Structural-phase transformation kinetics during sintering of alumina ceramics using metastable nanopowders

A.S. Kaigorodov, V.R. Khrustov, V.V. Ivanov, A.I. Medvedev, A.K. Shtol'ts
2005 Science of Sintering  
The processes taking place during pressureless sintering of nano-metastable Al 2 O 3 , compacted up to high densities (0.7 of the theoretical density) using the magnetic pulsed method were studied. The influence of MgO, TiO 2 and ZrO 2 additives on the kinetics of Al 2 O 3 polymorphous transition, shrinkage and microstructure evolution during annealing at temperatures up to 1450°C has been studied. We have found that the process of annealing is two-staged starting with a polymorphous
more » ... morphous transition. Doping changes the starting temperature as well as the shrinkage depth at both stages. TiO 2 and ZrO 2 additives decrease the temperature of the onset of shrinkage, whereas MgO increases it. The best composition contained MgO in the series of examined types of ceramics with an α-Al 2 O 3 matrix. The positive role of Mg addition in the production of dense and hard Al 2 O 3 ceramics is related to the nature of Mg influence on the activation of diffusion processes in Al 2 O 3 , as well as to the way of uniform distribution of MgO dopant in the material. All these factors provide effective damping of diffusion processes and limit α-Al 2 O 3 crystal growth. Highly dense MgO, ZrO 2 and TiO 2 doped Al 2 O 3 ceramics with a grain size of 190, 220, and 250 nm and microhardness of 22, 17 and 17 GPa, correspondingly have been obtained.
doi:10.2298/sos0501035k fatcat:ze7omp6invf5xngveklfuazdqm