TEM Method for Identification of Domains in Materials which Undergo a Pm3m3->R3c or R3c Phase Transition

The c-axis of the domains formed by a Pm3m→R3c or R3¯c phase transition may lie along any of the four 〈111〉 C directions of the cubic phase. It is shown that the orientation of the c-axis can be determined by TEM by examining whether two suitable 1/3{113}C superlattice reflections are allowed or forbidden in the trigonal phase. As an example, the method is used to examine domains in LaAlO3