An alternative solid-state method to prepare pyrochlore-free KTaO3 at low temperature

Perovskite-type KTaO3 powder was synthesized by an alternative solid-state method at low temperature. Stoichiometric ammonium tantalum hydroxide, K2C2O4 and KF were mixed in water and then dried at room temperature. The crude product was formed by calcining the dried mixture at different temperatures. Pyrochlore-free KTaO3 powder was successfully synthesized after treating the crude product with water. KF plays an important role to inhibit the formation of pyrochlore K2Ta2O6 during the calcination process of ammonium tantalum hydroxide/K2C2O4/KF mixture. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, UV–vis diffuse reflectance (UV–vis) spectroscopy and thermogravimetric (TG) analysis were used to characterize the precursor compound and as-prepared samples. XRD results show that pyrochlore-free KTaO3 powder can be obtained at 600 °C. SEM results reveal that the as-prepared products are agglomerated and each of the agglomerations consists of many small grains with 10–30 nm in diameter.

Pyrochlore-free KTaO3 powder was prepared at 600 °C using tantalum hydroxide/K2C2O4/KF raw materials. Pyrochlore K2Ta2O6 and perovskite KTaO3 coexist at 600 °C using tantalum hydroxide/K2C2O4 raw materials.Figure optionsDownload as PowerPoint slideHighlights
► In-situ degradation of TaOx(OH)5−x(NH4)x, K2C2O4 and KF promotes the reaction.
► Synthesis of KTaO3 displayed a two-step reaction path with the intermediate formation of K2TaO3F.
► Formation of intermediate K2TaO3F benefits to prepare pyrochlore-free KTaO3 at low temperature.
► Pyrochlore-free KTaO3 is prepared at 600 °C, which is the lowest temperature reported so far by hard chemistry method.
► Synthetic method is a facile, rapid, low price and environment friendly route.