Molten salt synthesis of zinc aluminate powder

ZnAl2O4 powder was synthesised by reacting equimolar ZnO and Al2O3 powders in alkaline chlorides (LiCl, NaCl or KCl). Formation of ZnAl2O4 started at about 700 °C in LiCl and 800 °C in NaCl and KCl. With increasing temperature, the amounts of ZnAl2O4 in the resultant powders increased with a concomitant decrease of ZnO and Al2O3. ZnAl2O4 powder was obtained by water-washing the samples heated for 3 h at 1000 °C (LiCl) or 1050 °C (NaCl and KCl). ZnAl2O4 formed in situ on Al2O3 grains from the surface inwards. The synthesised ZnAl2O4 grains retained the size and morphology of the original Al2O3 powders, indicating that a template formation mechanism dominated formation of ZnAl2O4 by molten salt synthesis.