The structure of the lithium ytterbium polyphosphate LiYb(PO3)4 is described. It consists of a three‐dimensional framework made up of spiral (PO3)n chains linked by YbO8 polyhedra. The Li+ cations reside in the tunnels delimited by the framework. The structure is compared with that of some other compounds like LiNd(PO3)4, NaNd(PO3)4, KNd(PO3)4, RbNdP4O12 and Yb(PO3)3.

The lithium terbium polyphosphate LiTb(PO3)4 was prepared by the flux method using a large excess of H3PO4. It was structurally characterized by single‐crystal X‐ray diffraction and found to be isotypic with LiYb(PO3)4. The basic structural units are endless spiral chains, (PO3)n, along the b‐axis direction. The Li+ and Tb3+ cations alternate on twofold axes and are four‐ and eight‐coordinated, respectively. The results of an optical study of this material are also given and discussed.

Lithium holmium(III) polyphosphate(V), LiHo(PO3)4, belongs to the type I of polyphosphates with general formula ALn(PO3)4, where A is a monovalent cation and Ln is a trivalent rare earth cation. In the crystal structure, the polyphosphate chains spread along the b-axis direction, with a repeat period of four tetra­hedra and 21 inter­nal symmetry. The Li and Ho atoms are both located on twofold rotation axes and are surrounded by four and eight O atoms, leading to a distorted tetra­hedral and dodeca­hedral coordination, respectively. The HoO8 polyhedra are isolated from each other, the closest Ho⋯Ho distance being 5.570 (1) Å.

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Key indicatorsSingle-crystal X-ray study T = 293 K Mean '(P±O) = 0.002 A Ê H-atom completeness 51% Disorder in solvent or counterion R factor = 0.024 wR factor = 0.068 Data-to-parameter ratio = 10.5For details of how these key indicators were automatically derived from the article, see