DOMAIN-STRUCTURE IN THE POLAR PHASE OF AMMONIUM ROCHELLE SALT

X-ray studies on ammonium Rochelle salt have been made at 103K and 293 K by Weissenberg photographic method with imaging-plate, We observed s plit Bragg reflections at 103K using cylindrical single crystals of wh ich axes are parallel to a and b, The split Bragg reflections can be e xplained by occurrence of domain structures. The domains are associate d with the phase transition from the orthorhombic P2(1)2(1)2 phase to the monoclinic P12(1)1 phase, The monoclinic angle beta is estimated t o be 91.2 degrees. The superlattice reflections are also observed on r eciprocal lattice points (h +/- 1/2 k l). No incommensurate satellite reflection is observed.