Influence of Oxygen Activity on the Sintering of MgCr2O4

The sintering behavior of MgCr2O4 powder compacts was investigated as a function of temperature, time, and oxygen activity. The results show that MgCr2O4 cannot be densified to >70% of theoretical density at temperatures up to 1700°C if the oxygen activity exceeds 10−6 atm. The oxygen activity must be decreased to <10−10 atm before densities exceeding 90% of theoretical can be achieved. Weight loss and X-ray data indicated that maximum density occurred at an oxygen activity just above that where MgCr2O4 becomes unstable.