Non-uniform sintering of yttria-stabilized zirconia powder compact

Abstract

Abstract Sintering behavior in both axial and radial directions has been studied for both pure and doped 8 mol.% yttria stabilized zirconia (8YSZ) with different concentrations of lithium nitrate. Detailed measurements were conducted at different positions in radial and axial directions to study the spatial variation in sintering of the powder compact. Doping with lithium nitrate was used to study the effect of varying the sintering rate on the spatial variation of sintering. It was shown that variation in sintering strain in the axial direction is small, whereas a linear gradient is noticeable in the radial direction. The variation in radial strain peaks at relatively low strains (5 – 10 %) and reduces to a minimum at the end of sintering. Comparing average axial and radial strains showed that radial strain is consistently higher than axial strain, implying that sintering is anisotropic especially during the intermediate stage. Density is determined in two ways: (1) Calculated based on measured volumetric strain, (2) calculated assuming sintering is isotropic; the two quantities are compared. It is shown that density divergence can rise to as large as 15 % and nearly vanishes at the end of sintering.