Synthesis and sintering at low temperature of a new nanostructured beta-Eucryptite dense compact by spark plasma sintering

The solid state reaction between kaolin and Li₂CO₃ with a 1:1 M composition has been studied in the temperature range 380°C-550 °C. The role played by Li₂CO₃ (basic medium) in the thermal transformation of the kaolin has been investigated by X-Ray diffraction, FESEM, TEM, MAS-NMR and XPS techniques. For the first time, a nanostructured high density β- Eucryptite (<10 nm) has been obtained by Spark Plasma Sintering (SPS) at 550 °C in high vacuum. The atmosphere used in sintering treatments has a determinant role in lithium migration and crystallization of β- Eucryptite. In the case of low vacuum treatments, an amorphous LiAlSiO₄ geopolymer type material was obtained. Due to exclusive properties and performances of β- Eucryptite based materials, the results reported in the present investigation open new perspectives for new nanostructured and amorphous functional materials with null thermal expansion, ionic conduction and remarkable mechanical properties.