Topochemical Synthesis of a High‐Aspect‐Ratio Platelet NaNbO₃ Template

Abstract

A high‐aspect‐ratio platelet sodium niobate (NaNbO3) was synthesized by a topochemical reaction. Plate‐like layered‐perovskite Bi2.5Na3.5Nb5O18 (BNN5) as a precursor was first prepared, and then Bi3+ in the precursor phase was replaced by Na+ through topotactic conversion and perovskite NaNbO3 formed at 950°C in NaCl molten salt. NaNbO3 crystals had an average length of 15 μm and a thickness of 0.5 μm. Scanning electron microscope and high‐resolution transmission electron microscope analyses indicated that the retro‐synthesis process of the desired perovskite NaNbO3 retained the morphological and structural features of the BNN5 precursor. It may be possible to synthesize other perovskite‐structured templates using the same method.

Structure Control of NaNbO3Template for Textured Ceramics Synthesized by Two-Step Molten Salt Method

“…The overall molten slat synthesis [12][13] can be viewed as three sequential process: 1) the reactant dissolution; 2) the reactant transport through the melt; 3) the deposition of product onto its existent crystals. In the second MSS course, the BiNNx particles act as insoluble sites for the growth of NaNbO 3 particles.…”

“…In order to prepare textured lead free ceramics of alkali niobates via TGG or RTGG method, appropriate template particles with {0 0 l} crystal planes orientation need to be synthesized. It is reported that platelet perovskite ceramics particles can be synthesized by molten method [11][12][13]. Single-crystal NaNbO 3 particles with {100} facets have been synthesized from BiNN5 by two step molten salt method (or Topochemical synthesis method) [10,11].…”

Synthesis and formation mechanisms of high aspect ratio platelike NaNbO3 particles by topochemical microcrystal conversion

“…Thus, it is crucial synthesizing high aspect ratio template for fabricating textured ceramics. Regarding the synthesis of platelike NaNbO 3 template particles, Saito et al proposed a new technique using topochemical microcrystal conversion (TMC) method [11,12]. This method preserves the morphology of precursor particles (platelike layered-perovskite Bi 2.5 Na 3.5 Nb 5 O 18 (BNN5) particles) and obtains objective compound particles (platelike NaNbO 3 particles), while the chemical composition of the particle is varied by ion exchange and intercalation reactions during TMC process.…”

Synthesis and formation mechanisms of high aspect ratio KNb5Bi2O16 template via topochemical method

“…Saito and Takao successfully synthesized micrometer sized plate-like KNbO 3 from layer-structured K 4 Nb 6 O 17 precursor. Yan et al also synthesized micrometer sized NaNbO 3 from layer-structured Bi 2.5 Na 3.5 Nb 5 O 18 as precursor [6][7][8][9][10]. The synthesis of micronsized KNbO 3 and NaNbO 3 is both via topochemical microcrystal conversion method.…”