Vaporization studies on (manganese  +  tellurium) withx(Te)  >  0.5 by Knudsen effusion mass spectrometry

✍ Scribed by T.S. Lakshmi Narasimhan; ; M. Sai Baba; ; R. Balasubramanian; ; S. Nalini; ; R. Viswanathan

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 195 KB
• Volume: 34
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.2001.0871

✦ Synopsis

Vaporization studies on {(1 -x)Mn + xTe} samples, where x = (0.549, 0.599, 0.718, 0.720, and 0.741) were conducted by Knudsen effusion mass spectrometry. Experiments with the first two samples yielded vapor pressures for the two-phase region (manganese ditelluride + manganese monotelluride) in the temperature range 650 K to 750 K: lg{ p(Te 2 )/Pa} = -(10010 ± 98)/(K/T ) + (13.421 ± 0.140). The vaporization reaction MnTe 1.87 (s) = MnTe 1.03 (s) + 0.42Te 2 (g) was evaluated: r H o m (298.15 K) = (80.7 ± 2.2) kJ • mol -1 . Combining this with literature values for f H o m (298.15 K) for Te 2 (g) and the MnTe phase, we deduced that f H o m (MnTe 1.87 , s, 298.15 K) = -(111.4 ± 7.2) kJ • mol -1 . The last three samples, corresponding to the two-phase region (manganese ditelluride + tellurium) were subjected to long, predominantly isothermal, experiments. They served to show that the MnTe 2 phase exists from x(Te) = (0.651 to 0.670) at 650 K T 675 K, besides yielding p(Te 2 ) at various x(Te)s across the homogeneity range of MnTe 2 , and confirming the reliability of the vapor pressure equation given above. These results also rendered it possible to deduce f H o m (298.15 K) for the MnTe 2 phase corresponding to the formulas for the Te-rich and Mn-rich boundaries: f H o m (MnTe 2.03 , s, 298.15 K) = -121.6 kJ • mol -1 , and f H o m (MnTe 1.87 , s, 298.15 K) = -120.2 kJ • mol -1 . The latter, in combination with r H o m (298.15 K) and f H o m (Te 2 , g, 298.15 K), yielded f H o m (MnTe 1.03 , s, 298.15 K) = -108.0 kJ • mol -1 .