Study on the growth kinetics of Al2O3 columnar crystal in Al2O3 matrix composite ceramics prepared by microwave sintering

Abstract

In this paper, the grain growth kinetics of 10Nb2O5-7.5La2O3-82.5Al2O3 (volume fraction) composite ceramics prepared by microwave sintering were researched. The effect of microwave sintering processes on the grain growth kinetics of Al2O3 columnar crystal were investigated, and the effect of sintering methods on the grain growth kinetics of Al2O3 columnar crystal were analyzed by comparison with conventional sintering. The growth mechanisms of Al2O3 columnar crystal in the composite ceramic were proposed. The results show that there are three phases of Al2O3, LaNbO4 and Nb2O5 in the composite ceramic, the grain growth kinetics exponents of Al2O3 columnar crystal in the composite ceramics decrease with the increase of sintering temperature, and the growth activation energies increase with the increase of holding time; the grain growth kinetics exponents in the minor axis direction are larger than those in the major axis direction. The decisive factor for the growth rate of Al2O3 columnar crystal is the wettability of liquid phase LaNbO4 on grain boundaries under high temperature conditions. The grain growth kinetics exponents of the major axis and minor axis of Al2O3 columnar crystal during microwave sintering are lower than those of conventional sintering. Therefore, the microwave sintering technology is superior to conventional sintering technology in promoting the growth of Al2O3 columnar crystal in the composite ceramics.