Measurements have been made of the lattice parameter of silver bromide at room temperature and in the range from about 350 to 420°C. The results are compared with the values obtained on the basis of two contrary assumptions: first, that the lattice expansion is identical with the external expansion measured by Strelkow; and second, that some of the external increase in volume is caused by formation of vacancies, the resultant parameter being that estimated by Lawson. Within experimental error, the measured curve agrees with the first assumption, which is equivalent to the assumption that no Schottky defects have formed. Since it is known from ionic conductivity measurements that there are about 2 percent of defects at temperatures near 420°C, it is concluded that these are Frenkel defects. However, the magnitude of the errots involved in the measurements is such that the existence of a small number (about 10 percent of the total) of Schottky defects cannot be entirely precluded.

• Received 4 January 1951

DOI:https://doi.org/10.1103/PhysRev.82.422