Processing of porous yttria-stabilized zirconia tapes: Influence of starch content and sintering temperature Marı ´a P. Albano a, * , Liliana B. Garrido a , Kevin Plucknett b , Luis A. Genova c a Centro de Tecnologı ´a de Recursos Minerales y Cera ´mica (CETMIC), C.C. 49 (B1897ZCA), M. B. Gonnet, Provincia de Buenos Aires, Argentina b Department of Process Engineering and Applied Science, Dalhousie University, 1360 Barrington Street, Halifax, Nova Scotia B3J 1Z1, Canada c IPEN-Instituto de Pesquisas Energe ´ticas e Nucleares, Av. Lineu Prestes 2242, Cidade Universitaria, CEP: 05508-000, Sa ˜o Paulo, Brazil Received 3 July 2008; received in revised form 1 September 2008; accepted 1 October 2008 Available online 21 October 2008 Abstract The tape-casting process was used to produce porous yttria-stabilized zirconia (YSZ) substrates with volume fractions of porosity ranging from 28.9 to 53 vol.% by using starch as a fugitive additive. Concentrated aqueous YSZ slips with different amounts of starch and an acrylic latex binder were prepared. The influence of the volume fraction of starch and sintering temperature on the sintering behavior and final microstructure were investigated. The microstructure consisted of large pores created by the starch particles with lengths between 15 and 80 mm and smaller pores in the matrix with lengths between 0.6 and 3.8 mm. The pores in the matrix reduced the sinterability of the YSZ leading to the retention of closed porosity in the sintered tapes. The porosities were above those predicted for each of the starch contents. However, larger deviations from the predicted porosity were found as more starch was added. The open to total porosity ratio in the sintered tapes could be controlled by the volume fraction of added starch as well as by the sintering temperature. As the volume fraction of starch increased from 17.6 to 37.8 vol.% there was a gradual increase in the interconnectivity of the pore structure. The sintering shrinkage of the tapes at a given temperature could be directly related to the YSZ packing density in the matrix. # 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: A. Tape casting; Porous ZrO 2 ; Green and sintered properties 1. Introduction Porous ceramics find application in a variety of components, including fuel-cell electrodes, battery separators, filters and preforms used to manufacture metal/ceramic composites [1–3]. Copper-based ceramic-metallic (cermet) tapes are used for anodes in solid oxide fuel cells (SOFC) [4]. The synthesis of a porous YSZ matrix is the first step in the fabrication of the cermet. The Cu-YSZ cermet is then prepared by impregnating soluble salts of copper into the porous YSZ structure, after the YSZ has been sintered [4]. As the cermet anode should be 30 vol.% metal to ensure electronic conductivity, and should still remain highly porous to allow diffusion of fuel to the electrolyte interface, very high initial porosity (40 vol.%) is desirable for the YSZ substrate before the addition of soluble salts of copper. The objective of this work was to develop a porous YSZ matrix by tape-casting. A way to produce porosity in the tape is to mix organic particles into the slurry preparation stage [5]. These organic particulates can be chosen so that they pyrolyze during the binder-removal step, leaving stable voids that are not removed during the subsequent sintering procedure [5]. This method of introducing porosity offers a direct control over the porous characteristics of the final ceramic. In addition, it may be possible to form open pore networks because of the potential percolation of these pyrolyzable particles in the green body [5]. Starch is one of the more frequently used pore-forming agents in ceramic technology [6]. Due to its chemical composition (a polysaccharide consisting essentially of C, H and O) this natural biopolymer is easily burnt out during firing without residues in the final ceramic body. It has also been shown that the morphology and the size of the pores are particular to the type of starch used to create the porosity [7]. The tape-casting process for porous ceramics involves the preparation of a concentrated YSZ suspension with the addition www.elsevier.com/locate/ceramint Available online at www.sciencedirect.com Ceramics International 35 (2009) 1783–1791 * Corresponding author. Fax: +54 221 471 0075. E-mail address: palbano@cetmic.unlp.edu.ar (M.P. Albano). 0272-8842/$34.00 # 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2008.10.003