Realization of diversity in physical properties of Zr₂Se(B_1‐xSe_x) MAX phases through DFT approach

Abstract

The discovery of a series of MAX phases, Zr2Se(B1‐xSex), with Se at both A‐ and X‐sites, drives a new chemical diversity to the MAX family. Here, we employed the density functional theory (DFT) approach to realize the diversity in physical properties of Zr2Se(B1‐xSex). All compositions of Zr2Se(B1‐xSex) are mechanically stable and the dynamical stability of the end member Zr2SeSe is confirmed. The elastic constant C33 and bulk moduli B show a decrease almost monotonically with Se‐content x while other constants and moduli change irregularly. All elastic constants and moduli except C12 and C13 are highest for the end member Zr2SeB. Additionally, the Vickers hardness, Debye temperature, minimum thermal conductivity, and lattice thermal conductivity are highest for Zr2SeB. The increase of Se‐content x at X‐site reduces most of the properties of Zr2Se(B1‐xSex). The electronic band structures change drastically with increasing Se‐content x. This diversity in electronic band structures is mainly the reason for the diversity in physical properties of Zr2Se(B1‐xSex). All compositions of Zr2Se(B1‐xSex) have the potential to be thermal barrier coating materials, and Zr2SeB has the potential to be etched into 2D MXene, Zr2B.

Role of Chalcogen Atoms as an A-Site Element on the Physical Properties of 211 MAX Phases in the Hf–A–B System

“…In a previous study, we observed that the Gou model provides hardness values similar to the experimental results if the M–A bond is excluded . Moreover, in a recent paper, we found a good matching of hardness from E with the experimental value . If the Hf–S bond is not taken into account, the Gou model gives a hardness value of 3.18 GPa for Hf 2 SB.…”

“…For evaluating θ D of partially ceramic crystals such as the MAX phase, the Anderson method has been found to be best suited and which formulate its mathematical expression as θ D = ( h / k B )­(3 n ρ N A /4π M ) 1/3 v m , in which h , k B , n , ρ, π, N A , and M are the most familiar symbols in Physics and Chemistry and v m is the average sound velocity that can be calculated from the transverse and longitudinal velocities v t and v l by v m = [1/3­(1/ v l 3 + 2/ v t 3 )] −1/3 . The transverse and longitudinal velocities v t and v l can be calculated from the bulk modulus B , shear modulus G , and mass density ρ by v l = [(3 B + 4 G )/3ρ] 1/2 and v t = [ G /ρ] 1/2 , respectively.…”

“…For evaluating θ D of partially ceramic crystals such as the MAX phase, the Anderson method 45 has been found to be best suited 46 and which formulate its mathematical expression as S5 and are shown in Figure 6a. The Debye temperature decreases when the A-site element S of Hf 2 SB is replaced by Se and then by Te, as is also the case for the sound velocities.…”

“…32 Moreover, in a recent paper, we found a good matching of hardness from E with the experimental value. 46 If the Hf−S bond is not taken into account, the Gou model gives a hardness value of 3.18 GPa for Hf 2 SB. This value is similar to the value obtained from E but breaks the trend of the change of hardness with chalcogen atoms.…”

Fabrication of Nano-sized Cr2GaC with a Bottom-Up Approach for Lithium Storage

“…A family of layered transition-metal carbides or/and nitrides, called MAX phases (short for M n +1 AX n and usually, n = 1, 2, or 3), where M is an early transition metal, A is often from groups 13–16, and X is C and/or N, − have raised much attention due to their intrinsically integrated metallic and ceramic properties, which endows them with potentials for multidisciplinary applications. − In addition, recently, there have been many studies on MAB, , a layered material similar to MAX phases. Moreover, the A-site atoms usually possess superior capacities for lithium storage, and the robust MAX matrix could enable a satisfactory cyclic life. − However, the conventional synthesis strategies often result in large particles, which leads to underutilization of active sites and poor electrical contact between particles, ultimately limiting its comprehensive electrochemical performance.…”