Effect of compositional variation and fineness on the densification of MgO-Al2O3 compacts

Single stage densification of magnesia-alumina compacts were studied with MgO to Al2O3 molar ratios 1:1 (stoichiometric spinel), 2:1 (magnesia rich spinel) and 1,2 (alumina rich spinel). Attritor milling has been adopted to produce variation in fineness. Milling greatly improved the densification. Densification was found to be easier for the magnesia rich composition and difficult for the alumina rich one. Xray diffraction patterns showed the expected phases in stoichiometric and magnesia rich spinel. Alumina rich composition showed no free corundum phase on sintering at 1650 degrees C and only spinel phase marks the complete solid solution of excess alumina in spinel at this composition. EDAX analysis also supports the event and also reflects that the impurities are mainly present at the grain boundaries. (C) 1999 Elsevier Science Ltd. All rights reserved.