REVISED STRUCTURE OF THE ORTHOBORATE YBO3

The YBO3 orthoborate was prepared by a flux evaporation process and th e diffraction lines of its X-ray pattern were indexed on the basis of single crystal data. Crystal structure was determined (R=0.035) in the P6(3)/m space group from data recorded on a four-circle automatic dif fractometer, with cell parameters a=3.776 (1) Angstrom, c=8.806 (4) An gstrom. The structure consists of a three-dimensional network made up of eightfold coordinated yttrium atoms and fourfold coordinated boron atoms. The structure exhibits two nonequivalent environments for the y ttrium ions, which is confirmed by luminescence studies using the Eu3 ion as structural probe. This work was completed by B-11 NMR and IR s tudies, which show that boron has tetrahedral coordination. (C) 1997 A cademic Press.