The sintering of fine-grained α-alumina by spark plasma sintering (SPS) was performed to study grain growth under SPS conditions. Grain growth is found to be extensive at relative densities above 95%. A grain growth versus dwell time analysis during SPS allows for the determination of the grain-boundary diffusion coefficient. This study shows that the remarkable enhancement of grain-boundary diffusion derived from a previous analysis could be a consequence of the presence of the recently discovered “disconnections” at the grain boundaries of α-alumina. Their presence, together with their electric charge and the external electric field at the boundaries, are the key ingredients for a violation of the typical grain growth kinetic law. When they are introduced appropriately, an updated value of the grain-boundary diffusion coefficient is achieved. A comparison with other values reported previously in the literature through other techniques and a critical analysis are also carried out.

The authors acknowledge Nippon Steel & Sumitomo Metal Corporation, Japan for the doctoral thesis financial support awarded to Y. Tamura. They also acknowledge the financial support provided by the project from the Spanish ministry of Economy (MINECO) MAT-2015-71411-R as well as through a contract for Dr. Zapata-Solvas from the JAE-DOC program of CSIC, Spain. Dr. B. M. Moshtaghioun wants to acknowledge the financial support provided by the Spanish MINECO through the "Juan de la Cierva-Incorporación" contract during her postdoctoral stay in CSIC-Universidad de Zaragoza, Spain. The authors also acknowledge some financial support from the regional government "Junta de Andalucía" P12-FQM-1079.

Peer reviewed