Deciphering the phase transition-induced ultrahigh piezoresponse in (K,Na)NbO₃-based piezoceramics

Area of Science:

• Materials Science
• Solid-State Physics
• Ceramics Engineering

Background:

• Lead-free piezoceramics are crucial for sustainable electronic devices.
• Developing materials with large electrostrain is a key challenge.
• Understanding phase transitions is vital for optimizing piezoelectric properties.

Purpose of the Study:

• To introduce phase change mechanisms in lead-free piezoceramics for enhanced electrostrain.
• To investigate the nature of electric field-induced phase transitions in (K,Na)NbO3 solid-solutions.
• To correlate volume changes during phase transitions with piezoelectric performance.

Main Methods:

• Atomic mapping of local polar vector.
• In situ synchrotron X-ray diffraction.
• Density functional theory calculations.
• Simultaneous recording of macroscopic longitudinal and transverse strain.

Main Results:

• Demonstrated an electric field-induced phase transition between orthorhombic and tetragonal phases in (K,Na)NbO3.
• Observed a dramatic volume change associated with the phase transition.
• Achieved a huge effective piezoelectric coefficient of 1250 pm V⁻¹ along specific crystallographic directions.
• Validated the phase transition through significant volume change and strain measurements.

Conclusions:

• Phase transition mechanisms are an effective strategy for harvesting large electrostrain in lead-free piezoceramics.
• This approach offers broader design flexibility for high-performance piezoelectric materials.
• Opens new possibilities for discovering advanced functional oxides.