THE EFFECT OF VARIOUS THERMAL TREATMENTS ON SUPERCOOLING OF PBTE MELTS

The supercooling of PbTe melts has been measured by thermal analysis a s a function of various thermal treatments in an effort to understand how the supercooling is affected by the melt state. In the thermal tre atments the maximum temperature, heating rate, cooling rate and holdin g time of the melts were varied. Two PbTe compounds of stoichiometric and non-stoichiometric composition are investigated. The degree of sup ercooling in the stoichiometric PbTe melt increases gradually with ove rheating and remains constant at overheatings higher than 20 K. For th e non-stoichiometric Pb0.47Te0.53, the dependence of supercooling on t he overheating shows different behavior in that supercooling is as lar ge 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 m aintained at subsequent reduction of melt temperature, while the inter mediate melt structure is destroyed according to the higher overheatin g.