Crystal-chemical and physicochemical properties of complex cadmium oxides with pyrochlore and columbite type of structure

Single-phase samples of cadmium pyroniobate and metaniobate were successfully prepared by solid-state synthesis. The crystal structures of cadmium niobates were refined by full-profile fitting of X-ray powder diffraction patterns. The thermal behavior of cadmium niobates in air was studied by thermogravimetric (TG), differential thermal analysis (DTA) and X-ray powder diffraction at elevated temperatures. Found that CdNb2O6 is stable in air up to 1150 °C, Cd2Nb2O7 - up to 1120 °C. Above these temperatures these niobates undergoes a solid state decay with volatilization of cadmium oxide, resulting in formation of metaniobate CdNb2O6 from Cd2Nb2O7, and niobium oxide Nb2O5 from CdNb2O6.