Synthesis of the new layered oxides NaRbLnMO5 (Ln = La, Nd, Sm, Eu, Gd; M = Nb, Ta)

The new layered transition metal oxides NaRbLnMO5 (Ln = Nd, Sm, Eu, Gd; M = Nb, Ta) were synthesized by direct solid-state reaction. NaRbLaNbO5 crystallizes with a tetragonal unit cell [a=5.839(6) Å, c=8.313(1) Å] analogous to that of the related compound NaKLaNbO5, while NaRbLaTaO5 indexes to a larger monoclinic unit cell [a=9.577(2) Å, b=5.834(1) Å, c=8.323(2) Å, β=93.00(2)]. NaRbLnNbO5 can be prepared for Ln = Nd, Sm, Eu, Gd, and NaRbLnTaO5 can be prepared for Ln = Nd, Sm. Both series of compounds show the expected decrease in unit cell volume as the size of the lanthanide decreases. NaRbLaNbO5 is also amenable to ion exchange, forming Li2−xRbxLaNbO5 upon reaction with molten lithium nitrate.