Interphase boundary, grain boundary, and surface diffusion in Al2O3-GdAlO3 composites determined from bicrystal coble creep experiments

Abstract

Small-scale in situ transmission electron microscopy-based Coble creep experiments were performed on Al2O3-GdAlO3 composites using localized laser heating. A primary goal of the work was to isolate the Al2O3-GdAlO3 interphase boundary diffusivity in order to understand how it contributes to the average properties of the composite. The diffusivities of the grain boundaries (GB) of GdAlO3 (GAP) and Al2O3 were measured to be DGb,GAP=15±14exp−580,000±62,000Jmol−1RTm2s−1, and DGB,Al2O3=25±21exp−542,000±30,000Jmol−1RTm2s−1, respectively. The average interphase boundary (IPB) diffusivity exceeds that of the grain boundaries and was measured to be DIPB=15±14exp−559,000±117,000Jmol−1RTm2s−1. Capillary smoothing experiments after creep were used to determine surface (S) diffusivities, DS,Al2O3=3.2x103±2.7x103exp−539,000±26,000Jmol−1RTm2s−1 and DS,GAP=4.6x104±7.7x10−6exp−625,000±82,000Jmol−1RTm2s−1. This works demonstrates the feasibility of small-scale Coble creep experiments to directly measure individual components of grain boundary and IPB diffusivities in composites.