Study on cracking and low-angle grain boundary defects in YAlO 3 crystal

Abstract

Dislocation low-angle grain boundary (mosaic structure) and cracking in yttrium orthoaluminate (YAlO 3) crystal grown by the Czochralski method were studied using scanning electron microscopy (SEM), X-ray, etching, and optical techniques. From dislocation etch pits, the boundary angle of mosaic structure on the (010) plane was estimated to be 56.5°. The rocking curves of four-crystal high-resolution X-ray diffraction (XRD) show that the boundary angle on the plane normal to (010) is 58°. Thermal expansion behavior of Ce:YAlO 3 was studied along several main crystallographic axes between 20 and 800 °C, and the result shows that there is a large difference in expansion coefficients between [010] and [101¯], which is considered to lead the cracking.