Dispersion Toughening in MgO-doped Tantalum Oxide

SEM micrograph of MgO-doped tantalum oxide fracture. Excess MgO dopant has precipitated as discreet magnesium tantalate inclusions within the oxide grains. The beautiful visual effects result from the deflection of the moving crack front by these inclusions, a phenomenon known as precipitate hardening or dispersion toughening. The photograph was taken in 1980 by me at MIT, and may represent the first documentation of the phenomenon in a refractory oxide.