Sodium terbium(III) polyphosphate.

Single crystals of the title compound, NaTb(PO(3))(4), were obtained by solid-state reaction. This compound belongs to type II of long-chain polyphosphates with the general formula A(I)B(III)(PO(3))(4). It is isotypic with the NaNd(PO(3))(4) and NaEr(PO(3))(4) homologues. The crystal structure is built up of infinite crenelated chains of corner-sharing PO(4) tetra-hedra with a repeating unit of four tetra-hedra. These chains, extending parallel to [100], are linked by isolated TbO(8) square anti-prisms, forming a three-dimensional framework. The Na(+) ions are located in channels running along [010] and are surrounded by six oxygen atoms in a distorted octa-hedral environment within a cut-off distance <2.9 Å.