THE EFFECT OF VARIOUS THERMAL TREATMENTS ON SUPERCOOLING OF PBTE MELTS

The supercooling of PbTe melts has been measured by thermal analysis as a function of various thermal treatments in an effort to understand how the supercooling is affected by the melt state. In the thermal treatments the maximum temperature, heating rate, cooling rate and holding time of the melts were varied. Two PbTe compounds of stoichiometric and non-stoichiometric composition are investigated. The degree of supercooling in the stoichiometric PbTe melt increases gradually with overheating and remains constant at overheatings higher than 20 K. For the non-stoichiometric Pb0.47Te0.53, the dependence of supercooling on the overheating shows different behavior in that supercooling is as large as 50 K at low overheating. From the heating rate and holding time dependence on supercooling, an intermediate melt structure is found to exist at 10 K overheating which gives a high supercooling of 25 K. It is also shown that the melt structure formed at high temperature is maintained at subsequent reduction of melt temperature, while the intermediate melt structure is destroyed according to the higher overheating.