Vaporization studies on elemental tellurium and selenium by Knudsen effusion mass spectrometry

• Published in: Journal of alloys and compounds Vol. 603; pp. 75 - 85
• Main Authors: Viswanathan, R., Balasubramanian, R., Darwin Albert Raj, D., Sai Baba, M., Lakshmi Narasimhan, T.S.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 05.08.2014; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Electron impact; Electrons and positron radiation effects; Enthalpy; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Knudsen effusion; Mass spectrometry; Physical radiation effects, radiation damage; Physics; Selenium; Selenium clusters; Specific phase transitions; Structure of solids and liquids; crystallography; Sublimation; Tellurium; Tellurium clusters; Thermochemistry; Vaporization; Vaporization of selenium; Vaporization of tellurium; Vaporization of selenium; Selenium clusters; Tellurium clusters; Vaporization of tellurium; Thermochemistry; Knudsen effusion; Fluence; Enthalpy; Sublimation; Vaporization; Partial pressure; Electron irradiation; Heat of formation
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2014.03.040

•A detailed KEMS study of vaporization of elemental tellurium and selenium systems.•Clusters Tei(g) (i=2 to 7) and Sei(g) (i=2 to 9) identified over Te(s) and Se(s).•p–T relations for Tei(g) (590 to 690K) and Sei(g) (380 to 480K).•Vapor phase of Te dominated by Te2(g) (∼95%) while that of Se by Se6(g) (∼50%) and Se5(g) (∼25%).•Sublimation and atomization enthalpies deduced for Tei(g) and Sei(g). Vaporization studies on elemental tellurium and selenium were conducted by Knudsen effusion mass spectrometry in the temperature range of 590–690K and 380–480K, respectively. The ionic species Tei+ (i=1–7) and Sei+(g) (i=1–9) were detected in the mass spectra over these two condensed phases. Measurement of ion intensities were performed as a function of electron impact energy and as a function of temperature (at different electron impact energies) for identifying the gaseous precursor species as well as for determining the partial pressure–temperature relations and sublimation enthalpies for these species. While the major species over elemental tellurium was confirmed to be Te2(g) (with all other gaseous species Te3–Te7 put together constituting less than 5%), the major species over elemental selenium was found to be Se6(g), closely followed by Se5(g) (with other gaseous species Se2–Se4 and Se7–Se9 put together also moderately constituting ∼25%). From the partial pressures, the thermodynamic data for the sublimation reactions i Te(s)=Tei(g) and i Se(s)=Sei(g) were deduced by second- and third-law methods. The atomization enthalpies of tellurium and selenium clusters were also deduced by using the recommended enthalpies of formation of monomeric species. Comparison of the findings obtained in the present study with those in previous studies revealed general agreement with regard to major species Te2(g) and Se6(g), but still some differences to be resolved with regard to minor species in both systems.