铁磁相变合金研究甚少。文章研究了Cr取代Mn后亚铁磁性Mn_(2-x)Cr_xSb_(0.95)In_(0.05)(x=0.05,0.09,0.13)合金的磁性和磁热性能。室温XRD数据表明合金在室温附近以四角Cu_2Sb型结构为主相。由于反铁磁中有高磁响应,因此从XRD图谱中能观察到少量的铁磁MnSb杂相。随着温度的降低,在这些合金中,发生了亚铁磁到反铁磁的一级磁致弹性转变。同时,在亚铁磁区域观察到两个自旋重新取向转变。由于反铁磁-亚铁磁的转变过程中磁化强度突变,使得在Mn_(1.91)Cr_(0.09)Sb_(0.95)In_(0.05)合金中在0~10 k Oe的磁场变化中获得高达1.63 J/kg·K的大磁熵变。目前的研究可能有助于研究和开发新的磁性冷材料。 相似文献
We present an extensive study of the electronic properties and carrier transport in phosphorene nanoribbons (PNRs) with edge defects by using rigorous atomistic quantum transport simulations. This study reports on the size- and defect-dependent scaling laws governing the transport gap, and the mean free path and carrier mobility in the PNRs of interest for future nanoelectronics applications. Our results indicate that PNRs with armchair edges (aPNRs) are more immune to defects than zig-zag PNRs (zPNRs), while both PNR types exhibit superior immunity to defects relative to graphene nanoribbons (GNRs). An investigation of the mean free path demonstrated that even in the case of a low defect density the transport in PNRs is diffusive, and the carrier mobility remains a meaningful transport parameter even in ultra-small PNRs. We found that the electron–hole mobility asymmetry (present in large-area phosphorene) is retained only in zPNRs for W > 4 nm, while in other cases the asymmetry is smoothed out by edge defect scattering. Furthermore, we showed that aPNRs outperform both zPNRs and GNRs in terms of carrier mobility, and that PNRs generally offer a superior mobility-bandgap trade-off, relative to GNRs and monolayer MoS2. This work identifies PNRs as a promising material for the extremely scaled transistor channels in future post-silicon electronic technology, and presents a persuasive argument for experimental work on nanostructured phosphorene.
Pulsed laser deposition technique was used to grow off c-axis oriented SrBi2(Ta0.95V0.05)2O9 (SBTV) ferroelectric thin films. X-ray diffraction studies revealed the c-axis suppression in the films grown at lower substrate temperature (350°C) followed by annealing at higher temperatures (650°C). In-plane lattice parameters of the films were decreased with increase in annealing temperature. SBTV films annealed at 750°C exhibited enhanced ferroelectric properties with remanent polarization (2Pr) of 31.5 C/cm2 and coercive field (Ec) of 157 kV/cm. The dielectric permmitivity of the films increased with increase in annealing temperature and it was attributed to the grain size dependence. The films annealed at 750°C showed maximum value of dielectric permittivity 172 with a tangential loss of 0.1, at 100 kHz. Higher value of dissipation factor at lower annealing temperature is explained in terms of space charge accumulation at grain boundaries. The leakage current densities of the films follow ohmic behavior at low field regime and space charge limited current dominates at higher fields. 相似文献
Sr(Ti0.95Zr0.05)O3 ceramic was sintered using x mol.% CTS (x = 0, 0.5, 1.5, 4, 7) as sintering additive for the first time. Although Sr(Ti0.95Zr0.05)O3 ceramic could not be fully sintered even at 1420 °C, the densification temperature could be decreased to 1280 °C by using CTS, which begin melting when temperature reaches higher than 1150 °C. The microstructures of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Apparent density and the dielectric properties were established at room temperature. The measuring frequency was 1 MHz. The microstructure and dielectric properties greatly changed depending on the amount of CTS additive. The optimum concentration to obtain nicer dielectric properties was 0.5 mol.%. 相似文献
