The temperature dependence of the relative grain‐boundary energy of yttria‐doped alumina

Abstract

Abstract Atomic force microscopy was used to measure the dimensions of grain‐boundary thermal grooves on the surfaces of Al 2 O 3 , 100 ppm Y‐doped Al 2 O 3 , and 500 ppm Y‐doped Al 2 O 3 ceramics heated at temperatures between 1350°C and 1650°C. The measurements were used to estimate the relative grain‐boundary energies as a function of temperature. The relative grain‐boundary energies of Al 2 O 3 decrease slightly with increased temperature. When the doped samples were heated, there was an overall increase in the grain‐boundary energy, attributed to a reduction in the grain boundary excess at higher temperature. The overall trend of increasing grain‐boundary energy was interrupted by abrupt reductions in grain‐boundary energy between 1450°C and 1550°C. In the same temperature range, there is an abrupt increase in the grain‐boundary mobility that is associated with a complexion transition. When the 100 ppm Y‐doped sample was cooled, there was a corresponding increase in the relative grain‐boundary energy at the same complexion transition temperature, indicating that the transition is reversible.