Crystallisation and sintering behaviour of nanocrystalline Y-TZP powders obtained by seeding-assisted chemical coprecipitation

Addition of nanometric-size Y-TZP seed particles to yttrium-zirconium cation sols resulted in a lowering (50 to 100 degrees C) of the air-crystallisation temperature of the Y-TZP (3 mol% Y2O3) phase, and a strong increase in the crystallisation rate (about one order of magnitude higher) for the formation of Y-TZP phase in air-calcined coprecipitated amorphous powders relative to the unseeded Y-TZP ones. The isothermal crystallisation rates for the Y-TZP formation in unseeded and polycrystalline Y-TZP seeded (10 wt%) Y-TZP amorphous precursors were well fitted by an Avrami-type kinetic relationship. Addition of nanometric-size Y-TZP seed particles to Y-TZP amorphous precursors reduced the apparent activation energy for the Y-TZP crystallisation process from 184 to 119 kJ mol(-1). Fully transformed seeded Y-TZP coprecipitated amorphous precursors (375 degrees C for 10 h) retained greater than or equal to 100 m(2) g(-1) surface area, and exhibited a mainly mesoporous structure with relatively narrow pore size distributions. Green compacts of such a Y-TZP powders sintered at near theoretical density at a temperature Bs low as 1050 degrees C for 5 h with a grain size within the nanoscale (< 100 nm). (C) 1999 Elsevier Science Limited and Techna S.r.l. Ali rights reserved.