Domain structure in the polar phase of ammonium rochelle salt

Abstract

X-ray studies on ammonium Rochelle salt have been made at 103K and 293K by Weissenberg photographic method with imaging-plate. We observed split Bragg reflections at 103K using cylindrical single crystals of which axes are parallel to a and b. The split Bragg reflections can be explained by occurrence of domain structures. The domains are associated with the phase transition from the orthorhombic P2₁2₁2 phase to the monoclinic P12₁1 phase. The monoclinic angle β is estimated to be 91.2°. The superlattice reflections are also observed on reciprocal lattice points (h ± ½ k l). No incommensurate satellite reflection is observed.