Complicated effects of aluminum on the compressibility of silicate perovskite

The effect of alumina content on the compressibility of MgSiO3 perovskite was studied using both diamond-anvil and multi-anvil techniques. Hydrostatic compressions were performed on MgSiO3 perovskites using helium as a pressure-transmitting medium up to 33 GPa. Dissolution of up to 10 mol% Al2O3 clearly makes perovskite more compressible, and this effect was apparent even when only 1% Al2O3 was dissolved. On the other hand, no meaningful effect was observed when the measurement was made using the multi-anvil apparatus. Various results reported so far have shown widely scattered values, and it is difficult to explain this range of results. It is likely that one or more unknown parameters exist that have not yet been accounted for during experimentation. Further careful studies are required to provide an answer this question, which is important to a clear understanding of the lower mantle.