A new high-pressure form of Ka1Si 3 O 8 under lower mantle conditions

In situ X-ray diffraction measurements have been made on KAlSi3O8 hollandite using diamond anvil cell and multianvil apparatus combined with synchrotron radiation. Both of the measurements with different techniques demonstrated that K-hollandite transforms to a new high-pressure phase (hollandite II) at ∼22 GPa upon increasing pressure at room temperature. The X-ray diffraction peaks of the new phase were reasonably indexed on the basis of a monoclinic cell with I2/m space group. Hollandite II was also confirmed to be formed at high temperatures to 1200°C and pressures to 35 GPa, which was que... Mehr ...