Synthesis of high-surface area Mn-doped barium hexa-aluminates by a combination of hydrothermal precipitation–calcination route

Abstract

High-surface area (25m2 g−1)Mn-doped barium hexa-aluminates with compositions BaMnAl11O19 and BaMn2Al10O19 were prepared by a combination of hydrothermal precipitation–calcination route. The precursors of the above two compounds were obtained by hydrolyzing a mixture of aqueous solutions of Ba, Al, and Mn at 180 ◦C for 1 h in the presence of urea. The analysis of the hydrothermally prepared samples showed the presence of carbonate and/or hydroxide phases of Ba and Mn and boehmite. Barium mono-aluminate (BaAl2O4), Ba–II-Al2O3, -Al2O3, and a small fraction of MnO2 were observed after calcination of these hydrothermally prepared precursors at 1200 ◦C. A mixture of Ba–I-Al2O3 and Ba–II-Al2O3 phases were found after calcination at 1400 ◦C for 2 h with no other oxide phases of Ba, Al or Mn.