Synthesis of TaAlO4 compound and Al2O3–TaAlO4 composite ceramic by mechanical alloying and their sintering

This work discusses on the synthesis of TaAlO4 compound and Al2O3–TaAlO4 composite ceramic by mechanical alloying and subsequent sintering from the Al2O3–50 mol%Ta2O5 and Al2O3–5 mol%Ta2O5 powder mixtures, respectively. The samples were milled, compacted and sintered at 1200 °C for 240 min in order to obtain the equilibrium phases. The as-milled powders and sintered samples were characterized by X-ray diffraction, and BET analysis, He-picnometry, and DSC/TG analyses. Only peaks of α-Al2O3 and Ta2O5 were identified in XRD patterns of as-milled Al2O3–5 mol%Ta2O5 and Al2O3–50 mol%Ta2O5 powders. Results have indicated that Al ions were preferentially dissolved into the Ta2O5 lattice in order to form metastable structures. The average density of the Al2O3–5 mol%Ta2O5 and Al2O3–50 mol%Ta2O5 powder particles was reduced during ball milling while that their surface areas were continuously increased during ball milling, respectively. For the Al2O3–50 mol%Ta2O5 powder mixture, the surface area was reduced during the initial milling time. After sintering at 1200 °C for 240 min, the TaAlO4 compound and Al2O3–TaAlO4 composite were formed from the mechanically alloyed Al2O3–5 mol%Ta2O5 and Al2O3–50 mol%Ta2O5 samples, respectively.