Activation Energy for the Sintering of Two‐Phase Alumina/Zirconia Ceramics

In an earlier paper we reported measurements of the activation energy for sintering from constant‐heating‐rate experiments with alumina/5% zirconia. Here, results from a full range of compositions in this two‐phase system are described. They show that the activation energy remains in the range 700 ± 100 kJ/mol when the composition changes from 5 to 95 vol% zirconia. In comparison, pure zirconia sinters with an activation energy of 615 ± 80 kJ/mol and pure alumina with the energy of 440 ± 45 kJ/mol. The addition of 2.8 mol% yttria to zirconia does not have a measurable effect on the activation energy. The grain size dependence of the sintering rate suggests boundary‐diffusion‐controlled sintering. These activation energies are phenomenologically correlated with the interfacial energies in alumina, zirconia, and two‐phase alumina/zirconia, suggesting that the bonding at the interface influences diffusional transport.