Vaporization thermodynamics of (iron + tellurium): a high-temperature mass-spectrometric study

Sai Baba, M. ; Viswanathan, R. ; Balasubramanian, R. ; Darwin Albert Raj, D. ; Saha, B. ; Mathews, C. K. (1988) Vaporization thermodynamics of (iron + tellurium): a high-temperature mass-spectrometric study Journal of Chemical Thermodynamics, 20 (10). pp. 1157-1173. ISSN 0021-9614

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Vaporization of (iron + tellurium) alloys was studied using Knudsen-effusion mass spectrometry. The partial pressures of Te2(g) and Te3(g) over the two-phase fields {FeTe0.939(s) + FeTe1.994(s)} and {FeTe0.939(s) + FeTe1.451(s)} were determined in the temperature ranges 659 to 759 K and 803 to 818 K, respectively. The partial pressures over the two-phase field {FeTe0.939(s) + FeTe1.427(s)} were determined at 868 K. Enthalpy or Gibbs energy changes were derived from the partial pressures for the equilibria: FeTex(s) = FeTey(s) + {(x-y)/i}Tei(g), where x = 1.994 (ε-phase), 1.451 (δ'-phase), and 1.427 (δ-phase), and y = 0.939 (β-phase) with i = 2 or 3. The phase boundaries of the β-phase at 868 K were delineated by a continuous monitoring of the intensity of Te2+ as a function of time, starting with a sample having 72.9 mass per cent of Te. Activities of Te were determined and those of Fe computed as a function of composition of the β-phase, using Gibbs-Duhem integration. Chemical potential differences of Te and Fe and, thus, the Gibbs free energy of formation of the β-phase, were deduced across the homogeneity range. Enthalpies or Gibbs free energies of formation of the phases β, ε , δ' and δ were derived.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
ID Code:25449
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