Spark plasma sintering of a commercially available granulated zirconia powder: Comparison with hot-pressing

A commercially available granulated TZ3Y powder has been sintered by hot-pressing (HP). The 'grain size/relative density' relationship, referred to here as the 'sintering path', has been established for a constant value of the heating rate (25 deg. C min-1) and a constant value of the macroscopic applied pressure (100 MPa). It has then been compared to that obtained previously on the same powder but sintered by spark plasma sintering (SPS, heating rate of 50 deg. C min-1, same applied macroscopic pressure). By coupling the analysis of a sintering law (derived from creep rate equations) and comparative observations of sintered samples using transmission electron microscopy, a hypothesis about the densification mechanism(s) involved in SPS and HP has been proposed. Slight differences in the densification mechanisms lead to scars in the microstructure that explain the higher total ionic conductivity measured, in the temperature range 300-550 deg. C, when SPS is used for sintering.