Simultaneous fabrication of a composite with low thermal expansion and high strength in the eucryptite — yttria-stabilized PSZ system

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

“…This statement may seem in contradiction with some previous studies that have already reported zero thermal expansion in ␤-eucryptite-based oxide composites. 33,35 Nonetheless, those composites exhibited no full-densification and micro-cracking that probably contributed to the relaxation of stresses applied onto the ␤-eucryptite and to the enhancement of its extrinsic negative CTE. 30 In the current work, we mainly attribute the observed intrinsic ␤-eucryptite CTE decrease to the large compressive residual thermal stresses that should be generated on ␤-eucryptite grains during cooling.…”

“…33 In effect, the use of 16 mol% of ceria instead of 3 mol% of yttria as stabilizing agent increases the tetragonal phase stability in ZE composites. As a result, a linear thermal expansion behaviour was obtained overall the studied temperature range.…”

“…12,[27][28][29] Such highly negative values indicate the occurrence of spontaneous micro-cracking due to the ␤-eucryptite thermal expansion anisotropy. 30 The strategy of combining ␤-eucryptite and an oxide like alumina 31,32 or zirconia 33,34 to prepare a near zero CTE material has been already reported. For example, ␤-eucryptite-3 mol% yttria partially stabilized zirconia (3YPSZ) composites (55 wt.% ␤-eucryptite/3YPSZ and 65 wt.% ␤-eucryptite/3YPSZ) processed by slip-casting and conventional sintering (T < 1325 • C) exhibit a very low CTE (1.45 × 10 −6 / • C and −0.52 × 10 −6 / • C respectively) and a relative high bending strength (220 MPa for 55 wt.% ␤-eucryptite/3YPSZ).…”

“…However, neither the characterization of ␤-eucryptite-zirconia interaction nor the final composite density have been studied. 33 The addition of ␤-eucryptite glass-ceramic powders in alumina also influences its thermal expansion behaviour. 35 Composites with the composition 45 wt.% ␤-eucryptite-Al 2 O 3 show a CTE of 4.36 × 10 −6 / • C that is explained in terms of ␤-eucryptite-alumina interactions and micro-cracking development, once more without given more details on the nature of this interaction and/or microstructural aspects.…”

High Thermal Shock Resistant Aluminium Titanate Type Ceramics

“…On the other hand, the highly anisotropic materials like Al 2 TiO 5 , showing grain boundary microcracking in polycrystalline bodies have extremely low strength [6]. The strength can be improved by alloying with a material of high strength while the matrix maintains the low thermal expansion [7,8]. The aim of this work was to improve the mechanical characteristics of aluminium titanate ceramics, synthesised from equimolar amount of Al 2 O 3 (corundum) and of TiO 2 (anatase), by alloying with 5% and 10% (by weight) stabilised zirconia.…”