Effect of Microcracking on the Thermal Diffusivity of Fe 2 TiO 5

The effect of microcracking on the thermal diffusivity of polycrystalline Fe 2 TiO 5 subjected to a range of annealing treatments was investigated. At fine grain size (∼1 μm), the thermal diffusivity exhibited the decrease with increasing temperature common for dielectrics. Extensive microcracking in the larger‐grain‐sized materials significantly decreased their thermal diffusivity. On heating, the microcracked materials exhibited increased thermal diffusivity at elevated temperatures which can be attributed primarily to microcrack closure and healing; on cooling, they exhibited a pronounced hysteresis, attributable to irreversible crack opening and closing. Thermal cycling closed the hysteresis curves, which suggests permanent changes in microcrack morphology. It appears that microcracking is a promising technique for tailoring ceramic materials to a combination of high thermal shock resistance and good insulating capability.