Observation of low thermal expansion behavior and weak thermal anisotropy in M_(3)A_(2)C phases  

作　　者：Hongxiang Chen Zhilong Zhang Jun Deng Zhijie Lin Chunfu Hong Shixuan Du Pinqiang Dai 

机构地区：[1]School of Materials Science and Engineering, Fujian University of Technology, Fuzhou 350118, China [2]Institute of Physics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100190, China [3]Fujian Provincial Key Laboratory of Advanced Materials Processing and Application, Fuzhou 350118, China [4]Center for Advanced Energy and Functional Materials, Fujian University of Technology, Fuzhou 350118, China [5]Songshan Lake Materials Laboratory, Dongguan 523808, China [6]CAS Key Laboratory of Vacuum Physics, Beijing 100049, China

出　　处：《Journal of Materials Science & Technology》2023年第23期210-216,共7页材料科学技术（英文版）

基　　金：financially supported by the National Science Foundation for Young Scientists of China(No.51902055);the Natural Science Foundation of Fujian Province(No.2021J011077);the Fuzhou Science and Technology Plan Project(No.2021-P-049).

摘　　要：M_(3)A_(2)X phases,named 321 phases,are an atypical series of MAX phases featuring in the MA-triangular-prism bilayers,with the A=As/P,exhibiting excellent elastic properties.This work systematically studies the thermal expansion properties of 321 phases.We found their average linear thermal expansion coefficients(TECs),α_(L)=5-6μK^(–1),are the lowest among the reported values of MAX phases.The lowest average TEC was found in Nb_(3)As_(2)C(αa=4.46(4)μK^(–1),αc=5.09(4)μK–1,αL=5.09(4)μK–1).The average TEC and anisotropy factor(αc/αa)of Nb_(3)As_(2)C and Nb_(3)P_(2)C were lower than the ones of the corresponding 211 phases.The best isotropy performance was found in Nb_(3)P_(2)C (αc/αa=1.11).Moreover,our first-principles calculations demonstrate that the weaker chemical bonding between Nb-As/P than Nb-C induces thermal expansion in M_(3)A_(2)X phases.Furthermore,a relatively weaker anharmonic effect in 321 phases than in the 211 phases was revealed by the as-calculated average Grüneisen parameters,which account for the lower TECs in 321 phases.The low TECs and enhanced thermal isotropy make 321 phases outstanding among MAX phases,which could be sound candidates for varying-temperature structural-functional components.

关 键 词：Max phase Layered ceramics Thermal expansion ANISOTROPY X-ray diffraction 

分 类 号：TQ174.75[化学工程—陶瓷工业]