A new molten salt synthesis route to the mixed-valence sodium titanate NaTi 2 O 4 has been discovered. Reduction of Na 8 Ti 5 O 14 by Ti metal powder in a 3:1 molar mixture of NaCl:KCl at 770°C produced crystals of NaTi 2 O 4 . Use of the molten salt flux lowered the synthesis temperature of this compound by over 400°C. Time-resolved in situ high-temperature X-ray powder diffraction was used to probe the kinetics and mechanism of the reaction. Energydispersive X-ray diffraction (EDXRD) data revealed that the reaction is rapid; the phase begins to form in 30 min at 770°C, and product formation is essentially complete within 2 h. Crystalline solids are present in the molten salt flux at all times during the course of the reaction, indicating that the mechanism most likely involves reactions occurring at the surfaces of the solid particles, mediated by the molten salt flux. Possible key intermediates identified through EDXRD and quenching studies are Ti 3 O, Na 2 Ti 6 O 13 , and Na 0.54 TiO 2 . This new molten salt synthesis route offers a facile way to reproducibly prepare large samples of this mixed-valence compound for further study.

The design, construction, and use of a furnace from which time-resolved x-ray diffraction data may be measured from reacting mixtures of solids or of solids and liquids is described. The furnace is a vertical tube design, constructed from commercially available components, and can operate at temperatures of up to 1000 °C. The apparatus is designed to heat sample tubes of up to 3 cm diameter. The use of high-intensity synchrotron-generated white-beam x rays allows the tube and its contents to be penetrated; thus x-ray diffraction data can be measured from reactions taking place in laboratory-sized reaction vessels. The energy-dispersive diffraction geometry allows rapid data collection (of the order of seconds); hence reactions can be followed continuously in real time. The use of the furnace is demonstrated by results from experiments performed on Station 16.4 of the Daresbury Synchrotron Radiation Source, UK. Two distinct reaction types are studied, both used to prepare the layered perovskite RbCa2Nb3O10: first, a solid state route at 800 °C and second a flux route, performed in molten RbCl, also at 800 °C.

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 more slowly but is still essentially complete in about 80 min. The in situ EDXRD data also revealed the presence of two or more intermediate phases produced in the solid-state synthesis, corroborated by laboratory quenching studies. Conventional high-temperature diffraction studies of RbCa2Nb3O10 established that no phase changes occur in this material up to 1000 °C.

Niobium Niobium I 5100An Investigation of the Synthesis of the Layered Perovskite RbCa 2 Nb 3 O 10 Using Time-Resolved in situ High-Temperature Powder X-Ray Diffraction. -Time-resolved in situ high-temperature powder XRD reveals that the new molten salt approach, combining a 1:4:3 molar ratio of K 2 CO 3 :CaCO 3 :Nb 2 O 5 with a large excess of RbCl, leads to the rapid formation of the title compound at 800°C. The material crystallizes as soon as the Rb flux melts, and the reaction is complete within a few minutes of reaching 800°C. K 2 CO 3 is a necessary component of the reaction mixture. The solid state reaction of a 1.5:4:3 molar ratio of Rb 2 CO 3 :CaCO 3 :Nb 2 O 5 at 800°C also leads to the formation of the title compound in a relatively short time (80 min). -(GESELBRACHT, M. J.; WALTON, R. I.; COWELL, E. S.; MILLANGE, F.; O'HARE*, D.; Chem.

NaTi2O4. -Crystals of the title compound are prepared by reduction of Na8Ti5O14 by Ti metal powder in a molten NaCl/KCl (3:1) flux at 770°C. The samples are characterized by powder XRD and ED-XRD. The reaction is rapid and the mechanism most likely involves reactions occurring at the surfaces of the solid particles, mediated by the molten salt flux. This new molten salt synthesis route offers a facile way to reproducibly prepare large samples of the title compound. -(GESELBRACHT*, M. J.; NOAILLES, L. D.; NGO, L. T.; PIKUL, J. H.; WALTON, R. I.; COWELL, E. S.; MILLANGE, F.; O'HARE, D.; Chem.