Shape-Preserving Reactive Conversion of Hollow K2Nb2O6 Precursor into KTiNbO5 Architectures

We have demonstrated a hydrothermal route to crystallize K2Nb2O6 hollow spheres composed of primary and uniform single crystalline nanoplates by Ostwald ripening growth mechanism. By elaborating a coating scheme with Ti metal powder precursor in KOH aqueous solution under hydrothermal conditions, followed by a calcination procedure, we fabricated a kind of novel KTiNbO5 spherical architecture which well inherited the hollow motif of K2Nb2O6 precursor. The thin nano-sized spines on the surface of KTiNbO5 spheres can withstand the stress caused by the crystallization and sintering at 660 degrees C for 3 h. However, the original shell structures are seriously destroyed at 700 degrees C for 2 h. The structural transformation is well reflected by the shift of UV-Vis absorption spectra during the thermal-induced solid-state phase conversion process. The present work makes a progress to readily and mildly synthesize niobates, and presents a heuristic guideline for the rational design of other Nb-based functional materials.