Effects of sintering temperature on the characteristics of aluminum oxide ceramics obtained without pressure using sintering additives of the Al2O3‒SiO2‒CaO system

Abstract

The alumina ceramics with high compressive  strength were prepared by pressureless sintering, and the kaolinite and calcium carbonate were added as Al2O3‒SiO2‒CaO sintering additives. The effects  of  sintering  temperature on the volume shrinkage, bulk density, water absorption and compressive strength of the alumina ceramics were studied. The phase composition, crystal cell parameters, average grain size and microstructure of the ceramic were analyzed by XRD, SEM  and  EDS.  The  results  show  that the lattice tends to packed with the increase of sintering temperature. The bonding between grains is the most compact after sintering at 1700 ℃. The volume shrinkage increases with the increase of sintering temperature. The water absorption of alumina ceramics after sintering at 1700 °С reaches the minimum value of 0,06 %. The bulk density and compressive strength increase first and then decrease with the increase of sintering temperature. At 1700 ℃, optimized mechanical properties of alumina ceramics is obtained, with a bulk density  of  3,80  g/cm3 and a compressive strength of 1323 MPa. Ill. 10. Ref. 41. Tab. 4.