Development of a Low-Temperature X-ray Diffractometer with a Weissenberg Camera utilizing an Image Plate

A new type of X-ray apparatus with an image plate as an area detector has been developed in order to study phase transitions at low temperatures. The system is essentially composed of a high-precision-type double-axis diffractometer with a vertical-type Weissenberg camera controlled by a computer and is combined with a helium-gas closed-cycle cryogenic refrigerator. Oscillation and Weissenberg photographs down to 12 K were taken with an image plate. The image plate is replaced easily by a conventional scintillation counter, so that both photographic and counter methods are available. New superlattice reflections associated with the phase transition of an isolated hydrogen-bond system, K₃D(SO₄)₂, were observed at 15 K, and the space group of the low-temperature phase was determined. The anisotropic diffuse scattering around Bragg reflections in Fe-30.2 at.% Pd was also clearly observed in connection with a martensite phase transition.