Temperature behavior of the AlH3 polymorph by in situ investigation using high resolution Raman scattering

Area of Science:

• Materials Science
• Solid-State Chemistry
• Spectroscopy

Background:

• Aluminum hydride (AlH3) exists in multiple polymorphic forms.
• Understanding the distinct properties of each polymorph is crucial for material applications.
• Raman spectroscopy is a powerful tool for vibrational analysis and material characterization.

Purpose of the Study:

• To experimentally determine the characteristic Raman spectra of the alpha, beta, and gamma phases of aluminum hydride (AlH3).
• To provide a basis for the univocal assignment of spectral features to each specific AlH3 polymorph.
• To validate experimental findings through theoretical calculations.

Main Methods:

• Low-temperature (20 K) Raman spectroscopy under a helium atmosphere.
• Sequential thermal treatment to isolate individual AlH3 polymorphs (beta at 70 °C, gamma at 100 °C).
• Density functional theory (DFT) calculations for Raman spectra simulation.

Main Results:

• Distinct Raman spectra were experimentally obtained for the alpha, beta, and gamma phases of AlH3.
• Experimental spectra were successfully correlated with DFT-calculated spectra.
• Each AlH3 polymorph was unambiguously assigned its characteristic spectral features.

Conclusions:

• The study successfully differentiated and assigned Raman spectral features to individual AlH3 polymorphs.
• The combined experimental and theoretical approach provides a reliable method for polymorph identification.
• This work enhances the understanding of AlH3 solid-state chemistry and vibrational properties.