Sintering kinetics of 8Y-cubic zirconia:: Cation diffusion coefficient

Zirconia ceramics, mainly of cubic phase, are used in different applications because of their particular electrical and structural properties. After the forming stage, sintering leads to a material with suitable microstructural characteristics. The sintering process mainly depends on thermal cycle and on starting particle size and its distribution; it also depends on density and the microstructure of green material. Cubic zirconia has a high (2680 degrees C) melting temperature; however, effective sintering could be observed for temperatures higher than 900 degrees C (nanoparticles), and it may reach a final density of 96-98% the theoretical value at relative low temperatures. The objective of this paper is to study the sintering kinetics of stabilized zirconia in its cubic phase with 8% molar of Y2O3 under fast firing rates up to nearly isothermal conditions. Samples were shaped from suspensions dispersed with ammonium polyacrylate by slip casting. Sintering was performed in the temperature range between 1200 degrees C and 1400 degrees C. The sintering kinetic process was followed by measuring density as a function of time. A sintering model was applied to fit the experimental data of the first steps of densification. It was observed that sintering obeys the same mechanism in the temperature and time ranges under study, which results in an activation energy of 170 kJ mol(-1). Sintering is controlled by Zr cation diffusion, for which a lattice diffusion coefficient of D-1 = 8 x 10(-12) cm(2) s(-1) at 1400 degrees C was found, and the activation energy of the diffusion process was 223 kJ mol(-1). (C) 2008 Elsevier B.V. All rights reserved.