Crystallite growth in yttria-doped superfine zirconia powders and their compacts: A comparison between Y-TZP and YSZ

Crystallite growth characteristics in Y-TZP (yttria-tetragonal zirconia polycrystals) and YSZ (yttria-stabilized cubic zirconia) powders and their compacts were compared. When holding at less than or equal to 1000 degrees C the crystallite size of Y-TZP is greater than YSZ both in powders and in compacted bodies, but the crystallites of YSZ grow faster than Y-TZP at elevated temperatures and the grain size of YSZ becomes larger when heated at 5 degrees C/min to above 1200-1250 degrees C or so, both in powders and in their compacts. It is proposed that this phenomenon results from the different crystallite surface or interface energy between different crystal phases, which affects the initial crystallite size in nucleation at crystallization temperature and crystallite/grain growth rates at higher temperatures.