Method for producing lead telluride thermoelectric elements by vacuum hot-pressing

Claim 1

A METHOD FOR MANUFACTURING FINE GRAIN POLYCRYSTALLINE SEMICONDUCTIVE LEAD TELLURIDE THERMOELECTRIC ELEMENTS HAVING AN ULTIMATE COMPRESSIVE STRENGTH OF ABOUT 25,000 POUNDS PER SQUARE INCH AND A DENSITY APPROXIMATELY 99.5 PERCENT OF THEORETICAL DENSITY COMPRISING THE STEPS OF PLACING A DESIRED AMOUNT OF SAID LEAD TELLURIDE POWDER IN THE DIE RECEPTACLE OF A PUNCH AND DIE FORMING SET COMPOSED OF A MATERIAL WHICH IS NONREACTIVE WITH SAID POWDER AT ANY TEMPERATURE UP TO THE MELTING POINT OF SAID POWDER AND FROM WHICH PUNCH AND DIE SET CONTAMINATING REACTIVE ATMOSPHERIC GASES HAVE PREVIOUSLY BEEN REMOVED WHILE SUBSTANTIALLY EXCLUDING REACTIVE ATMOSPHERIC GASES FROM SAID PUNCH AND DIE SET AND SAID POWDER, ASSEMBLING SAID PUNCH AND DIE FORMING SET CONTAINING SAID POWDER WHILE SUBSTANTIALLY EXCLUDING REACTIVE ATMOSPHERIC GASES FROM SAID OUNCH AND DIE AND SAID POWDER, DEGASSING SAID ASSEMBLY AND CONTAINED POWDER BY MAINTAINING SAID ASSEMBLY AND CONTAINED POWDER WITHIN A VACUUM ENVIRONMENT FOR A PERIOD OF TIME SUFFICIENT TO SUBSTANTIALLY REMOVE ANY OCCLUDED GASES, HEATING SAID ASSEMBLY TO A TEMPERATURE OF FROM ABOUT 400* TO ABOUT 500*C. WHILE SUBSTANTIALLY EXCLUDING REACTIVE ATMOSPHERIC GASES FROM SAID ASSEMBLY AND CONTENTS, APPLYING A PRESSURE OF AT LEAST 1000 P.S.I. ON SAID PUNCH OF SAID ASSEMBLY TO COMPRESS THE POWDER CONTAINED WITHIN SAID DIE RECEPTACLE WHILE SIMULTANEOUSLY INCREASING THE TEMPERATURE OF SAID POWDER TO A TEMPERATURE IN THE RANGE BETWEEN ABOUT 500*C. TO ABOUT 850*C. WHILE MAINTAINING SAID ASSEMBLY AND CONTENTS AT SUBATMOSPHERIC PRESSURE AND SUBSTANTIALLY EXCLUDING REACTIVE ATMOSPHERIC GASES THEREFROM, MAINTAINING SAID PRESSURE AND TEMPERATURE TO SAID POWDER FOR A TIME SUFFICIENT TO ACHIEVE A COMPACT DENSITY OF AOUT 99.5 PERCENT OF THE THEORETICAL DENSITY, COOLING SAID COMPACT TO A TEMPERATURE OF ABOUT 50*C. TO 150*C. AND REMOVING THE COMPACTED THERMOELECTRIC ELEMENT FROM SAID PUNCH AND DIE SET.

Claim 2

A METHOD FOR MANUFACTURING FINE GRAIN POLYCRYSTALLINE SEMICONDUCTIVE LEAD TELLURIDE THERMOELECTRIC ELEMENTS HAVING AN ULTIMATE COMPRESSIVE STRENGTH OF ABOUT 25,000 POUNDS PER SQUARE INCH AND A DENSITY APPROXIMATELY 99.5 PERCENT OF THEORETICAL DENSITY COMPRISING THE STEPS OF PLACING A DESIRED AMOUNT OF SAID LEAD TELLURIDE POWDER IN THE DIE RECEPTACLE OF A PUNCH AND DIE FORMING SET COMPOSED OF A MATERIAL WHICH IS NONREACTIVE WITH SAID POWDER AT ANY TEMPERATURE UP TO THE MELTING POINT OF SAID POWDER AND FROM WHICH PUNCH AND DIE SET CONTAMINATING REACTIVE ATMOSPHERIC GASES HAVE PREVIOUSLY BEEN REMOVED WHILE SUBSTANTIALLY EXCLUDING REACTIVE ATMOSPHERIC GASES FROM SAID PUNCH AND DIE SET AND SAID POWDER, ASSEMBLING SAID PUNCH AND DIE FORMING SET CONTAINING SAID POWDER WHILE SUBSTANTIALLY EXCLUDING REACTIVE ATMOSPHERIC GASES FROM SAID OUNCH AND DIE AND SAID POWDER, DEGASSING SAID ASSEMBLY AND CONTAINED POWDER BY MAINTAINING SAID ASSEMBLY AND CONTAINED POWDER WITHIN A VACUUM ENVIRONMENT FOR A PERIOD OF TIME SUFFICIENT TO SUBSTANTIALLY REMOVE ANY OCCLUDED GASES, HEATING SAID ASSEMBLY TO A TEMPERATURE OF FROM ABOUT 400* TO ABOUT 500*C. WHILE SUBSTANTIALLY EXCLUDING REACTIVE ATMOSPHERIC GASES FROM SAID ASSEMBLY AND CONTENTS, APPLYING A PRESSURE OF AT LEAST 1000 P.S.I. ON SAID PUNCH OF SAID ASSEMBLY TO COMPRESS THE POWDER CONTAINED WITHIN SAID DIE RECEPTACLE WHILE SIMULTANEOUSLY INCREASING THE TEMPERATURE OF SAID POWDER TO A TEMPERATURE IN THE RANGE BETWEEN ABOUT 500*C. TO ABOUT 850*C. WHILE MAINTAINING SAID ASSEMBLY AND CONTENTS AT SUBATMOSPHERIC PRESSURE AND SUBSTANTIALLY EXCLUDING REACTIVE ATMOSPHERIC GASES THEREFROM, MAINTAINING SAID PRESSURE AND TEMPERATURE TO SAID POWDER FOR A TIME SUFFICIENT TO ACHIEVE A COMPACT DENSITY OF AOUT 99.5 PERCENT OF THE THEORETICAL DENSITY, COOLING SAID COMPACT TO A TEMPERATURE OF ABOUT 50*C. TO 150*C. AND REMOVING THE COMPACTED THERMOELECTRIC ELEMENT FROM SAID PUNCH AND DIE SET.