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The perfection of YVO4 crystals, which are predicted to replace formerly used YAG garnets due to higher quantum efficiency and lower excitation level, was studied. The investigations of Czochralski grown undoped YVO 4 single crystals were performed mainly by means of X-ray topographic methods. Both synchrotron and conventional X-ray sources were used. The study revealed relatively high density of weak point-like contrasts which can be most probably interpreted as dislocation outcrops. In regions of the crystal close to its boundary we observed glide bands. It was also found that in some regions the dislocations form local subgrain boundaries. The white beam back reflection and monochromatic beam topography allowed to evaluate a local misorientation which not exceeded several angular minutes. No segregation fringes were observed proving a good homogeneity of chemical composition.

Samples cut out from different regions of SrLaGaO4 (SLG) single crystal grown along [001]‐direction were studied with a number of X‐ray diffraction topographic methods exploring both conventional and synchrotron X‐ray sources. The synchrotron investigation included in particular white beam projection transmission topography at ultra short wavelength and taking monochromatic beam topographs at different points of the rocking curves at different azimuths. The methods enabled the evaluation of the character of lattice deformation connected with the characteristic ‘rod‐like’ defects observed in the core region of the crystal. A shrinkage of the material inside the defects was indicated.