Due to the laminated structure,MAX phases and MAX-phase-like compounds possess outstanding dam-age tolerance capability with good thermal/electrical conductivity and other charming functional prop-erties,showing a bri...Due to the laminated structure,MAX phases and MAX-phase-like compounds possess outstanding dam-age tolerance capability with good thermal/electrical conductivity and other charming functional prop-erties,showing a bright future for structural-functional uses.Here,a new MAX-phase-like ternary car-bide V_(8)P_(6)C with layered characteristics was discovered.Contrary to the alternate stacking of hexagonal-arranged M/A/X atom layers in MAX phases,V_(8)P_(6)C has a layered structure formed by a repeated stacking of the slabs consisting of V_(6)C-octahedrons and VP 6-distorted-octahedrons in three-atomic layers thick.The thermal expansion anisotropy was revealed,with the thermal expansion coefficients(TECs)along a-axis,c-axis,and the average value,equal toα_(a)=8.55(5)μK^(−1),α_(c)=10.23(5)μK^(−1),andα_(L)=9.14(5)μK^(−1),respectively.The dilation along the c-axis was mainly dominated by out-plane V-P bonds be-tween layered slabs.According to the pressure-dependent lattice parameters,the polycrystalline bulk modulus(B_(0)=185(9)GPa)and high compressibility anisotropy factor(B_(a)/B_(c)=1.64)was found.Mean-while,the second-order elastic constants were calculated,and the elastic moduli,E=303 GPa,B=198 GPa,G=122 GPa,andν=0.246,were obtained.And the weak connection between layer slabs by out-plane V1-P bond was revealed by the bond stiffness model,with a bond stiffness close to the M-A bond in MAX phases.Furthermore,good damage tolerance capability was predicted according to Paugh’s ratio(G/B=0.616)and Cauchy pressure(P_(a)=0 GPa,P_(c)=-7.5 GPa),even better than those of typical MAX phases.The discovery of V_(8)P_(6)C provides a new member of MAX-phase-like damage-tolerant ceramic with relatively low density,moderate thermal expansion,and anisotropic compressibility,and the unique lay-ered structure is inspiring for exploring new layered ternary ceramics.展开更多
基金supported by the National Science Foundation for Young Scientists of China(No.51902055)the Natural Science Foundation of Fujian Province(No.2021J011077)+1 种基金the Top Young Talents of Eagle Program of Fujian Province(No.KY310255)State Key Laboratory of Structural Chemistry(No.20230020).
文摘Due to the laminated structure,MAX phases and MAX-phase-like compounds possess outstanding dam-age tolerance capability with good thermal/electrical conductivity and other charming functional prop-erties,showing a bright future for structural-functional uses.Here,a new MAX-phase-like ternary car-bide V_(8)P_(6)C with layered characteristics was discovered.Contrary to the alternate stacking of hexagonal-arranged M/A/X atom layers in MAX phases,V_(8)P_(6)C has a layered structure formed by a repeated stacking of the slabs consisting of V_(6)C-octahedrons and VP 6-distorted-octahedrons in three-atomic layers thick.The thermal expansion anisotropy was revealed,with the thermal expansion coefficients(TECs)along a-axis,c-axis,and the average value,equal toα_(a)=8.55(5)μK^(−1),α_(c)=10.23(5)μK^(−1),andα_(L)=9.14(5)μK^(−1),respectively.The dilation along the c-axis was mainly dominated by out-plane V-P bonds be-tween layered slabs.According to the pressure-dependent lattice parameters,the polycrystalline bulk modulus(B_(0)=185(9)GPa)and high compressibility anisotropy factor(B_(a)/B_(c)=1.64)was found.Mean-while,the second-order elastic constants were calculated,and the elastic moduli,E=303 GPa,B=198 GPa,G=122 GPa,andν=0.246,were obtained.And the weak connection between layer slabs by out-plane V1-P bond was revealed by the bond stiffness model,with a bond stiffness close to the M-A bond in MAX phases.Furthermore,good damage tolerance capability was predicted according to Paugh’s ratio(G/B=0.616)and Cauchy pressure(P_(a)=0 GPa,P_(c)=-7.5 GPa),even better than those of typical MAX phases.The discovery of V_(8)P_(6)C provides a new member of MAX-phase-like damage-tolerant ceramic with relatively low density,moderate thermal expansion,and anisotropic compressibility,and the unique lay-ered structure is inspiring for exploring new layered ternary ceramics.
