Characterisation of the Defect Structure in Gadolinum Orthovanadate Single Crystals Grown by the Czochralski Method

The $GdVO_4$ single crystals, both undoped and doped with erbium or thulium, were studied by means of X-ray diffraction topographic methods exploring laboratory and synchrotron radiation sources. Variously developed block structure, caused probably by thermal stresses, was revealed. The highest crystallographic perfection was observed in the crystal doped with 4 at.% of thulium, which was free of the grain boundaries in the end part. Contrary to that, the differences in structural perfection between samples cut out from various regions of the crystal and for different kinds of doping, were less distinct in other crystals. The diffraction topographic methods enabled the statement that the misorientation between various blocks is in the range of several arc minutes.