Surface relief induced by martensitic transformation in phosphorus-bearingdicalcium silicate

Crystals of (Ca(1.955)square(0.045))(Si0.91P0.09)O-4, where square denotes a vacancy, have been prepared and examined by XRD, optical microscopy, SEM, and AFM. At 20 degrees C, the crystals are composed of 38% alpha(L)' and 6 2% beta phases, Upon cooling to -185 degrees C, the alpha(L)'- to beta-phas e transformation occurs, which increases the P-phase composition to 72%. Th e transformation is also accompanied by the formation of platelike surface reliefs, The surface relief angles have been determined from observations ( 7.9 degrees +/- 0.2 degrees) and calculations based on a phenomenological a nalysis (7.83 degrees), The fair agreement of these values indicates that t he transformation is martensitic and mainly governed by a shear mechanism.