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Effect of Current on Diffusivity in Metal Hexaborides: A Spark Plasma Sintering Study.
James T Cahill1, Victor R Vasquez2, Scott T Misture3
1Department of Mechanical and Aerospace Engineering, University of California, San Diego , La Jolla, California 92093-0411, United States.
ACS Applied Materials & Interfaces
|October 7, 2017
Summary
Pulsed direct current enhances metal ion diffusion in CaB6-SrB6 systems. Metal vacancies move towards the positive electrode, increasing Ca2+ and Sr2+ diffusivity at high temperatures.
Area of Science:
- Materials Science
- Solid-state Chemistry
- Physical Chemistry
Background:
- Calcium hexaboride (CaB6) and strontium hexaboride (SrB6) form solid solutions.
- Understanding ion diffusion is crucial for developing advanced materials.
Purpose of the Study:
- To investigate the effect of pulsed direct current (DC) on metal ion diffusion in CaB6-SrB6 diffusion couples.
- To quantify the enhanced diffusion rates and identify the underlying mechanisms.
Main Methods:
- Fabrication of CaB6-SrB6 diffusion couples.
- Application of pulsed DC (2.2 kA) at high temperature (2007 K).
- Analysis using energy-dispersive spectroscopy (EDS) and fitting diffusion profiles with error functions.
Main Results:
- Pulsed DC significantly enhanced Ca2+ and Sr2+ diffusion towards the positive electrode.
- Ca2+ diffusion into SrB6 showed a 3.8× enhancement, while Sr2+ into CaB6 showed a 1.8× enhancement.
- Enhanced mobility was attributed to the migration of negatively charged metal vacancies.
Conclusions:
- Pulsed DC is an effective method to control and enhance metal ion diffusion in hexaboride systems.
- The phenomenon is driven by the directed movement of vacancies under an electric field.
- Results provide insights into ion transport mechanisms in solid solutions.
