An Investigation of the Synthesis of the Layered Perovskite RbCa2Nb3O10 Using Time-Resolved in Situ High-Temperature Powder X-ray Diffraction

The Dion−Jacobson-type layered perovskite, RbCa2Nb3O10, has been prepared by two different synthetic routes at the moderate temperature of 800 °C. With a new molten salt approach, combining a 1:4:3 molar ratio of K2CO3:CaCO3:Nb2O5 with a large excess of RbCl leads to the rapid formation of RbCa2Nb3O10 at 800 °C. Although the product incorporates rubidium from the molten salt flux, K2CO3 is a necessary component of the reaction mixture. Surprisingly, the solid-state reaction of a 1.5:4:3 molar ratio of Rb2CO3:CaCO3:Nb2O5 at 800 °C also leads to the formation of RbCa2Nb3O10 in a relatively short time. Both of these reactions were studied by time-resolved in situ high-temperature X-ray powder diffraction. Energy-dispersive X-ray diffraction (EDXRD) data confirmed that the synthesis of RbCa2Nb3O10 was accelerated by the molten salt flux; the material crystallizes as soon as the RbCl flux melts, and the reaction is shown to be complete within a few minutes of reaching 800 °C. The solid-state reaction proceeds ...