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Title: X-ray identification of n-PbTe sublimate and the dependence of the rate of sublimation on the cover gas pressure
Authors: Dughaish, Z.H.
Rowe, D.M.
Keywords: X-ray
Issue Date: 2001
Publisher: King Saud University
Citation: Journal of the King Saud University: 13 (1&2); 27-35
Abstract: Lead telluride and its related materials sublimate at high temperature. This could result in a change in stoichiometry due to the preferential loss of one of the constituents, which in turn alters the carrier concentration hence the thermoelectric properties of the material. The onset of sublimation started at 838K and a cover gas pressure of 1.38XIOsNm.2. Negligible mass losses (<lO-8kg) were noticed during the heating cycle below 838K, but became detectable above 923K. Losses increased as the temperature approached 973K. X-ray studies showed that PbTe sublimes as molecular PbTe and not as Pb or Te atoms, accompanied by a slight shift in stoichiometry towards Te-deficiency. The rate of sublimation decreased significantly with increasing cover gas pressure when heated at 973K. A reduction of 50% in the rate of sublimation is achieved when the cover gas pressure varied from 1.722XlOsNm-2 to 3.79xloSNm'2. A further reduction in the rate of sublimation could be achieved by applying higher gas pressures provided the equipment can withstand it. The measured rate of sublimation at 973K is 30 per cent lower than the calculated rate as predicted by theory.
Description: * Department of Physics, College of Science, King Saud University, PO Box 2455, Riyadh 11451 Saudi Arabia and **School of Electrical, Electronic and Systems Engineering, University of Wales, P.O. Box 917, New Port Road, Cardiff CF2 1XH, United Kingdom
URI: http://hdl.handle.net/123456789/1435
Appears in Collections:King Saud University Initial Collection

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