Yttrium pyrogermanate, Y2Ge2O7

The structure of diyttrium digermanate, Y2Ge2O7, has been determined in the tetragonal space group P4(3)2(1)2. It contains one Y, one Ge ( both site symmetry 1 on general position 8b) and four O atoms [ one on special position 4a ( site symmetry.. 2) and the remaining three on general positions 8b]. The basic units of the structure are isolated Ge2O7 groups, sharing one common O atom and displaying a Ge - O - Ge angle of 134.9 ( 3) degrees, and infinite helical chains of pentagonal YO7 dipyramids, parallel to the 43 screw axis. The crystal investigated here represents the left- handed form of the tetragonal R2Ge2O7 compounds ( R = Eu3+, Tb3+, Er3+, Tm3+ and Lu3+).