Nanoscale Phase Mixture and Multifield-Induced Topotactic Phase Transformation in SrFeO_x

Area of Science:

• Materials Science
• Solid-State Chemistry
• Nanotechnology

Background:

• Nanoscale phase mixtures in transition-metal oxides (TMOs) are crucial for emergent functional properties.
• Strontium iron oxide (SrFeO_x) exhibits distinct brownmillerite (BM-SFO) and perovskite (PV-SFO) phases with varied properties.

Purpose of the Study:

• To directly observe and manipulate nanoscale phase mixtures in SrFeO_x thin films.
• To investigate the structure-property correlations and multifield control of phase transformations.

Main Methods:

• Epitaxial thin film growth of SrFeO_x.
• Direct observation of nanoscale phase mixtures using advanced microscopy.
• Multifield manipulation (electric field, mechanical stress) of phase transformations.

Main Results:

• A nanoscaffold structure of PV-SFO nanodomains in a BM-SFO matrix was observed in pristine SrFeO_x films.
• Distinct electrical and electrochemical properties of BM-SFO and PV-SFO led to gridlike patterns in property maps.
• Reversible topotactic phase transformations between BM-SFO and PV-SFO were achieved using electric fields and mechanical stress.

Conclusions:

• A strong nanometric structure-property correlation exists in mixed-phase SrFeO_x.
• Multifield control offers a new paradigm for manipulating topotactic phase transformations in TMOs.
• Potential for novel device applications based on controlled phase switching.