The crystal system and space group of (formula presented) with a distorted perovskite structure were investigated by convergent-beam electron diffraction (CBED), selected area electron diffraction, and x-ray diffraction using synchrotron radiation. Since all the observed CBED patterns showed a symmetry of 1, and the (formula presented) dark-field disk of CBED patterns indicated the absence of an inversion center in (formula presented) the crystal symmetry of (formula presented) was concluded to be triclinic with a space group of (formula presented) (No. 1). The diffraction angles of the x-ray-diffraction peaks of (formula presented) obtained using synchrotron radiation, could apparently be explained by assuming a monoclinic symmetry. However, a larger full width at half maximum (FWHM) of the 440 peak, indexed assuming a monoclinic symmetry other than that of each peak of 008, (formula presented) 404, and 044 could not be explained. The large FWHM of the 440 peak could be attributed to an overlapping of the (formula presented) and 440 peaks of triclinic symmetry, showing agreement with the result of CBED.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2001|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics