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Tunable oxygen vacancy diffusion and electronic conduction through strain engineering in PZT films.
Betul Akkopru-Akgun1,2, Kathleen Coleman3, Arash Kazemi4
1Center for Dielectrics and Piezoelectrics, Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802, USA. bua134@psu.edu.
Scientific Reports
|August 8, 2025
Summary
Strain gradients in lead zirconate titanate films enhance electronic and ionic conductivity by reducing vacancy diffusion energy barriers. This improves performance in piezoelectric microelectromechanical systems utilizing bending for displacement.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Ceramics
Background:
- Lead zirconate titanate (PZT) ceramics are widely used in piezoelectric applications.
- Strain gradients can significantly alter material properties, but their impact on PNZT conductivity is not fully understood.
- Understanding these effects is crucial for optimizing piezoelectric microelectromechanical systems (PMUTs).
Purpose of the Study:
- To investigate the influence of strain gradients on the electronic and ionic conductivity of Nb-doped PZT (PNZT) films.
- To elucidate the mechanisms behind conductivity enhancement under bending strain.
- To assess the impact of these changes on ferroelastic domain behavior and dielectric properties.
Main Methods:
- Fabrication of Nb-doped PZT films.
- Application of controlled bending strain (0–0.5%) to PNZT films.
- Measurement of ionic conductivity (vacancy diffusion, mobile ion concentration) and electronic conductivity.
- Analysis of ferroelastic domain structure (a-domains, c-domains) and domain wall concentrations.
- Characterization of dielectric properties (Rayleigh coefficients).
Main Results:
- Increasing bending strain reduced vacancy diffusion energy barriers and increased mobile oxygen vacancy concentration, enhancing ionic conductivity.
- Strain-induced electric fields from flexoelectric and piezoelectric effects boosted electron trapping, increasing electronic conductivity.
- Bending strain promoted ferroelastic domain reorientation, increasing the volume fraction of a-domains and enhancing reversible and irreversible Rayleigh coefficients.
Conclusions:
- Strain gradients significantly enhance both electronic and ionic conductivity in PNZT films through vacancy diffusion and domain reorientation.
- These findings provide insights into optimizing PNZT-based devices, particularly piezoelectric microelectromechanical systems that rely on bending.
- The study highlights the critical role of strain engineering in tailoring the functional properties of ferroelectric materials.
