Guided by the theoretical prediction,a new MAX phase V2SnC was synthesized experimentally for the first time by reaction of V,Sn,and C mixtures at 1000°C.The chemical composition and crystal structure of this new...Guided by the theoretical prediction,a new MAX phase V2SnC was synthesized experimentally for the first time by reaction of V,Sn,and C mixtures at 1000°C.The chemical composition and crystal structure of this new compound were identified by the cross-check combination of first-principles calculations,X-ray diffraction(XRD),energy dispersive X-ray spectroscopy(EDS),and high resolution scanning transmission electron microscopy(HR-STEM).The stacking sequence of V2C and Sn layers results in a crystal structure of space group P63/mmc.The a-and c-lattice parameters,which were determined by the Rietveld analysis of powder XRD pattern,are 0.2981(0)nm and 1.3470(6)nm,respectively.The atomic positions are V at 4f(1/3,2/3,0.0776(5)),Sn at 2d(2/3,1/3,1/4),and C at 2a(0,0,0).A new set of XRD data of V2SnC was also obtained.Theoretical calculations suggest that this new compound is stable with negative formation energy and formation enthalpy,satisfied Born-Huang criteria of mechanical stability,and positive phonon branches over the Brillouin zone.It also has low shear deformation resistance c44(second-order elastic constant,cij)and shear modulus(G),positive Cauchy pressure,and low Pugh’s ratio(G/B=0.500<0.571),which is regarded as a quasi-ductile MAX phase.The mechanism underpinning the quasi-ductility is associated with the presence of a metallic bond.展开更多
This study reported the synthesis of magnetic solid solutions V2(A_(x)B_(y)Sn_(1-x-y))C(where A and B are Mn,Fe,or Co)MAX phases.These materials were prepared by incorporating magnetic elements into the V_(2)SnC MAX p...This study reported the synthesis of magnetic solid solutions V2(A_(x)B_(y)Sn_(1-x-y))C(where A and B are Mn,Fe,or Co)MAX phases.These materials were prepared by incorporating magnetic elements into the V_(2)SnC MAX phase via pressure-less sintering at 1000℃for 3 hours.XRD analysis reveals that the composition with x=y=0.2 exhibits a shift of diffraction peaks to higher angles,indicating lattice parameter changes,and achieves the highest phase purity with the maximum solid solution limit,further increases in the dopant content led to the formation of impurities.While the solid solution of magnetic elements preserves the characteristic layered structure of the MAX phase,it successfully induces magnetic properties.The magnetic transition temperatures for these solid solutions ranges from 61 to 200 K.Specifically,V_(2)(Mn_(x)Co_(y)Sn_(1-x-y))C demonstrated hard magnetic characteristics,with a high saturation magnetization(6.536 emu/g)and large remanence(4.236 emu/g).In contrast,V_(2)(Mn_(x)Fe_(y)Sn_(1-x-y))C and V2(Fe_(x)Co_(y)Sn_(1-x-y))C exhibits soft magnetic behavior,evidenced by their narrow hysteresis loops and low coercivity.Their saturation magnetization values are 3.80 and 1.784 emu/g,respectively.The distinctly"S"-shaped hysteresis loop of V_(2)(Fe_(x)Co_(y)Sn_(1-x-y))C further confirms its soft magnetic nature.展开更多
基金This study is supported by Thousand Talents Program of Sichuan Province,the Open Project of State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials(17kffk01)Outstanding Young Scientific and Technical Talents in Sichuan Province(2019JDJQ0009)and the National Natural Science Foundation of China(No.51741208).
文摘Guided by the theoretical prediction,a new MAX phase V2SnC was synthesized experimentally for the first time by reaction of V,Sn,and C mixtures at 1000°C.The chemical composition and crystal structure of this new compound were identified by the cross-check combination of first-principles calculations,X-ray diffraction(XRD),energy dispersive X-ray spectroscopy(EDS),and high resolution scanning transmission electron microscopy(HR-STEM).The stacking sequence of V2C and Sn layers results in a crystal structure of space group P63/mmc.The a-and c-lattice parameters,which were determined by the Rietveld analysis of powder XRD pattern,are 0.2981(0)nm and 1.3470(6)nm,respectively.The atomic positions are V at 4f(1/3,2/3,0.0776(5)),Sn at 2d(2/3,1/3,1/4),and C at 2a(0,0,0).A new set of XRD data of V2SnC was also obtained.Theoretical calculations suggest that this new compound is stable with negative formation energy and formation enthalpy,satisfied Born-Huang criteria of mechanical stability,and positive phonon branches over the Brillouin zone.It also has low shear deformation resistance c44(second-order elastic constant,cij)and shear modulus(G),positive Cauchy pressure,and low Pugh’s ratio(G/B=0.500<0.571),which is regarded as a quasi-ductile MAX phase.The mechanism underpinning the quasi-ductility is associated with the presence of a metallic bond.
基金Funded by the National Natural Science Foundation for Young Scholars of China(No.51302073)the Hubei Provincial Key Laboratory of Green Materials for Light Industry,Hubei University of Technology(No.202509B13)。
文摘This study reported the synthesis of magnetic solid solutions V2(A_(x)B_(y)Sn_(1-x-y))C(where A and B are Mn,Fe,or Co)MAX phases.These materials were prepared by incorporating magnetic elements into the V_(2)SnC MAX phase via pressure-less sintering at 1000℃for 3 hours.XRD analysis reveals that the composition with x=y=0.2 exhibits a shift of diffraction peaks to higher angles,indicating lattice parameter changes,and achieves the highest phase purity with the maximum solid solution limit,further increases in the dopant content led to the formation of impurities.While the solid solution of magnetic elements preserves the characteristic layered structure of the MAX phase,it successfully induces magnetic properties.The magnetic transition temperatures for these solid solutions ranges from 61 to 200 K.Specifically,V_(2)(Mn_(x)Co_(y)Sn_(1-x-y))C demonstrated hard magnetic characteristics,with a high saturation magnetization(6.536 emu/g)and large remanence(4.236 emu/g).In contrast,V_(2)(Mn_(x)Fe_(y)Sn_(1-x-y))C and V2(Fe_(x)Co_(y)Sn_(1-x-y))C exhibits soft magnetic behavior,evidenced by their narrow hysteresis loops and low coercivity.Their saturation magnetization values are 3.80 and 1.784 emu/g,respectively.The distinctly"S"-shaped hysteresis loop of V_(2)(Fe_(x)Co_(y)Sn_(1-x-y))C further confirms its soft magnetic nature.
