Polymorphic transitions in CdS and CdSe as probed by dilatometry

Polymorphic transitions in CdS and CdSe were studied on a dilatometric setup that comprised an evacuated quartz ampoule containing a sample, in which a cadmium vapor pressure was created to keep the sample from subliming at high temperatures. Measurements were carried out at temperatures in the range 100–1050°C. The test samples were found to experience jumpwise changes in their lengths during heating (at 270 and 760°C in CdS and at 690 and 980°C in CdSe). Cooling induced similar changes (a jumpwise shortening of the length of a sample). Thus, a clear-cut and well reproducible hysteresis was observed in heating-cooling measurement sets. Topics of CdS and CdSe technology are discussed in terms of polymorphic transitions.