Second-Phase Grain Boundary Engineering in Al₂O₃-MgAl₂O₄ Composites: Microstructure and Dielectric Breakdown...

Area of Science:

• Materials Science
• Ceramic Engineering
• Electrical Engineering

Background:

• Pulsed power technology and high-energy-density capacitors require advanced dielectric materials.
• Existing dielectric ceramics often lack the necessary combination of breakdown reliability and microstructural homogeneity.

Purpose of the Study:

• To fabricate and characterize Al2O3-MgAl2O4 composites for enhanced dielectric properties.
• To establish a correlation between microstructure, defect distribution, and dielectric breakdown strength.
• To optimize the composition for improved energy storage applications.

Main Methods:

• Solid-state reaction synthesis of Al2O3-MgAl2O4 composites with varying kaolin/MgO ratios.
• X-ray Diffraction (XRD) for phase analysis and spinel formation mechanism study.
• Scanning Electron Microscopy (SEM) for microstructural characterization (grain size, porosity).
• Weibull analysis for dielectric breakdown strength and reliability assessment.

Main Results:

• Optimal dielectric reliability achieved with the 4:1 kaolin/MgO ratio composite.
• Characteristic breakdown strength of 17.74 kV/mm and Weibull modulus of 16.07 for the 4:1 group.
• Microstructural optimization involved balancing grain boundary pinning and residual porosity.
• Excess MgO led to ionic conduction and premature breakdown due to Mg2+ in the glassy phase.

Conclusions:

• A quantitative correlation between microstructural composition, defect size distribution, and dielectric breakdown was established.
• The study provides a theoretical basis for optimizing low-cost alumina-based ceramics for energy storage.
• The developed composites show promise for advanced pulsed power and capacitor applications.