Beyond phase boundaries: atomic mechanisms governing structure and property variations in (K, Na)NbO₃-based...

Area of Science:

• Materials Science
• Solid State Chemistry
• Nanotechnology

Background:

• Chemical dopants significantly improve electrical properties of (K, Na)NbO3-based piezoceramics through phase boundary engineering.
• The precise mechanisms behind these property enhancements remain incompletely understood.

Purpose of the Study:

• To elucidate the multi-scale mechanisms governing phase boundary engineering in lead-free piezoceramics.
• To establish a framework for designing high-performance, eco-friendly piezoceramics.

Main Methods:

• Comprehensive multi-scale structural analysis including neutron pair distribution function analysis and scanning transmission electron microscopy.
• First-principle calculations and phase-field simulations were employed.
• Investigated two representative solid-solutions: (K, Na, Li)NbO3 and (K, Na)NbO3-(Bi0.5Na0.5)ZrO3.

Main Results:

• Distinct atomic-scale mechanisms were identified for phase boundary engineering in the studied materials.
• In (K, Na, Li)NbO3, Li atom displacements induce a combined displacive and order-disorder phase transition.
• In (K, Na)NbO3-(Bi0.5Na0.5)ZrO3, Bi atom displacements lead to a predominantly order-disorder phase transition.
• Atomic-scale structures were correlated with mesoscopic ferroelectric domains and macroscopic electrical properties.

Conclusions:

• This work clarifies the role of chemical dopants in phase boundary engineering from a multi-scale perspective.
• The findings provide a foundation for designing lead-free piezoceramics with superior electrical properties.
• Advances the development of environmentally friendly piezoelectric materials.