Ta-based 413 and 211 MAX phase solid solutions with Hf and Nb

Abstract

New bulk MAX phase-based ceramics were synthesized in the Ta-Hf-Al-C and Ta-Nb-Al-C systems. Specifically, (Ta1-x,Hfx)4AlC3 and (Ta1-x,Nbx)4AlC3 stoichiometries with x = 0.05, 0.1, 0.15, 0.2, 0.25 were targeted by reactive hot pressing of Ta2H, HfH2, NbH0.89, Al and C powder mixtures at 1550°C in vacuum. The produced ceramics were characterized in terms of phase composition and microstructure by X-ray diffraction, scanning electron microscopy, electron probe microanalysis and scanning transmission electron microscopy. The investigation confirmed the existence of such M-site solid solutions with low solute concentrations, as predicted by first-principles calculations. These calculations also predicted a linear trend in lattice parameter evolution with increasing Hf concentration, in agreement with the experimental results. In order to increase the low phase purity of the produced ceramics, Sn was added to form (Ta1-2 x,Hfx)4(Al0.5,Sn0.5)C3 and (Ta1-x,Nbx)4(Al0.5,Sn0.5)C3 double solid solutions, thus resulting in a higher content of the 413 MAX phase compounds in the produced ceramics.

Newly Synthesized Ta‐Based MAX Phase (Ta1−xHfx)4AlC3 and (Ta1−xHfx)4Al0.5Sn0.5C3 (0 ≤ x ≤ 0.25) Solid Solutions: Unravelling the Mechanical, Electronic, and Thermodynamic Properties

“…The deviation is less from the previously calculated theoretical values (Griseri et al [ 40 ] However, the increase of lattice constants due to Hf substitution is lower than that obtained by Griseri et al [ 40 ] The difference might be due to the different calculation methods used. Griseri et al [ 40 ] have used the supercell approach to model solid solutions and studied the solid solutions based on the special quasi‐random structures (SQS) method, whereas the VCA approach is used for this study to model the solid solutions. The supercell approach is rigorous and often more reliable, which needs high computational resources that are not possible in the current case due to the hardware limitations.…”

“…Table 1 represents the optimized lattice parameters of (Ta 1− x Hf x ) 4 AlC 3 and (Ta 1− x Hf x ) 4 Al 0.5 Sn 0.5 C 3 solid solutions along with the theoretical and experimental lattice constants of (Ta 1− x Hf x ) 4 AlC 3 obtained by Griseri et al [ 40 ] . The obtained lattice constants are in good agreement with the experimental values, where the deviations from experimental values are in the range of 1.9% to 2.5% for a and 1.12% to 1.39% for c .…”

“…Table 1 represents the optimized lattice parameters of (Ta 1Àx Hf x ) 4 AlC 3 and (Ta 1Àx Hf x ) 4 Al 0.5 Sn 0.5 C 3 solid solutions along with the theoretical and experimental lattice constants of (Ta 1Àx Hf x ) 4 AlC 3 obtained by Griseri et al [40] . The obtained lattice constants are in good agreement with the experimental values, where the deviations from experimental values are in the range of 1.9% to 2.5% for a and 1.12% to 1.39% for c. The deviation is less from the previously calculated theoretical values (Griseri et al [40] However, the increase of lattice constants due to Hf substitution is lower than that obtained by Griseri et al [40] The difference might be due to the different calculation methods used. Griseri et al [40] have used the supercell approach to model solid solutions and studied the solid solutions based on the special quasi-random structures (SQS) method, whereas the VCA approach is used for this study to model the solid solutions.…”

“…Recently, (Ta 1− x Hf x ) 4 AlC 3 and (Ta 1− x Nb x ) 4 AlC 3 solid solutions with x = 0.00, 0.05, 0.10, 0.15, 0.20, and 0.25 have been synthesized by Griseri et al [ 40 ] . They have also synthesized the Sn‐containing double solid solutions [(Ta 1− x Hf x ) 4 Al 0.5 Sn 0.5 C 3 and (Ta 1− x Nb x ) 4 Al 0.5 Sn 0.5 C 3 ].…”

Synthesis, phase purification and magnetic characterization of the (Cr1−x, Mnx)2AlC MAX-phase

“…6 Nowadays, except the common ternary M n+1 AX n phases, quaternary doped MAX-phases are being widely studied. This is possible since MAX-phases form either stable solid solutions on M-, 7,8 A- [7][8][9] and X-sites 10 or stable phases in out-of-((M 0 ,M 00 ) n+1 AlC n 0 ) and in-plane M 0 2=3 ; M 00 1=3 2 AlC chemically ordered compounds, denoted as o-MAX and i-MAX phases, respectively. 11,12 Such a variety of possible compositions and atomic arrangements allows for the tailoring the physical properties and functionalities of MAX-phases.…”