A new family of lithium rare-earth oxyborates, LiLn6O5(BO3)3 (Ln = Pr-Tm): Crystal structure of the gadolinium phase LiGd6O5(BO3)3

A new family of lithium rare earth oxyborates of formula LiLn6O5(BO3)3 (Ln = Pr-Tm) has been discovered in the ternary-phase diagrams Li2O-Ln2O3-B2O3. Since crystals of LiGd6O5(BO3)3 were grown by the flux method. The structure of the oxyborate was solved using a data collection with a four-circle automatic diffractometer (CAD-4) and with MoKα radiation. The cell is monoclinic (space group P21/c, Z = 4) with a = 8.489(4) angstrom, b = 15.706(3) angstrom, c = 12.117(6) angstrom, β = 132.27(2)degree, and V = 1195(1) angstrom 3. Refinement of 198 parameters using 4402 independent reflections having intensity I > 3σ(I) led to R = 0.037 (wR = 0.087). The structure of LiGd6O5(BO3)3 can be described as a three-dimensional framework, (Gd6O14)10-, of Gd polyhedra connected by common edges and corners, forming cavities where Li and B atoms are inserted. Some oxygen atoms share only Gd polyhedra, justifying the oxyborate label