Varistor Grain Boundary Characterization by High Resolution Analytics

A novel method for the characterization of complementary parameters of single varistorgrain boundaries is proposed. The influence of grain orientation mismatch on the electricalbehaviour is discussed. Therein, electrical parameters (Current-Voltage (I-V) characteris-tic), microstructural parameters (Electron Backscatter Diffraction (EBSD) scan), and thechemical composition (Atom Probe Tomography (APT), via a Focused Ion Beam (FIB)Lift-Out) are measured. Electrical measurements of different grain boundaries are analysedand categorized according to their grain boundary misorientation. APT scans of bulk ma-terial, a parameter study as well as two complete characterizations of grain boundaries arepresented. I-V characteristics show asymmetry depending on the polarity of the interface.Concentration profiles of comprised elements are shown and an asymmetrical oxygen-zincprofile is showcased for both grain boundaries. APT measurements show heightened bismuthconcentration in the grain boundary. Cobalt only shows a peak in concentration in the grainboundary with an asymmetrical I-V characteristic, all other dopant elements show uniformbehaviour for both grain boundaries.