THE CRYSTAL STRUCTURE AND PHASE TRANSITIONS OF β-Zn₂P₂O₇

Abstract

β-Zn 2 P 2 O 7 crystallizes in the C2/m space group with lattice parameters a = 6.61 ± 0.01 Å, b = 8.29 ± 0.01 Å, c = 4.51 ± 0.01 Å, β = 105.4° ± 0.2° and z = 2. The anion, P 2 O 7 −4 , is centered with its mirror plane coinciding with the mirror plane of the space group. The central oxygen atom, however, shows high anisotropic thermal motion and thus it appears that the P—O—P bond angle is linear only as a result of thermal averaging. The cations are found on twofold axes in irregular sixfold coordination and these ZnO 6 groups share three edges with neighboring cations. This cation coordination is, therefore, consistent with that predicted from the red emission of β-Zn 2 P 2 O 7 :Mn ++ .