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Comparison of the isotypic solid-state structures of disodium zinc diphosphate (Na2ZnP2OT) and disodium zinc diphosphate doped with europium (Nal.94Euo.02ZnP207) shows the europium to share a sodium site and to exist at the intersection of two mirror planes in the layer-like structure. The emission characteristics of this rare-earth-containing material are reported. CommentIn the interest of understanding the influence of crystallographic symmetry elements upon the emission of Eu m in an oxide environment, we have prepared Na2ZnP207, (I), and Na2ZnP207 doped with Eu m, (II) (refined formula: Nal.94Eu0.o2ZnP2OT).The doped crystal glows red under excitation with 287 nm radiation, whereas the undoped crystal displays no emission. Both samples crystallize in the tetragonal space group P42/mnm and refinement shows the two forms to be isotypic.The structure of Na2ZnP20: may be compared with the structures of members of the family A2[BHP2OT. Gabelica-Robert (1981) has reported that compounds of this family, with A = Na and B = Zn or Co, are isotypic and are found in a tetragonal form (a = 7.6 and c = 10.2 ,~). We have previously reported the structures of two different forms of Na2CoP207 (triclinic and orthorhombic space groups; Erragh et al., 1991), distinguished by their differing colors which reflect the presence of octahedral (rose) or tetrahedral (blue) cobalt coordination. The blue form is a layer structure with

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