New layered uranium phosphate fluorides: Synthesis, structures, characterizations, and ion-exchange properties of A(UO2)F(HPO4).x[H.sub.2]O (A = [Cs.sup.+], [Rb.sup.+]; X = 0-1)

The synthesis of single crystals of three new layered uranium phosphate fluorides A(U[O.sub.2])F(HP[O.sub.4]).x[H.sub.2]O (A = C[s.sup.+], [Rb.sup.+]; X = 0-1) was carried out by hydrothermal reactions using U[O.sub.3], [H.sub.3]P[O.sub.4], HF, and corresponding alkali metal halides as reagents. The experiments demonstrates that the ion exchange of A(U[O.sub.2]F(HP[O.sub.4])*x[H.sub.2]O materials not only provide a facile route for the low-temperature synthesis of layered alkali-metal uranium phosphate materials but also suggest how the structural diversity of the uranium layered materials could be tuned with different cations.