Effect of excess Nb₂O₅ on the growth behavior of KSr₂Nb₅O₁₅ particles by molten salt synthesis

The single-step and two-step molten salt synthesis (MSS) methods have been utilized to synthesize anisometric KSr₂Nb₅O₁₅ (KSN) particles. To facilitate morphological and dimensional control, the effects of excess Nb₂O₅ on the growth behavior of the product particles have been investigated, and a defect reaction growth mechanism is proposed. It was found that excess Nb₂O₅ could promote the growth of product particles in both the single-step and two-step MSS. The aspect ratio of the product particles increased and reached the maximum value (16.85 for the single-step MSS and 52.29 for the two-step MSS), then decreased with increasing amounts of excess Nb₂O₅. Using single-step MSS, two morphologies (rod-like and columnar) were formed as the excess Nb₂O₅ content was changed. This was caused by the nucleation of new particles at the particle edges. However, needle-like KSN particles were observed in the two-step MSS, which can be explained by the defect reaction mechanism. The in situ epitaxial growth, as controlled by the defect reaction mechanism, determines the morphology and size of the particles obtained using the two-step MSS.