Synthesis of high aspect ratio (K, Na)NbO3 plate-like particles and study on the synthesis mechanism

Abstract

Plate-like NaNbO₃ (NN) templates have been successfully synthesized via a two-step molten salt method using K₂CO₃ as a raw material at 970 °C, which is below the topochemical reaction temperature using Na₂CO₃ as the raw material (higher than 1000 °C). The synthesized plate-like NN particles have a higher aspect ratio with a thickness of 0.5–1 μm, a width of 5–10 μm and a length of 15–25 μm. In this process, we found that Na₂CO₃ or K₂CO₃ plays an important role in removing the (Bi₂O₂)²⁺ layers in the substitution process and the final composition is decided by the type of molten salt. Using KCl as molten salt and Na₂CO₃ or K₂CO₃ as raw material, the (Bi₂O₂)²⁺ layers could be removed by Na₂CO₃ or K₂CO₃ and K⁺ ions can be incorporated into the template during the topochemical reaction and thus (K, Na)NbO₃ (KNN) plate-like particles can be fabricated. The growth process is reasonably elucidated by this growth mechanism.