Phase stability of AlYB(14) sputtered thin films

Area of Science:

• Materials Science
• Solid State Chemistry
• Computational Materials Science

Background:

• AlYB(14) (Imma) thin films are synthesized using magnetron sputtering.
• X-ray diffraction confirms the presence of crystalline AlYB(14) without other phases.
• Compositional analysis reveals variable Al and Y occupancies.

Purpose of the Study:

• Investigate the effect of Al and Y occupancy on the stability of Al(x)Y(y)B(14) thin films.
• Determine the most stable configuration of Al(x)Y(y)B(14) using computational methods.
• Analyze charge transfer and distribution within boron icosahedra and its relation to stability.

Main Methods:

• Synthesis of AlYB(14) thin films via magnetron sputtering.
• Characterization using X-ray diffraction, electron probe microanalysis, energy dispersive X-ray analysis, and elastic recoil detection analysis.
• Density functional theory (DFT) based calculations to model Al(x)Y(y)B(14) configurations (x,y = 0.25, 0.5, 0.75, 1).

Main Results:

• The most stable configuration identified is Al(0.5)YB(14).
• This stable configuration involves a charge transfer of two electrons from metal atoms to boron icosahedra.
• Stability increases with more homogeneous charge distribution within the icosahedra.
• Calculated bulk moduli range from 196 to 220 GPa, comparable to hard phases like α-Al(2)O(3).

Conclusions:

• Al(0.5)YB(14) represents the most stable phase under the investigated conditions.
• Homogeneous charge distribution within boron icosahedra is crucial for enhancing the stability of Al(x)Y(y)B(14) materials.
• The calculated mechanical properties suggest potential applications for these materials in demanding environments.