Effect of Oxygen Concentration and Tantalum Addition on the Formation of High Temperature Bismuth Oxide Phase by Mechanochemical Reaction

High-temperature face-centered cubic bismuth oxide phase is a material of great interest given its unique properties. In the present study, α-Bi(2)O(3) and tantalum powders were used as the starting powders for the formation of high-temperature bismuth oxide phase via mechanochemical synthesis by high energy ball milling. (Bi(2)O(3))(80)(Ta)(20) and (Bi(2)O(3))(95)(Ta)(5) in weight concentrations were milled in either an oxygen-free argon-filled glove box environment or an ambient atmosphere to investigate the effects of oxygen concentration and tantalum addition. The as-milled powders were examined using X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, and differential scanning calorimetry to reveal the structural evolution. The experimental results showed that for (Bi(2)O(3))(95)(Ta)(5) powder mixtures milled within the glove box, tantalum gradually reacted with the α-Bi(2)O(3) phase and formed a β-Bi(7.8)Ta(0.2)O(12.2) phase. For (Bi(2)O(3))(80)(Ta)(20) milled under the same conditions, Ta and α-Bi(2)O(3) mechanochemically reacted to form δ-Bi(3)TaO(7) and bismuth after 10 min of high energy ball milling, whereas milling (Bi(2)O(3))(80)(Ta)(20) under the ambient atmosphere with a much higher oxygen concentration accelerated the mechanochemical reaction to less than five minutes of milling and resulted in the formation of high-temperature δ-Bi(3)TaO(7) phase.