High-pressure synthesis of the new rare-earth oxoborate beta-Gd2B4O9.

beta-Digadolinium tetraborate (beta-Gd2B4O9) was synthesized under high-pressure/high-temperature conditions in a Walker-type multi-anvil apparatus at 3 GPa and 1223 K from the pure binary oxides. Its crystal structure has been determined from single-crystal X-ray diffraction data collected at room temperature. The compound is isotypic with the known compound beta-Dy2B4O9, which was synthesized under extreme conditions by use of a flux.