Figure 4.

SEM images of Na7(H3O)Nb6O19·14H2O precursor prepared at different NaOH concentrations: a, b 0.5–0.8 M, and c, d 1–1.5 M.

Wu and Xue Nanoscale Res Lett 2011 6:14   doi:10.1007/s11671-010-9757-0