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 10Nb 2 O 5 -7.5La 2 O 3 -82.5Al 2 O 3 (volume fraction) composite ceramics prepared by microwave sintering were researched. The effect of microwave sintering processes on the grain growth kinetics of Al 2 O 3 columnar crystal were investigated, and the effect of sintering methods on the grain growth kinetics of Al 2 O 3 columnar crystal were analyzed by comparison with conventional sintering. The growth mechanisms of Al 2 O 3 columnar crystal in the composite ceramic were proposed. The results show that there are three phases of Al 2 O 3 , LaNbO 4 and Nb 2 O 5 in the composite ceramic, the grain growth kinetics exponents of Al 2 O 3 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 Al 2 O 3 columnar crystal is the wettability of liquid phase LaNbO 4 on grain boundaries under high temperature conditions. The grain growth kinetics exponents of the major axis and minor axis of Al 2 O 3 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 Al 2 O 3 columnar crystal in the composite ceramics.