Errors in the determination of void volumes by transmission electron microscopy

The determination of void volumes from transmission electron micrographs is an essential part of evaluating the void swelling in irradiated materials. Three commonly-used methods of determining the void volume are investigated. The apparent change in the volume of octahedral voids in f.c.c. metals with orientation and void truncation is calculated. The resulting error in void voluinc can be as great as 60% if the void geometry is not taken into account. The socalled matching area method is found to be least sensitive to orientation and truncation and leads to less than ± 10% error in void volume at orientations near [110]. This method is therefore the most suitable for routine void measurements.