HIGH TEMPERATURE THERMOELECTRIC GENERATOR

The development continued of a 5-watt laboratory thermoelectric generator capable of operating at a hot junction temperature of 1200 deg C in a vacuum of .00001 mm Hg. Fourteen candidate junction materials were screened for use with MCC 50 in the production of thermocouple modules. Of these, C, Mo and W are being considered for the end product generator. Three methods for fabricating thermocouple modules with MCC 50 were studied and a hot-pre s/braze method selected for use in the making of modules for the end product. In sublimation rate loss tests conducted for 500 hr at 1200 deg C at .00001 to .000001 mm Hg, MCC 50 thermoelectric material l st only 0.53% weight. The rate of sublimation loss appears to decrease with time. Measurements of electrical properties of modules, before and after 100 hour tests at 1200 deg C, indicate the end product generator can be operated well beyond 1000 hrs, the design goal. Merit factors (Z) of MCC 50, based on extrapolations of thermal conductivity measurements from 1000 deg C, range from .0006 to .0011 per degree between 1200 and 1500 C. A 4-module prototype generator unit was constructed and is being tested at 1200 deg C in a vacuum.