Modeling the crystallographic structure of Ho(Ni,Co,Mn)O_(3±δ) perovskite-type manganite

Crystallographic and microstructural properties of Ho(Ni,Co,Mn)O3±dperovskite-type multiferroic material are reported.Samples were synthesized with a modified polymeric precursor method.The synchrotron X-ray powder diffraction(SXRPD)technique associated to Rietveld refinement method was used to perform structural characterization.The crystallographic structures,as well as microstructural properties,were studied to determine unit cell parameters and volume,angles and atomic positions,crystallite size and strain.X-ray energies below the absorption edges of the transition metals helped to determine the mean preferred atomic occupancy for the substituent atoms.Furthermore,analyzing the degree of distortion of the polyhedra centered at the transitions metal atoms led to understanding the structural model of the synthesized phase.X-ray photoelectron spectroscopy(XPS)was performed to evaluate the valence states of the elements,and the tolerance factor and oxygen content.The obtained results indicated a small decrease distortion in structure,close to the HoMnO3 basis compound.In addition,the substituent atoms showed the same distribution and,on average,preferentially occupied the center of the unit cell.

Regulation of the order-disorder phase transition in a Cs_(2)NaFeCl_(6) double perovskite towards reversible thermochromic application

Multifunctional lead-free double perovskites demonstrate remarkable potential towards applications in various fields.Herein,an environmentally-friendly,low-cost,high-throughput Cs_(2)NaFeCl_(6) single crystal with exceedingly high thermal stability is designed and grown.It obtains a cubic lattice system in the temperature range of 80-500 K,accompanied by a completely reversible chromatic variation ranging from yellow to black.Importantly,the intriguing thermochromism is proved to own extremely high reproducibility(over 1000 cycles)without a hysteretic effect,originating from its structural flexibility that including(i)the noteworthy distortion/deformation of[NaCl_(6)]5−and[FeCl_(6)]3−octahedra;(ii)order-disorder arrangement transition of[NaCl_(6)]5−and[FeCl6]3−octahedra as the function of temperature.This study paves the way towards a new class of smart windows and camouflage coatings with an unprecedented colour range based on a Cs_(2)NaFeCl_(6) perovskite.

The interplay between the lattice and magnetism in La(Fe_(11.4)Al_(1.6))C_(0.02) studied by powder neutron diffraction

The crystallographic structure and magnetic properties of La（Fell.4Alz.6）C0.02 are studied by magnetic measurernent and powder neutron diffraction with temperature and applied magnetic field. Rietveld refinement shows that La（Fe11.4Al1.6）C0.02 crystallizes into the cubic NaZn13-type with two different Fe sites： FeI （8b） and FeII （96i）, and that A1 atoms preferentially occupy the FeII site. A ferromagnetic state can he induced at a medial temperature of 39 K-139 K by an external magnetic field of 0.7 T, and a large lattice is correspondingly found at 100 K and 0.7 T. In all other conditions, La（Fe11.4Al1.6）C0.02 has no net magnetization in the paramagnetic （T 〉 TN = 182 K） or antifer- romagnetic states, and thus keeps its small lattice. Analysis of the Fe Fe bond length indicates that the ferromagnetic state prefers longer Fe-Fe distances.

Investigation on Strengthening Mechanism of China Low-Activation Ferrite Steel upon Thermo-Mechanical Treatment

The objective of this study was to investigate the influence of strengthening mechanisms on the high-temperature mechanical properties of China low-activation ferrite(CLF-1)steel,which underwent thermodynamic design and thermo-mechanical treatment(TMT).The microstructure characterization in the normalized and tempered condition and the TMT condition was carried out using optical microscopy,X-ray diffractometer,and scanning electron microscopy with electron backscatter diffraction.High-resolution transmission electron microscopy was employed to determine the crystallographic structures of precipitated phases.The results indicated that the addition of Ti led to an increase in the allocation of C in MC phase and an enhancement in the content of MC phase.Compared to CLF-P steel in the normalized and tempered condition,a 1.5-fold increase in dislocation density and an order of magnitude improvement in MX phase density were achieved after TMT.The formation of high-density nano-scale MC phases during TMT played a significant role in precipitation strengthening due to their favorable coherent relationship with the matrix and low interfacial free energy.The excellent high-temperature mechanical properties observed in CLF-P steel after TMT can be attributed to the combined effects of precipitation strengthening,dislocation strengthening,and lath strengthening.

Implications of Nitrogen Doping on Geometrical and Electronic Structure of the Fullerene Dimers

Because of its unsaturated bonds,C_(60) is susceptible to polymerize into dimers.The implications of nitrogen doping on the geometrical and electronic structure of C_(60) dimers have been ambiguous for years.A quarter-century after the discovery of azafullerene dimer(C_(59)N)_(2),we reported its single crystallographic structure in 2019.