THE TEMPERATURE-COMPOSITION PHASE-EQUILIBRIA IN THE HGTE-HGI2 PSEUDOBINARY SYSTEM

The temperature-composition phase diagram of the HgTe-HgI2 pseudobinar y system was determined between 25 and 670 degrees C using differentia l scanning calorimetry, differential thermal analysis, Debye-Scherrer powder X-ray diffraction techniques, and metallographic analysis metho ds. Solid solutions of HgTe and HgI2 with the cubic, zinc blende-type structure exist above 300 degrees C, having a maximum solubility of 11 .7 +/- 0.8 Mol-% HgI2 in HgTe at 501 +/- 5 degrees C. The monoclinic i ntermediate phase Hg3Te2I2 is formed by a peritectic reaction upon coo ling at 501 +/- 5 degrees C, with the peritectic point at approximatel y 37 +/- 4 Mol-% HgI2. The previously unknown cubic phase Hg(3)TeL(4) (a = 6.240+/-0.003 Angstrom) is formed by a eutectoid reaction at 238/-3 degrees C and is stable up to 273+/-3 degrees C, where it melts by a peritectic reaction with the peritectic point at approximately 79+/ -3 Mol-% HgI2. Between Hg3TeI4 and HgI2 is a eutectic point at 82+/-3 Mol-% HgI2 and 250+/-3 degrees C. The alpha to beta transition of HgI2 at 133+/-3 degrees C is independent of sample composition between 33. 3 and 100 Mol-% HgI2.