Boysen, Hans; Frey, Friedrich; Schrader, H.; Eckold, G.
On the proto- to ortho-/clino enstatite phase transformation: Single crystal X-ray and inelastic neutron investigation.
In: Physics and Chemistry of Minerals, Vol. 17, Nr. 7: S. 629-635
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High temperature X-ray investigations of enstatite from Bamble shows that the proto (PE) to ortho (OE)/clino (CE) inversion is most probably triggered by preformed single stacking faults acting as nuclei and completed by a subsequent rapid growth process compatible with the martensitic nature of the transformation. New stacking faults are created during the transformation. From a detailed analysis of line profiles we deduce the formation of \"out-of-phase\" OE domains which are intergrown with well ordered CE sequences. Single layer faults and PE type faults can be ruled out. A transformation mechanism similar to that proposed by Sadanaga et al. (1969) fits well with our results. Inelastic neutron scattering experiments show that the origin of the transformation is not an elastic shear instability. A transient increase of the elastic constant c55 is interpreted as a secondary effect caused by elastic strains in the progress of the transformation.