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Abstract : The main objective of the present study was to develop a high-strength machinable ceramic based on zirconia (ZrO 2) and magnesium aluminum silicate (Mg 3Al 2Si 6O 18; MAS) glass system through pressure-less sintering. Pressure-less sintering of ZrO 2, 3 mol% yttria-stabilized (YSZ) was carried out at 1450°C in air, using 10 wt% MAS glass as a sintering additive. The influence of glass on the microstructure and mechanical properties of the composite was investigated. The presence of glass into the ZrO 2 matrix was substantiated using scanning electron microscopy (SEM). X-ray diffractometry (XRD) revealed no crystalline phases other than tetragonal ZrO 2. The flexural strength of the composite was found to be ∼30% higher than YSZ. The apparent crack resistance was determined by Vickers microindentations carried out at different loads ranging from 9.8 to 196 N. The apparent crack length on the surface at each load was found to be decreased (6-21%) in YSZ and the corresponding crack-resistance values increased by about 5-20%. Both YSZ and composite showed rising trend in crack-resistance values as the indentation load was increased. Improved properties of composite sample were attributed to the formation of a relatively larger process zone surrounding the crack, crack-arrest behavior due to the localized compressive stresses, and the crack-bridging phenomena. © The Author(s) 2011 Reprints and permissions: sagepub.co.uk/journalsPermissions. nav.