Mechano-Thermal Synthesis and Characterization of BaMnO3 Nano-Needles

Various BaMnO3 samples were prepared by planetary ball milling technique by varying the milling time from 1 to 20 h at a speed of 350 rpm, and all the milled powders were subsequently annealed at 1000 °C for 16 h in order to improve the phase formation and purity. While the ball milled powders are amorphous in nature, the annealed materials reveal nanocrystalline hexagonal perovskite structure with space group, P6(3)/mmc (194). The 15 h ball milled and subsequently annealed material shows lattice parameters, a = 0.5704(5) and c = 0.4801(6) nm with lowest average crystalline size of ~18 nm. It is found that, as the milling time increases (from 1 h to 15 h) the average crystalline size decreases slightly from 25.7 nm to 18.1 nm. The nano rod/needle shaped particles with the size of ~97 nm are observed through SEM images for the BaMnO3 phase. Interestingly, the present BaMnO3 nanopowder reveals photo-luminescent property under the excitation wavelengths of 270 and 350 nm. The nanocrystalline BaMnO3 powder exhibits higher reflectance, which finds application in NIR reflective pigments.