LOW-TEMPERATURE SINTERING AND MICROSTRUCTURAL DEVELOPMENT OF NANOCRYSTALLINE Y-TZP POWDERS

Powders of yttria-doped tetragonal zirconia (3 mol%) with a narrow por e size distribution and ultrafine particle size (similar to 9 nm) have been prepared by the mixed organic + inorganic precursors coprecipita tion method The compaction behaviour of almost agglomerate-free calcin ed powders was studied, and their sintering behaviour using both isoth ermal and non-isothermal techniques was evaluated. Fully dense nanosca le ceramics with. an average grain size below 95 nm were obtained afte r sintering at 1200 degrees C for 20 min or at 1150 degrees C for 4 h. Several stages were identified in the whole densification process: it was found that a particle rearrangement process assisted by sintering pressure is the densification mechanism in the earlier sintering step (up to 800 degrees C), and grain boundary diffusion was the dominant mechanism for densification up to 1180 degrees C. Activation energy va lues of 130 +/- 20 and 300 +/- 40 kJ mol(-1), respectively, were calcu lated for these densification mechanisms. The almost complete absence of agglomerates in the calcined powders and the homogeneous pore struc ture of the green compacts are the two main factors leading to low-tem perature fully densified Y-TZP bodies. (C) 1996 Elsevier Science Limit ed.