Our research group is at the forefront of developing rare earth ceramics with exceptional mechanical properties, focusing on materials like rare-earth orthophosphates, including GdPO4. These materials, known for their thermal and chemical stability, promise improved properties for high-performance applications in extreme environments as barrier and fiber coatings for advanced thermal protection systems and ceramic matrix composites. They also exist in natural forms as minerals in the earth where their deformation records geologic processes like asteroid impacts.

Why Rare Earth Ceramics?

Traditional materials face limitations in extreme environments, but rare earth ceramics confer unique chemical, thermal, and mechanical benefits, which can be optimized over a wide composition space. Our work investigates the unique deformation mechanisms in these materials, including twinning-based superelasticity, which enables remarkable recovery after stress. This discovery opens up new possibilities for enhancing the durability and toughness of materials exposed to high stress and temperature.

Uncovering the Effects of Non-Hydrostaticity on Pressure-Induced Phase Transformation in Xenotime-Structured TbPO4

Applications and Impact:

– Increasing Plasticity in Ceramics: Promotion of plastic deformation mechanisms allows absorption of energy to increase the durability of these ceramics. 
– Behavior Modification through Stress State Manipulation: Pressure-induced phase transformations can be substantially impacted by shear components in the stress state. Stress state manipulation allows for tailored triggering of phase transformation for crack arrest and creation of new non-equilibrium phases. 
– Stress History Monitoring: Structural distortion in these ceramics can encode the stress history experienced by the material, which could be useful for non-contact, non-destructive evaluation of engineering components in service.
– Understanding our World: Some of these same ceramics exist as mineral phases and knowledge of their plastic deformation can be used to infer the stress distributions imposed by asteroid impacts and land shifts, a field known as paleopiezometry, which assists in reconstructing geochronology, the study of the history of Earth’s rocks, minerals, and geologic events.

The Science:

If you thought mechanical behavior was all about metallurgy, you’re in for a treat with ceramics. Their high bond strengths and low symmetry can promote a rich plurality of slip and twinning systems that test your linear algebra and stereographic projection skills. We use a range of optical and mechanical spectroscopic techniques to characterize mechanical deformation and distortion of crystal structures. Specialized mechanical techniques allow exploration of a range of complex stress states.

Graduate students joining our group will engage with cutting-edge techniques like nanoindentation, diamond anvil cell in situ spectroscopy and x-ray diffraction, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) to understand and optimize these materials’ mechanical behavior. By contributing to the development of rare earth ceramics, you’ll be developing scientific understanding that spans from prehistorical geologic events to next-generation aerospace and outer space technologies.

Revealing Pressure Induced

Mechanical Behavior