Upcycling spodumene tailings in the preparation of high alumina porcelain composition sintered at 1200––1400 ˚C

Concentration of spodumene from lithium pegmatite ore generates large amounts of tailings that need to be recycled for sustainability and circular economy concerns. This study investigated the preparation of high-alumina porcelain compositions incorporating spodumene tailings, i.e., quartz feldspar silt (QFS). The mix design closely matched the theoretical composition of 60.51-wt.% Al₂O₃, 34.34-wt.% SiO₂, 2.98-wt.% K₂O, 0.66-wt.% Na₂O, and 0.33-wt.% CaO. For comparison, a reference composition free of QFS, composed of commercial materials, was also prepared. Both compositions were thermally treated at 1200℃, 1300℃, and 1400℃. The prepared samples were characterised using several techniques, including X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray spectroscopy, thermogravimetry/differential scanning calorimetry, compressive and flexural strength tests, water absorption, apparent density, and dilatometry at high temperatures up to 1400℃. The results show that corundum and mullite are the primary crystalline phases formed at high temperatures in addition to an amorphous glassy phase. The compressive and flexural strengths were 25–60 and 6–10 MPa, respectively. QFS milling favoured phase densification, resulting in greater sintering shrinkage. However, all samples were relatively stabilised after the first heating cycle and exhibited less than 1% dimensional changes during the second heating cycle at 1400℃. The reference and 26.4-wt.% QFS samples exhibited comparable results, indicating the potential for upcycling spodumene tailings as feldspar substitutes in the development of corundum-mullite based-ceramics for possible high temperature applications.