FIRST DIFFRACTION TOPOGRAPHIC RESULTS AT A 3RD GENERATION SYNCHROTRON-RADIATION FACILITY - APPLICATION TO CRYSTALS UNDER AN ELECTRIC-FIELD

Diffraction topographic techniques allow the observation of inhomogene ities (defects, domains,...) within a single crystal. The unique capab ilities of third generation synchrotron radiation facilities, like the ESRF, add new possibilities to these techniques: (1) the exposure tim e to record a topograph can be reduced to similar to 10(-2) s, i.e. a factor 10(2)-10(3) below the present standards; (2) an improved resolu tion associated with the small. source size, even when setting the fil m far (similar to 60 cm) from the sample, allows the size of the sampl e environment devices to be increased; (3) high sensitivity to small ( greater than or equal to 10(-7)) distortions (misorientations and/or l attice parameter variations); (4) investigation of thick or heavy mate rials, which were up to now the exclusive field of neutron diffraction . We briefly describe the future Topography and High Resolution Diffra ction beamline ID 19, which is designed to optimize the required exper imental conditions, and which will be operational at the end of 1995. The first topographic white beam experiments which illustrate these ne w possibilities were carried out on two (ID11 and D5) of the presently operational beamlines of the ESRF. In this work, particular attention is dedicated to observations performed on crystals under an electric field (alpha-LiIO3, KTP, LiNbO3). Very interesting and encouraging res ults were obtained, particularly when using ''section'' topography.