Preparation of alumina-high zirconia microcomposite by combined gel-precipitation

Microcomposites of alumina and zirconia containing equal volume fractions of the two are prepared by a combined gel-precipitation route using aluminium chloride and zirconium oxychloride as precursors. Dried gel powders calcined between 375 and 800 degreesC show cubic phase as the only crystalline phase, Zirconia gets converted to tetragonal phase above 900 degreesC and is retained mostly in this form upto 1000 degreesC. At the higher temperatures. it converts to the monoclinic phase. Alumina starts to crystallize into 6-form at 900 degreesC and is converted to a-form at 1250 degreesC. Pressed pellets sintered at 1400 degreesC achieve densities close to theoretical in 4 h. Microstructures show evidence of segregation and coarsening in a composite matrix of alumina and zirconia mixed at a submicron level. (C) 2002 Elsevier Science B.V. All rights reserved.