It was known that controlling the alkalinity of the reaction system is the crucial step during the hydrothermal synthesis process of KNb_3O_8. The pure KNb_3O_8 can be synthesized only under the appropriate pH (pH=5-6).

• 其中,调节pH值是关键,只有将pH调节在5-6才能生成纯KNb_3O_8。