Crystallographic Orientation Relationships Between SrTiO3 and Ruddlesden‐Popper Phase

Abstract

The crystalline phase mixture and microstructure of SrO‐excess SrTiO3 powder sintered at 1350°C/4 h is analyzed using X‐ray diffractometry (XRD), and scanning and transmission electron microscopy (SEM and TEM). Second phases represented by Ruddlesden–Popper Sr3Ti2O7 (RP2) and Sr4Ti3O10 (RP3) coexist with SrTiO3 (ST), consistent with the SrO–TiO2 phase equilibrium diagram. Some ST grains contain inter‐grown RP2 lamellae that permits analysis of the ST‐RP2 interface. The ST‐RP2 boundary shared by (001)ST and (001)RP2, although containing a lattice mismatch, is accommodated by long‐range elastic strain. The crystallographic orientation relationships of ST and RP2 at the interface are determined by selected area diffraction patterns (SADP) and described by transformation matrices. The crystallographic shear structure across the ST–RP boundary exhibiting the characteristic α‐fringe pattern can be represented by a fault vector R = 1/2(111)ST.