Estimation of stress generated during co-sintering of porous and dense alumina layers

Abstract

Co-sintering was carried out in air at 1350°C for 1 hr to make two types of symmetrical 3-layered laminates. One is PDP (Porous alumina/Dense alumina/Porous alumina) laminate and another is DPD laminate. For the porous alumina layer, the porosity was set to be 20%; however, pore size was changed by adding three sizes of spherical mono-dispersed polymethyl methacrylate particles (5, 15, 30̄m) in raw alumina powder. Young's modulus measurements revealed that cracking occurred in both PDP and DPD laminates. The stress in the layer was estimated from an elastic calculation by using the mechanical and thermal expansion properties of each monolayer. In consideration of sintering shrinkage and thermal expansion of the layer, it was suggested that cracking occurred in the dense alumina layer during heating from 1000 to 1200°C, and in porous alumina layer during heating from 1200 to 1350°C. The cracking was mainly attributed to the mismatch of sintering shrinkage between the layers. From the discussion, the elastic model gave an explanation to crack formation during co-sintering.©2013 The Ceramic Society of Japan. All rights reserved.