Effect of micro-cracking on the thermal conductivity and thermal expansion of tialite (Al2TiO5) ceramics

The pure and magnesium silicate (Mg2+/Si4+) doped tialite ceramics were prepared from the homogenized mixture of alumina and titania by uniaxial pressing and pressure- less sintering at 1550 degrees C in air. Thermal conductivity and thermal expansion of the doped and undoped tialite ceramics were measured from 30 to 700 degrees C. The identical trend in the behaviour of these thermal properties most probably is influenced by the population, size and shape of microcracks present throughout the grain and grain boundaries as complemented by the microstructural observations. The observed decrease in thermal properties of the doped in comparison to the pure tialite can be attributed to the substitutional Mg2+ and Si4+ at Al3+ site in Al2TiO5 which promotes the phonon scattering and causes modifications in micro-crack density and the morphology of the cracks.