In recent years, much progress has been made in the production and evaluation of ceramic sensors for the on-line testing of the aluminium composition before casting. However, the use of these sensors in such applications is often limited by their poor thermal shock resistance. The purpose of this paper is to communicate the initial findings of research aimed at improving the thermal shock resistance of beta-Al2O3 ceramic used for the detection of sodium in aluminium. In order to improve the thermal shock resistance of beta-Al2O3, Al2O3 and ZrO2 fibres have been incorporated into beta-Al2O3. Other second phase materials including Al2TiO5 and SiC in a beta-Al2O3 matrix have been tested, but their chemical stabilities during sintering are poor. WC is stable in a beta-Al2O3 matrix if it is pressure-sintered in argon.