X-ray topography of Ca_(0.5)Sr_(0.5)NdAlO_4 single crystal

摘要

A Ca_(0.5)Sr_(0.5)NdAlO_4 single crystal grown by the Czochralski method in the [100] direction was investigated by means of conventional projection X-ray topography, and by means of synchrotron white beam and monochromatic beam topography. The topographic investigation revealed growth striations with strong black diffraction contrasts distributed periodically in the form of concentric rings, and a significant number of resolved defects. Some of these defects seem to be associated with precipitates, while others form linear diffraction contrasts located perpendicularly to the striation stripes. The last category of defects can be somehow associated with dislocations, but provides much more intense and complex diffraction contrast that can be expected for individual dislocations. A significant lattice deformation associated with striation was revealed with some of the synchrotron topographic methods, particularly back-reflection white beam topography with fine mesh placed behind the crystal and transmission synchrotron section topography, where a characteristic bending of the section image was observed. The transmission section topographs provided also good visibility of segregation fringes in the plane intersected by the beam, corresponding to the subsequent positions of the growth surface.