Thermal expansion of β-eucryptite in oxide-based ceramic composites

This paper presents an experimental investigation on the thermal expansion behaviour of β-eucryptite (E) when it is used for processing alumina/β-eucryptite (AE) or zirconia/β-eucryptite (ZE) composites. Composite materials were prepared from a β-eucryptite powder synthetised in our laboratory and commercially available alumina or zirconia nanopowders. In order to preserve the β-eucryptite crystalline phase in sintered materials, the pressureless sintered step was performed at relatively low temperatures (<1300 °C). It is experimentally shown that in well-densified oxide-based composites, the β-eucryptite lost its slightly negative thermal expansion coefficient. This behaviour could be related to compressive residual stresses applied on β-eucryptite grains due to the thermal expansion mismatch between alumina or zirconia and the β-eucryptite.