Reducing the sintering temperature for MgO-Al2O3 mixtures by addition of cryolite (Na3AlF6)

[[abstract]]The preparation of near stoichiometric spinet and alumina-rich spinet composites from Al2O3, and MgO powders with the addition of Na(3)AIF(6) up to 4 wt% in the temperature range 700degrees-1600degreesC was studied; 98 wt% spinet containing 72 wt% Al2O3, can be produced from the mixture of 72 wt% (50 at.%) Al-2O3 + 28 wt% (50 at.%) MgO powders with the addition of 1 wt% Na(3)AIF(6) fired at 1300degreesC for 1 h. Spinels containing 81-85 wt% Al2O3 can be produced from either the mixture of 90 wt% (78 at.%) Al2O3 + 10 wt% (22 at.%) MgO or the mixture of 95 wt% (88 at.%) Al2O3 + 5 Wt% (12 at.%) MgO powders with the addition of 4 wt% Na(3)AIF(6) in the temperature range 1300degrees-1600degreesC by using a torch-flame firing for 3 min, followed by quenching in water, while the same system under slow cooling in a furnace results in spinet containing 74-76 wt% Al2O3. Microscopic studies indicate that the alumina-rich spinet composites consist of a continuous majority spinel phase and an isolated minority corundum phase, regardless of slow cooling in a furnace or quenching in water.[[fileno]]2020305010049[[department]]材料