Origin of Imperfections in ⟨100⟩ SrLaAlO$\text{}_{4}$ Crystals

In Czochralski-grown SrLaAlO$\text{}_{4}$ crystals with ⟨100⟩ orientation, (001) planar faults extending through the entire crystal boule can frequently be observed. Chemical etching and transmission electron microscopy including energy dispersive X-ray spectroscopy were used to characterise their nucleation sites, these being located in the upper part of the crystal cone. Three serious sources were found: (1) lateral {001} facets, (2) grown-in defects in the seed, and (3) small particles of a second phase in the interior of the cone. These particles were identified as trigonal and cubic form of lanthanum oxide with a different Sr content