Photoluminescence from Electron-Beam Deposited CeO2 Thin Film after High Temperature Thermal Annealing

CeOx films are deposited onto the surface of a SiO2 matrix embedded with Si nanocrystals （nc-Si/SiO2） by electron-beam evaporation of CeO2 powder in high vacuum. By tuning the thickness of the CeOx film, photoluminescence （PL） spectra centred at 330, 358, 378, 388, 400, and 450hm, respectively, are observed. It has been identified that the PL centred at 358, 388 and 400 nm are from cerium silicide compounds, and those centred at 330hm, 378nm are due to Ce^3＋ ions, while the 450hm PL is from the defects in the SiO2 matrix.

Exchange Coupling and Stability of SmCo7-xHfx

Electronic structure of SmCo7-xHfx compound is calculated by using the multi-scattering Xα method. It is shown that a few of electrons can transfer to the Sm 5d orbital due to orbital hybridization between Sm and Co atoms. The 3d-5d coupling is stronger, which is the main reason to result in the long-range ferromagnetic order between Sm and Co atoms in SmCo7-xHfx. According to the Stoner criterion, the result of spin-unpolarized calculation for the Sm5Co32Hf2 duster could lead to a better understanding of why the ferromagnetic SmCo7-xHfx is a stable phase. For the Sm5Co32Hf2 duster the Fermi level is situated at the overall maximum of the density of states. Moreover the duster wavefunctions at EF are antibonding and hence highly localized in real space, which would lead to a large value for the duster Stoner integral. Thus a rationalization for the magnetic stability of SmCo7-xHfx has been obtained.

Synthesis and Spectroscopic Study of a New Li-B-V-O Cluster Compound

In this paper,the synthesis of a novel polyoxovanadiumborate[Li(H2O)3]3[V12B18O48(OH)12(OH)]·(H2O)5by hydrothermal method.FTIR,2DFTIR and UV-Vis absorption spectroscopy were employed to explore the relationships between structure and properties of 3-D compound 1.

Electron-irradiation-facilitated production of chemically homogenized nanotwins in nanolaminated carbides

Twin boundaries have been exploited to stabilize ultrafine grains and improve mechanical properties of nanomaterials.The production of the twin boundaries and nanotwins is however prohibitively challenging in carbide ceramics.Using a scanning transmission electron microscope as a unique platform for atomic-scale structure engineering,we demonstrate that twin platelets could be produced in carbides by engineering antisite defects.The antisite defects at metal sites in various layered ternary carbides are collectively and controllably generated,and the metal elements are homogenized by electron irradiation,which transforms a twin-like lamellae into nanotwin platelets.Accompanying chemical homogenization,α-Ti_(3)AlC_(2) transforms to unconventionalβ-Ti_(3)AiC_(2).The chemical homogeneity and the width of the twin platelets can be tuned by dose and energy of bombarding electrons.Chemically homogenized nanotwins can boost hardness by~45%.Our results provide a new way to produce ultrathin(<5 nm)nanotwin platelets in scientifically and technologically important carbide materials and showcase feasibility of defect engineering by an angstrom-sized electron probe.

Disordered Fragments of Chemical Structures Based on Single-crystal X-ray Diffraction

For the reported chemical structures,the disordered fragments of the structure acting as hosts and guests are common and unmanageable for crystallographers.How to analyze and treat such disordered assemblies is an important task for crystallographers.It is often difficult for some researchers to refine the disordered structures,even to mechanically justify the refined consequence in the absence of expertise.Herein,some examples of disorder refinements selected from the literature,including the disordered assemblies of nitrate,perchlorate,alkyl,aromatic assemblies,and guest solvent molecules,are summarized and discussed to provide practical advice for investigating the disorders for crystallographic researchers and beginners.The refinement approach for these disordered assemblies is also discussed in detail,which is helpful for crystallographers.