A SIMPLE AND RAPID METHOD FOR DETERMINING ORIENTATIONS AND MISORIENTATIONS OF CRYSTALLINE SPECIMENS IN TEM

A new method for determining orientations and misorientations of a crystalline specimen has been developed using a double-tilt holder for a transmission electron microscope (TEM). After tilting the specimen to allow one of the low-index zone axes for one crystallite to be close to the beam direction, the orientation of any crystallite can be obtained by determining the relative position of the Kikuchi pattern on the screen. Then, for one interesting area containing many crystallites which have closely related orientations (difference less than 15 degrees), the orientations of the different crystallites can be determined by just moving the specimen to obtain the Kikuchi patterns from these crystallites and determining their relative positions on the screen. The misorientations between any selected pair of crystallites can then be calculated. The accuracy for determining the orientation of any particular crystallite is about 1 degrees and in the case of determination of misorientation angles and axes between two crystallites the accuracies are 0.3 degrees and 3 degrees respectively. Comparing with the previous standard methods used so far, the present technique is considered to be much simpler and more rapid for determining crystal orientations in TEM.