Abstract
MgSiO3 perovskite is believed to be a dominant constituent of the Earth’s lower mantle. Experimental results on the effect of Al on the compressibility of MgSiO3 perovskite have been pretty controversial. Two kinds of the Al substitution mechanisms are expected: 2Al = Mg + S and 2Al = 2Si + (as a vacancy site) O [1]. Theory predicts that the latter mechanism significantly increases the compressibility [2]. Recently, Kojitani et al (2005) demonstrated the structural differences between these two types of Al-bearing MgSiO3 perovskite on the basis of Rietveld analyses. In this work, the volume compression measurements were performed on the oxygen vacancy type Al-MgSiO3 perovskite by using synchrotron radiation x-rays. Data were collected under hydrostatic conditions using helium pressure transmitting medium. Preliminary results show that the isothermal bulk modulus is reduced due to the incorporation of Al2O3 in perovskite with oxygen vacancy.
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More From: Acta Crystallographica Section A Foundations of Crystallography
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