Estimation of Stress Exponent and Activation Energy for Rapid Densification of 8 mol% Yttria‐Stabilized Zirconia Powder

Abstract

The rapid densification behavior of 8 mol% Y2O3‐stabilized ZrO2 polycrystalline (8Y‐SZP) powder compacts at the initial stage of pressure sintering (relative density (ρ·) below 0.92) has been investigated using an electric current‐activated/assisted sintering (ECAS) system. Data points corresponding to a fixed heating rate were extracted from the densification rate (ρ·) versus ρ and ρ· versus temperature (T) curves. These curves were obtained experimentally by consolidation at a fixed current. Under fixed current ECAS, the heating rate (T·) decreases continuously over sintering time. Using a quasi‐ constant heating rate (CHR) method, data points were extracted to plot ρ· vs. ρ, ρ· vs. T, and ρ vs. T curves at a fixed T·. The stress exponent (n), estimated from a log‐log plot of grain size (d)‐corrected ρ·/ρ and effective stress (σeff) at 1300–1400 K, shows an almost constant value of 1. In addition, the activation energy (Q) for rapid densification, estimated from an Arrhenius plot of d‐corrected ρ·/ρ also shows an almost constant value of 350 kJ/mol, which is considerably lower than the previously reported value of the activation energy for Zr4+ lattice diffusion of about 440 kJ/mol. These results suggest that rapid densification of 8Y‐SZP by ECAS seems to proceed by diffusional creep controlled by grain‐boundary diffusion of Zr4+ ions.

Study of the densification and grain growth mechanisms occurring during spark plasma sintering of different submicronic yttria-stabilized zirconia powders

“…The difference of sintering mechanism can be explained by the application of a higher macroscopic stress (100 MPa) in the present study. In literature, all stress exponent determinations are performed at a low sintering pressure (<100 MPa) [10,52,53]. Studies at higher pressures (>100 MPa) are conducted on cubic zirconia single crystals for high temperature creep purpose and evidenced creep by dislocation climb (n > 3) or plastic deformation (n > 4.5) [54][55][56].…”

High-temperature Pressurized Sintering of Yttria-stabilized Tetragonal Zirconia Powder Compacts by 28-GHz Microwave Irradiation

“…where A is a constant, G eff is the shear modulus of the compact, b is the Burgers vector, d is the grain size, p is the apparent grain size exponent, k is Boltzmann's constant, σ eff is the effective stress acting on the compact, D 0 is the frequency factor, Q is the apparent activation energy, and R is the gas constant. Based on results concerning about the room-temperature effective shear modulus for a porous 3Y-TZP 8) and the temperature dependence of shear modulus for a bulk 3Y-TZP 9) , the high-temperature effective shear modulus (G eff ) is calculated as follows 7,10) :…”

Materiales nanoestructurados de zirconia: Materiales densos y compositos con nanotubos de carbono (NTC)

“…En reportados en la literatura para la zirconia cúbica (Kumagai, 2013;Rajeswari et al, 2013), y está por debajo de los valores encontrados por este mismo método en materiales de 3YZ (Caruso et al, 2010;Mazaheri et al, 2009b) y Al2O3 (Su and Johnson, 1996;Wang and Teng, 2010).…”