Early Transition Metal Oxides and a Pinch of Salt: New Synthetic Routes to Titanates and Niobates

Abstract

Molten salts have traditionally been used as recrystallizing solvents for the crystal growth of mixed metal oxides. In recent years, many examples of the direct preparation of mixed metal oxides from molten salt solutions have been reported. We have been exploring the use of chloride melts as a reaction media to prepare complex early transition metal oxides. Specific examples of new synthetic routes to interesting titanates and niobates will be presented. In one case, we have prepared a series of layered niobate perovskite solid acids from molten salts at temperatures well below those traditionally used in solid state syntheses. In the second case, we have discovered a new synthetic route to a poorly characterized reduced calcium titanate that is otherwise very difficult to make. The synthesis and characterization of these two classes of compounds will be described.

Rapid Topochemical Modification of Layered Perovskites via Microwave Reactions

“…RbLaNb 2 O 7 , KCa 2 Nb 3 O 10 , Li 2 CaTa 2 O 7 , and Na 2 La 2 Ti 3 O 10 were synthesized from the corresponding oxides and carbonates by methods similar to previously reported solid state reactions. − All ceramic reactions were done in alumina crucibles in air. RbLaNb 2 O 7 was synthesized by mixing Rb 2 CO 3 , La 2 O 3 , and Nb 2 O 5 in a molar ratio of 1.3:1:2, respectively.…”

“…The ground mixture was preheated at 850 °C for 12 h, reground, and then heated at 1050 °C (24 h) and 1100 °C (24 h) with one intermediate grinding. KCa 2 Nb 3 O 10 was prepared by a method similar to the molten salt synthesis reported by Geselbracht et al K 2 CO 3 , CaCO 3 , Nb 2 O 5 , and KCl were mixed in a 1:4:3:15 molar ratio, respectively. The mixture was ground and heated at 900 °C (24 h), 950 °C (12 h) and 1000 °C (2 h).…”