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Abstract: 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. [Copyright &y& Elsevier]

Abstract: Well-developed acicular NaSr2Nb5O15 (NSN) particles were successfully synthesized by a simple ion-exchange approach based on a molten salt synthesis method. The crystal structure and morphologies of the particles were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, and selected area electron diffraction. The results indicated that uniform acicular NSN particles with large aspect ratio could be obtained by heating of a mixture with a weight ratio of salt-to-mixture of 5:1 for 4h at 1200°C. The acicular NaSr2Nb5O15 particle that is formed by the penetration of sodium ions (Na+) into the crystal lattice of KSr2Nb5O15 to replace potassium ions (K+) is single crystalline and the growth direction of the particle is determined to be the <001> crystallography direction. [Copyright &y& Elsevier]