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The Jahn-Teller effect in Cr5+ -doped PbTiO3: a multi-frequency electron paramagnetic resonance study
R Böttcher1, A Pöppl, J Hoentsch
1Fakultät für Physik und Geowissenschaften, Universität Leipzig, Linnéstraße 5, D-04103 Leipzig, Germany.
Summary
Electron paramagnetic resonance (EPR) spectroscopy reveals how Cr5+ defects in PbTiO3 ceramics are affected by temperature and electrical polarization. The Jahn-Teller effect and ferroelectric polarization influence the local symmetry and EPR spectra of these defects.
Area of Science:
- Solid State Physics
- Materials Science
- Spectroscopy
Background:
- Lead titanate (PbTiO3) is a ferroelectric perovskite with potential applications in electronic devices.
- Chromium (Cr5+) ions can be incorporated as defects in PbTiO3, influencing its properties.
- Electron paramagnetic resonance (EPR) is a powerful technique for studying defects with unpaired electrons.
Purpose of the Study:
- To investigate the behavior of Cr5+ defects in PbTiO3 ceramics using EPR spectroscopy.
- To understand the influence of temperature and ferroelectric polarization on the local symmetry of Cr5+ defects.
- To characterize the Jahn-Teller effect and its interplay with the ferroelectric phase in PbTiO3.
Main Methods:
- Electron paramagnetic resonance (EPR) spectroscopy was performed on powdered PbTiO3 ceramics containing Cr5+ defects.
- Measurements were conducted over a temperature range of 50-400 K at various microwave frequencies (X, Q, and W bands).
- Analysis focused on spectral changes, g-tensor contributions, and symmetry distortions.
Main Results:
- The Jahn-Teller effect stabilizes a tetragonally distorted Cr(5+)O6 octahedron with D(4h) symmetry.
- Ferroelectric polarization in PbTiO3 introduces an additional g-tensor contribution, with symmetry dependent on polarization orientation.
- Anisotropic EPR spectra at low temperatures transition to a motionally averaged isotropic spectrum above 200 K due to increased thermal motion.
Conclusions:
- The study elucidates the complex interplay between the Jahn-Teller effect, ferroelectric polarization, and Cr5+ defect symmetry in PbTiO3.
- EPR spectroscopy effectively probes the local structural and electronic environment of defects in ferroelectric materials.
- Temperature-dependent spectral changes provide insights into the dynamic behavior of these defects.
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