Low-temperature solid reaction synthesis of high sinterability MgAl₂O₄ powder from -Al₂O₃+MgO and /-Al₂O₃+MgO batches

By using nanometric gamma-Al2O3+MgO and theta/alpha-Al2O3+MgO mixtures, two kinds of pure nanometric MgAl2O4 (MAS) powders were successfully synthesized in air at 1250 ? and 1200 ? for 60 min, respectively. The phase transformation and morphology evolution during heating of gamma-Al2O3+MgO showed two MAS formation paths, i. e., gamma/theta-Al2O3+MgO -> MAS and alpha-Al2O3+MgO -> MAS. As a result, the pure MAS powder synthesized by gamma-Al2O3+MgO exhibited a bimodal aggregated particle size distribution. Correspondingly, the MAS powder from theta/alpha-Al2O3+MgO presented a unimodal aggregated particle size distribution. Further sintering experiments showed that the bimodal MAS powder prepared by gamma-Al2O3+MgO had high sinterability as it can be consolidated to high relative density ceramics (99.80%) at low temperature (1450 ?) for short dwelling duration (120 min) in air. Moreover, its sintered MAS ceramics also showed transparency in infrared range with the maximum transmittance of 63.8%. The excellent sinterability of the bimodal MAS powder indicates that the proposed MAS synthesis method by using nanometric gamma-Al2O3+MgO is helpful to fabricate MAS ceramics of high density.