Improved crack resistance and thermal conductivity of cubic zirconia containing graphene nanoplatelets

•8YSZ/GNP composites show strong rising R-curve for cracks facing the GNP planes.•They are highly tolerant due to the appropriate combination of elastic modulus and toughness.•Anisotropy in thermal expansion allow matching between components to limit residual strains.•Enhanced and anisotropic thermal conduction aid heat transfer in specific directions.•Charge transfer between GNP and 8YSZ is proposed to explain the thermal conductivity. Composites of 8 mol.% yttria-stabilized zirconia (8YSZ) with graphene nanoplatelets (GNP) have been pointed as alternative interconnectors in SOFC due to their mixed ionic-electronic conduction. Here we show that GNP addition provides rising crack-resistance behavior, with long crack toughness up to 78% higher than that of 8YSZ, also improving its thermal conductivity (up to 6 times for the in-plane direction). Toughness versus crack length is measured for 7 and 11 vol.% of GNP using single edge V-notched beam technique and ultrashort pulsed laser notching; and thermal behavior is analyzed by the laser flash method. Materials also have highly anisotropic coefficient of thermal expansion. These properties contribute to enhance their performance under the harsh operating conditions of SOFC, as thermal residual stresses could be reduced while significantly improving the system mechanical stability. Moreover, the heat transfer may be enhanced especially along the interface direction which would increase the system efficiency.