Dislocations in oxides can be heavily charged, providing the possibility for tailoring functionalities of these materials. Charged dislocations could: i) tune the charged barrier for thermal/electrical scattering; ii) serve as pinning center for domain walls in ferroelectrics; iii) provide sites for enhanced transport and reaction rate owing to the local distortion. The desired properties can only be harvested if strategies can be made available to generate and control dislocations in oxides. Our mission is to understand the dislocation behavior in oxides, to develop new methods for dislocation induction and control in oxides, and ultimately to evaluate the dislocation-tuned functionalities in oxides.
- Dislocation behavior in oxides:
We mechanically introduce dislocations into oxide ceramics over a large temperature range by plastic deformation. We study the dislocation nucleation, multiplication, and mobility in different oxides at different length scales. At microscale, nanoindentation and micro-scratch tests are employed for site-specific investigation of the dislocation nucleation and arrangement. At macroscale, high temperature deformation experiments (e.g., creep) are carried out to introduce and control the dislocation networks in the bulk materials. The dislocations are characterized using chemical etching, SEM, EBSD, TEM, and dark-field X-ray microscopy, etc.
- Dislocation-tuned functionality:
By controlling the dislocation networks in the oxide ceramics, it is expected to influence the thermal conductivity, ionic conductivity, or electrical conductivity of the materials. In ferroelectrics, the dislocations are expected to pin the domain walls, hence result in “piezoelectric hardening”. We evaluate these properties via conductivity measurement, impedance spectroscopy, resonance measurements, etc.
