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The electrical conductivity of Al2O3 under shock-compression
Hanyu Liu1, John S Tse2, W J Nellis3
1Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, S7N 5E2, Canada.
Scientific Reports
|August 5, 2015
Summary
Sapphire (Al2O3) remains transparent and non-conducting below 100 GPa. Shock compression above 500 GPa causes Al2O3 to melt into a metallic liquid, reaching thermal equilibrium.
Area of Science:
- Materials Science
- High-Pressure Physics
- Computational Condensed Matter Physics
Background:
- Sapphire (Al2O3) is used in dynamic compression experiments below 100 GPa.
- Shock compression above 100 GPa induces defects, causing opacity and electrical conductivity.
- These non-equilibrium effects hinder thermodynamic measurements.
Purpose of the Study:
- To predict and interpret shock experiments using electronic structure calculations.
- To identify a potential experimental window for sapphire up to 200 GPa.
- To determine the high-pressure, high-temperature thermodynamic properties of shocked Al2O3.
Main Methods:
- Electronic structure calculations were performed.
- Results were used to guide interpretation of shock compression experiments.
- Calculated conductivity was compared to experimental data for various materials.
Main Results:
- Shocked sapphire does not metallize by band overlap around 300 GPa.
- Al2O3 melts into a metallic liquid at approximately 500 GPa and 10,000 K.
- Conductivity increases to ~2000 Ω(-1)cm(-1) at ~900 GPa, indicating thermal equilibrium.
Conclusions:
- Sapphire's opacity and conductivity at ~100 GPa are non-equilibrium phenomena.
- Shock-compressed Al2O3 reaches a metallic liquid state at extreme pressures and temperatures.
- The conductivity of shocked Al2O3 aligns with other disordered, strongly scattering metallic fluids.
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