Light Refraction at the Interface between Coexisting Phases of KHCO_3

概要

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Polarizing naicroscope observations of ferr'oelastic donaains which coexist with the nuonoclinicphase in as-grown KHCO3 crystals below T. -' 318 K are reported. The natttre as well as theorientation of the phase boundary are predicted in the franae of the theory of Domain-wallorientations in ferroelastics assttming that the domains are triclinic. Specific light refractionexperitaaents at this interface are carried on and analytical expressions betxveen the angles ofincidence and of refraction are established using crystal optics. Frona tneastureunents ol' theseangles, the orientation of' the phase botrndary is derived with a precision of about 0.2 degree. Theexcellent agreement between this orientation and the one predicted f'rotau the lattice parametersof the two phases shows that the bovrndary corresponds to a ferroelastic Domain-wall of theW'-type and that the observed domains well consist of a triclinic phase.
1998-04-15