Ultra-low oxygen activity environment for metastable oxide phase synthesis
Abstract
Using extreme oxygen partial pressure environments (such as CaH2 and Mg-trap environments that can reach less than 10-20 atm P(O2) we will create oxygen-deficient compounds that are metastable and can hold far-from-equilibrium defect concentrations. Exposing oxide thin films such as VO2 and LaCoO3 to these environments at modest temperatures (less than500 ℃) we will investigate structural stability, electrical behavior and kinetics of phase transformations. The structural and functional properties of the metastable oxides will be characterized at various temperature-pressure anneal conditions to monitor phase formation and evolution of defect structures. Phase transformations under chemical potential perturbations, conductance and magnetic order transitions will be monitored. In addition, we will also fabricate local oxygen getters such as thin film Al or Zr capping layers that will remove oxygen ions from the underlying thin film oxide phase under electric fields to create metastable oxygen-deficient phases that can be studied in-situ as the reaction proceeds, and this will complement the studies conducted in annealing furnaces. Synchrotron scattering studies will be carried out real-time using in-operando sample holder to investigate the kinetics of transformation and frustrated lattice dynamics on representative samples. We will apply electrical and thermal stimulus on samples quenched under various conditions to investigate the thermodynamic driving forces necessary for sequential transformations that will directly probe the energy landscape. Combined, these studies will inform the use of extreme oxygen environments to create functional far-from-equilibrium metastable phases in oxides and their response to external fields that are of broad interest to the materials community.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 29, 2024
- Source ID
- FA95502310215
Entities
People
- Shriram Ramanathan
Organizations
- Air Force Office of Scientific Research
- Rutgers University
- United States Air Force