Preparation And Properties Of Magnetic Ternary Ceramic (Cr_2-xMn_x)GaC

Cr₂GaC is one of the MAX phases of the ternary layered materials,which represent a class of ternary transition metal carbides or nitrides,with a common formula M_n+1AX_n（n=1,2,3）,where M is an early transition metal,A represents a part of the third or fourth main group,and X is C or N.MAX ceramics combines the advantages of ceramic and metallic materials due to its special crystal structure and the type of chemical bonds.MAX phase solid solution(Cr_2-xMn_x)GaC with magnetic properties can be obtained by doping with Mn atoms,which is an ideal material for magnetism fields such as data storage,magnetic recording and spintronics.In this paper,MAX phase Cr₂GaC and solid solution(Cr_2-xMn_x)GaC were prepared by pressureless sintering,the effects of Mn doped Cr₂GaC to its physical properties were investigated.MAX phase Cr₂GaC was synthesized by pressureless sintering with reagents of Cr,C and Ga,the results show that the purity of Cr₂GaC may increase gradually with the increase of reaction temperature and holding time,after holding at 1050°C for 2 h,almost pure MAX phase Cr₂GaC can be obtained,the lattice parameters of the sintered Cr₂GaC are a=b=2.560?,c=12.126?.And on this basis the MAX phase solid solutions(Cr_2-xMn_x)GaC were prepared through the reagents of Cr,Mn,C and Ga.Compared with Cr₂GaC,the reaction times to synthesis(Cr_2-xMn_x)GaC are much longer,and the reaction can be completely carried out after holding for 24 h at 1050°C.The amounts of Mn doped is related to the values of x,when the Mn contents of x≤0.4,the amounts of Mn doped will add gradually with the increase of x and reach the maximum at x=0.4,where the offset of XRD is most obvious,and then decrease with the increase of x after x>0.4.The micro-morphology and crystal structure of Cr₂GaC haven’t changed significantly after the doping of Mn,except to its slight decrease in lattice parameter and interplanar spacing.By characterizing the magnetic properties of(Cr_2-xMn_x)GaC samples,it was confirmed that the doping of Mn succeeded in imparting magnetic to Cr₂GaC.The doped(Cr_2-xMn_x)GaC possess the low-temperature magnetic properties,which Curie temperature are around 100 K.Taking the sample of x=0.4 as an example,under the condition of 10 K,the coercive force of Cr_1.6Mn_0.4GaC is 35 Oe,and the residual magnetic flux density is 0.1 emu/g,which has the characteristics of low-temperature soft magnetic materials.The(Cr_2-xMn_x)GaC samples prepared posses well electrical cycle characteristics,the mass ratio capacitance of(Cr_2-xMn_x)GaC electrodes where x=0,0.2,0.4 and 0.6 are 11.33 F/g,11.07 F/g,10.46 F/g and 9.41 F/g,respectively.The doping of Mn may reduce the capacitance characteristics of Cr₂GaC,but increase its electrical conductivity values.