The nano-Grain Composite Model

Nanocrystalline ceramics exhibit novel electrical properties compared to their microcrystalline counterparts. Recent work in the Mason group has demonstrated that the models used to determine local electrical properties of microcrystalline ceramics cannot be applied to study nanocrystalline ceramics. Instead the group has developed a “nano-Grain Composite Model” (n-GCM) to extract local grain core and grain boundary conductivities and dielectric constants, as well as grain boundary thicknesses from AC-impedance spectra of nanoceramics. (AC-impedance spectroscopy is a non-destructive electrical characterization technique.) The n-GCM has been applied for the first time to study nanocrystalline yttria-stabilized zirconia; however, the technique is generally applicable to broad classes of electroceramics.

The above figure demonstrates the n-GCM analysis procedure, showing how local conductivities, dielectric constants, and grain core volume fraction are found for a given nanocrystalline sample. The Scanning Electron Microscope image shows nanocrystalline yttria-stabilized zirconia.