Structural insights into M2O-Al2O3-WO3 (M = Na, K) system by electron diffraction tomography

Area of Science:

• Materials Science
• Crystallography
• Solid-State Chemistry

Background:

• The M2O-Al2O3-WO3 system shows promise for tunable solid-state lasers due to its near-IR transparency.
• Investigating these materials is difficult due to challenges in producing large, pure crystals and analyzing nanoscale, polycrystalline structures with pseudosymmetry.

Purpose of the Study:

• To present the structure investigation of two new compounds: K5Al(W3O11)2 and NaAl(WO4)2.
• To demonstrate the utility of electron diffraction tomography (EDT) for analyzing nanocrystalline phases, including those in polyphasic mixtures.

Main Methods:

• Utilized a combination of electron diffraction tomography (EDT) and precession electron diffraction.
• Employed automated diffraction tomography (ADT) to collect complete 3D electron diffraction data and minimize dynamical scattering effects.

Main Results:

• Successfully determined the crystal structures of K5Al(W3O11)2 and NaAl(WO4)2.
• Demonstrated that EDT can effectively identify symmetry and pseudosymmetry in nanocrystalline materials, even within complex mixtures.
• ADT proved suitable for ab initio structure solution and detecting pseudosymmetry missed by X-ray powder diffraction.

Conclusions:

• Electron diffraction tomography is a powerful tool for the ab initio structure solution of nanocrystalline materials.
• ADT overcomes limitations of traditional methods, enabling detailed structural analysis of challenging samples like those in the M2O-Al2O3-WO3 system.
• This work advances the understanding and potential application of these materials in laser technology.