Grain size dependence of pure β-eucryptite thermal expansion coefficient

The impact of the grain size, in the range of about ~ 3–12 μm, on spontaneous microcracking and therefore on the value of the bulk β-eucryptite negative thermal expansion coefficient (TEC) has been carefully investigated. In order to control the grain size, pure β-eucryptite powders were synthesized, slip-casted and sintered in air at 1300 °C for 0, 6 and 24 h. The results show that only a slight variation of the intrinsic β-eucryptite TEC is obtained after sintering. On the contrary, the larger the grain size the more important the microcracking phenomenon, leading to a significant and progressive decrease of the bulk β-eucryptite TEC.

► We study the effect of the grain size on the microcracking of pure β-eucryptite. ► Large negative TECs of pure β-eucryptite are mainly related to the microcracking. ► We show for the first time the dependence of β-eucryptite TEC with the grain size. ► Misconception of supposing β-eucryptite as a highly NTE material is cleared. ► An empirical linear relationship between TECs and the mean grain size was proposed.