硫族MAX相硼化物的物相稳定性和性能预测  

Predictions of Phase Stability and Properties of S-group Elements Containing MAX Borides

作　　者：张宇晨[1] 陆知遥 赫晓东[1] 宋广平[1] 朱春城[2] 郑永挺[1] 柏跃磊[1] ZHANG Yuchen;LU Zhiyao;HE Xiaodong;SONG Guangping;ZHU Chuncheng;ZHENG Yongting;BAI Yuelei(National Key Laboratory of Science and Technology on Advanced Composites in Special Environments/Center for Composite Materials and Structures,Harbin Institute of Technology,Harbin 150080,China;School of Chemistry and Chemical Engineering,Harbin Normal University,Harbin 150025,China)

机构地区：[1]哈尔滨工业大学特种环境复合材料技术国家级重点实验室/复合材料与结构研究所,哈尔滨150080 [2]哈尔滨师范大学化学与化工学院,哈尔滨150025

出　　处：《无机材料学报》2024年第2期225-232,I0001-I0003,共11页Journal of Inorganic Materials

基　　金：国家自然科学基金面上项目(51972080);特种环境复合材料技术国家级重点实验室基金(JCKYS2022603C028)。

摘　　要：Zr2SB、Hf2SB、Zr2SeB、Hf2SeB、Hf2TeB都是近期发现的硫族MAX相硼化物,与典型MAX相相比,具有明显不同的性质,因此备受人们关注。本文采用第一性原理并结合“线性优化法”、键刚度模型和准简谐近似研究了MAX相硼化物(M=Zr,Hf;A=S,Se,Te)的物相稳定性、力学性能和热性能。理论分析结果与目前可用的实验结果一致。经热力学和本征稳定性分析后发现,只有M2AB可以稳定存在。较短的M−A键与M−B键长使Hf系化合物的键刚度高于Zr系化合物,这也同样导致Hf系化合物的硬度高于Zr系。随着A元素由S到Se再到Te,M−B与M−A键长逐渐增加,键刚度减小导致弹性模量降低。而且,这些化合物的体积模量取决于其平均化学键刚度。更加重要的是,最弱键和最强键的刚度比(kmin/kmax)较高,显示这些MAX相硼化物不同于传统MAX相,均呈本征脆性。考虑晶格振动(声子)和电子激发的贡献后计算得到M2AB等压热容及热膨胀系数(TEC),均在300 K以下随温度升高先快速上升后上升速率逐渐降低,这与其它MAX相类似。较低的键刚度导致Zr系MAX相硼化物的平均线热膨胀系数整体上高于Hf系,而且在300~1300 K区间与大部分MAX和MAB相一致。Zr2SB,Hf2SB,Zr2SeB,Hf2SeB,and Hf2TeB are all recently discovered S-group elements containing MAX-phase borides,which attract much attention since the MAX phase borides are significantly unlike the typical MAX phases.Here,the phase stability,mechanical properties and thermal properties of MAX phase borides(M=Zr,Hf,A=S,Se,Te)were studied by using first principles and"linear optimization method",bond stiffness model and quasi-simple harmonic approximation.The results of the theoretical analysis were consistent with the currently available experimental results.Only M2AB was found to be stable after thermodynamic and intrinsic stability analysis.The shorter M−A bond and M−B bond lengths cause bond stiffness of Hf lineage higher than that of Zr,which also leads to the higher hardness of Hf lineage compound than that of Zr.the A site element goes from S to Se and to Te,the bond lengths of M−B and M−A are gradually increased,which lead to decrease in the elastic modulus.Moreover,the bulk modulus of these compounds is determined by their average chemical bond stiffness.Importantly,the high kmin/kmax(stiffness ratio of the weakest and the strongest bonds)shows that these MAX phases are inherently brittle,different from conventional MAX phase.Including the contribution of lattice vibration(phonon)and electron excitation,the isobaric heat capacity and heat expansion coefficient of M2AB increase rapidly with increasing the temperature below 300 K and then the rise rate gradually decreases,similar to other MAX phases.Lower bond stiffness results in an overall higher TEC of MAX phase borides in the Zr lineage than in the Hf lineage.The TEC values of these compounds in the 300−1300 K interval are consistent with most of the MAX and MAB phases.

关 键 词：第一性原理 MAX相硼化物 物相稳定性 力学行为 热学性能 

分 类 号：TQ134[化学工程—无机化工]