Polymorphism in Strontium Tungstate SrWO₄ under Quasi-Hydrostatic Compression.

Area of Science:

• Materials Science
• Solid State Physics
• Crystallography

Background:

• Strontium tungstate (SrWO4) is a material with potential applications in various fields.
• Understanding its structural behavior under extreme conditions is crucial for predicting its properties.
• Previous studies have explored its properties, but a comprehensive understanding of its high-pressure phases is lacking.

Purpose of the Study:

• To investigate the structural and vibrational properties of SrWO4 under high pressure.
• To identify and characterize the polymorphs and phase transitions of SrWO4 up to 46 GPa.
• To elucidate the structural mechanism of pressure-induced transformations in SrWO4.

Main Methods:

• Angle-dispersive synchrotron X-ray diffraction (XRD) up to 27 GPa.
• Raman spectroscopy measurements up to 46 GPa.
• Ab initio calculations to support experimental findings and predict theoretical phases.

Main Results:

• Four polymorphs of SrWO4 were identified under quasi-hydrostatic compression.
• Three distinct phase transitions were observed at 11.5 GPa, 19.0 GPa, and 39.5 GPa.
• The ambient scheelite-type structure transforms to a monoclinic fergusonite-type structure at 11.5 GPa, followed by other monoclinic and orthorhombic phases.

Conclusions:

• The fergusonite-type phase acts as a structural bridge between low- and high-pressure phases.
• The study reveals a transition from [WO4] tetrahedra to [WO6] octahedra at higher pressures.
• Experimental and computational data provide a comprehensive understanding of SrWO4's high-pressure structural systematics.