What is the Definition of Sintered Alumina?

Sintered Alumina is a family of grains developed in the 1950s produced from unfused alumina. Several processes exist based on both raw bauxite and Bayer processed alumina. The most common is to use a feed material of raw bauxite milled to <5 mm. The mix with bonder is first extruded to produce rods which are cut into short cylinders or cones in the green state. They are then fired in rotary kilns at (1,350–1,500)oC using natural impurities in the bauxite as sintering agents . [1] The resulting grain is extremely tough especially at the relatively large sizes the technology allowed to be produced (8#–20#) and the material found great success, until the advent of zirconia alumina grain, in billet conditioning and other rough grinding operations. It is still used as a blend component with Zirconia Alumina.

Reference:
1. Wellborn W.W., AES Mag. 31(1) (1991) 6–13.