Grain boundaries typically dominate fracture toughness, strength, slow crack growth of ceramics. To
improve these properties through mechanistically informed grain boundary engineering, precise
measurement of the mechanical properties of individua
l boundaries is essential, although this is
rarely achieved due to its complexity. Here we present a new approach to characterise the fracture
energy at the lengthscale of individual grain boundaries and demonstrate this capability with
measurement of the
surface energy of silicon carbide (SiC) single crystals. We perform experiments
using an
in situ
scanning electron microscopy based double cantilever beam test, thus enabling
viewing and measurement of stable crack growth directly. These experiments correl
ate well with our
density functional theory (DFT) calculations of the surface energy of the same SiC plane.
Subsequently, we measure the fracture energy for a bi
-
crystal of SiC, diffusion bonded with a thin
glassy layer. These measurements ultimately promo
te microstructural engineering of novel and
advanced ceramics.