Microstructural evolution in nanocrystalline Y–TZP containing a silicate glass

Nanocrystalline yttria stabilized tetragonal zirconia polycrystal (NC–Y–TZP) powders were coated with a sodium strontium silicate glass using the sol-gel technique. The compact powders were sintered at 1400°C for 1 h resulting in dense nanocrystalline pellets with 5, 10 and 15 vol.% glass. Short pre-sintering heat treatment at 800°C caused the full stabilization of the tetragonal phase while long treatments led to the devitrification of the glassy phase. The mean grain size decreased from 196 nm in the glass-free specimen to 140, 110 and 100 nm in the specimens containing 5, 10 and 15 vol.% glass, respectively. The grain size distribution width also decreased with increase in the glass content. TEM revealed the morphological changes of the highly facetted polyhedral grains in the glass-free specimens into the round-shape grains with increase in the glass content. The effect of the glass on the phase formation, densification and microstructure have been discussed.