Hydrothermal synthesis and phase stability of CoNb_2O_6 with a rutile structure

摘要

CoNb_2O_6 was prepared by hydrothermal synthesis with polyvinyl alcohol as an additive. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to investigate the lattice parameters and the particle morphology. The products were observed as irregular particles with an average particle size of ca. 500 nm, which agglomerated from thin slices. Compared with the common columbite CoNb_2O_6, which was obtained by a traditional solid-state reaction, the product obtained by the hydrothermal method crystallized into a rutile structure. The rutile CoNb_2O_6 was metastable and it could transform into the columbite structure after calcining at 800 °C in air for 4 h.