High-Pressure B-Type Polymorphs of Some Rare-Earth Sesquioxides.

New high pressure forms of the sesquioxides of holminum, erbium, thulium, ytterbium, lutetium, and yttrium have been obtained by exposure of the C-type sesquioxides to pressures between 25 and 40 kilobars and temperatures between 900 degrees and 1020 degrees C. X-ray diffraction analysis shows that these new high-pressure phases are of the monoclinic B-type which is known for several of the lighter rare-earth sesquioxides (samarium through dysprosium).