Influence of morphology and chemical surface composition on electrical conductivity of SiC microspheres

• Published in: Surface science Vol. 715; p. 121942
• Main Authors: Pleșa, Ilona, Radl, Simone, Schichler, Uwe, Ramsauer, Franz, Ladstätter, Werner, Bergmann, Irmgard, Kern, Wolfgang, Schlögl, Sandra
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-01-2022; Elsevier BV
• Subjects: Annealing; Chemical composition; Comparative studies; Composite materials; Current voltage characteristics; Electric components; Electric contacts; Electrical properties; Electrical resistivity; Microspheres; Morphology; Service life assessment; SiC microspheres; Sintering; Sintering aids; Surface modification; Thermal annealing; X ray photoelectron spectroscopy; Surface modification; SiC microspheres; Electrical properties; Thermal annealing
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2021.121942

•Electrical resistivity of spherically shaped SiC microspheres is studied.•An insulating SiO2 layer is formed at an annealing temperature of 650 °C.•Densely sintered SiC particles show non-linear current-voltage behavior.•Porous SiC particles follow linear current-voltage characteristics.•The immobilization of organosilanes leads to a higher volume resistivity.
The present work provides a comparative study on the electrical properties (i.e. current-voltage characteristics) of spherically shaped SiC micro-sized particles that have been prepared by a thermal sintering process. As a typical field grading material, SiC exhibits a non-linear current-voltage behavior, which is exploited to reduce electrical stresses within composite materials. This is of particular interest in high-voltage applications to avoid material breakdown and to enhance the electrical components’ lifetime. As the current-voltage characteristics are affected by transport mechanisms at the grain contact, the electrical performance can be controlled by changing the chemical surface composition and morphology of the SiC particles. Advancing from irregular SiC flakes, the current work focuses on the electrical properties of SiC microspheres that have been tailored by applying selected thermal annealing steps and by chemical surface functionalization with organosilanes. The chemical surface composition of the microspheres prior to and after the modification step was studied by XPS and EDX, whilst SEM was employed to visualize the morphology of the particles’ surface and cross-section. In addition, the current-voltage characteristics were determined as a function of the particles’ morphology and chemical surface composition. The results clearly show that sintering aids, annealing temperature, morphology of particles and surface modification strongly govern the non-linear current-voltage behavior of SiC microspheres.
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