A new sintering aid for magnesium aluminate spinel

A dense MgAl2O4 sintered spinel has been prepared following a conventional double stage firing process. A new type of sintering aid, AlCl3, can improv e the bulk density, apparent porosity and water absorption of MgAl2O4 spine l sintered at 1550 degreesC devoid of any contamination. In order to see th e effect of AlCl3 on densification and formation of a MgAl2O4 spinel, 0.01- 0.03 mol.% AlCl3 was added separately prior to calcination, subsequent to c alcination as well as simultaneously at both stages. AlCl3 is found to be e qually effective in enhancing spinel formation during calcination as well a s in increasing sintered density. The efficacy of AlCl3 as a "spinelizer" o r as a sintering aid is also compared with the conventional mineralizer. Al F3, which is generally added only prior to calcination to enhance the spine l formation. AlCl3 is found to be active as a sintering aid provided the po wder contains some free Al2O3 and MgO and probably the hygroscopic nature o f AlCl3 is responsible for its effectiveness as a sintering aid. (C) 2001 E lsevier Science Ltd and Techna S.r.l. All rights reserved.