Joining green ceramic tapes made from water-based slurries by applying low pressures at ambient temperature

Abstract

The production of multilayer ceramics by laminating stacked green ceramic tapes is one of the most attractive methods to fabricate layered materials. In general, organic additives are employed which implies high pressures (up to 130 MPa) and temperatures (up to 110 °C) to originate mass flow between stacked green ceramic tapes which is time and energy consuming. The complete elimination of the residues before sintering of the bodies involves environmental unfriendly emissions, while expensive raw materials are just burned out and, in general, the sintered materials present rather high porosity levels. In this work, a lamination technique for joining ceramic green tapes fabricated from aqueous ceramic slurries is investigated. As a first approach to the problem, the feasibility of obtaining monolith samples made of six tapes of the same composition (95 vol.% Al 2O 3–5 vol.% YTZP) was investigated to establish the optimum conditions to obtain defect-free sintered materials. The cross-section of sintered pieces was investigated for large defects and for delaminations using dye-penetrating techniques; polished cross-sections of the samples that did not show any cracking at this observation level were further analysed by optical and scanning electron microscopy. Results were correlated with the engineering stress–apparent strain curves recorded during pressing and with the green density values. The control of the stress–strain curves during the pressing process was demonstrated as an adequate means to optimise the lamination parameters.