Preparation of hydrated rubidium molybdenum bronze from hydrated sodium molybdenum bronze by ion exchange, and its characterization and thermal decomposition

Abstract

A new type of hydrated rubidium molybdenum bronze has been synthesized, which was very unstable. It gave a orthorhombic structure with lattice constantsa=3.74(1), b=22.82(7), and c=3.85(1) Å. Exchange of Na⁺ ion with Rb⁺ ion took place within 30 s. The exchange reaction, [Na⁺(H₂O)_n]_x[MoO₃^x–]+Rb⁺ ⇆[Rb⁺(H₂O)_n]_x[MoO₃^x–]+Na⁺ , took place in both directions by changing the Na⁺/Rb⁺ ratio in the mixed solution. A concentration of about 0.05 mol Na in the sample was the minimum value necessary to retain the structure of hydrated sodium molybdenum bronze. We obtained the blue rubidium bronze, Rb_0.30MoO₃ , by heating hydrated rubidium bronze in nitrogen. This is a new route to producing the metal bronze at low temperature. We also obtained rubidium decamolybdate by heating it in air. This is also a new method for producing rubidium decamolybdate by solid-state reaction.