Study of the Vapor of the NaI ‐ ScI3 System: Vapor Composition, Thermochemistry of the Gaseous Heterocomplexes and , and Their Potential for Chemical Vapor Transport

Abstract

The vapor of the normalNaI‐ScI3 system was investigated under equilibrium conditions in the temperature range from 613 to 848 K by using Knudsen effusion mass spectrometry with a one‐ and a two‐compartment Knudsen cell. normalNaI/ScI3 samples of the compositions xnormalNaI=0.25 normaland 0.75 were studied with the one‐compartment cell. The gaseous species normalNaI , false(normalNaI)2 , ScI3 , false(ScI3)2 , NaScI4 , and Na2ScI5 were present in the vapor. Their partial pressures were employed in a second‐law evaluation yielding for the first time reliable thermodynamic data on the gas phase chemistry of the normalNaI‐ScI3 system. The enthalpy and entropy changes of the reactionsNaScI4)(normalg⇄normalNaI)(normalg+ScI3)(normalgfalse)false[1false] Na2ScI5)(normalg⇄2normalNaI)(normalg+ScI3)(normalg false[2false] NaI2)(normalg+normalScI32)(normalg⇄2NaScI4)(normalg false[3false]resulted as normalΔH2980=228±5 kJ mol−1 , normalΔS2980=165±8Jmol−1 K−1 for reaction Eq. [1]; normalΔH2980=388±9 kJ mol−1 , normalΔS2980=310±13Jmol−1 K−1 for reaction Eq. [2]; and normalΔH2980=−87±6 kJ mol−1 , normalΔS2980=−31±8Jmol−1 K−1 for reaction Eq. [3]. The following equilibrium constants were obtained for the dissociation reactions Eq. [1] and [2]logKnormalp=−11,652 1/)(T/K+8.0533 normalfor Eq.false[1false])(613–848KandlogKp=−19,747 1/)(T/K+15.088 normalfor Eq.false[2false])(623–848KThe data are discussed generally as well as with respect to their significance for chemical vapor transport in metal halide lamps and for the prediction of the dissociation enthalpy of gaseous heterocomplexes by a semiempirical rule.

High temperature mass spectrometry in materials research

“…The potential of the 1:l heterocomplexes for sodium enhancement can be predicted from the data in Table 5 (see e.g., Refs. 29,32).…”

Determination of the thermodynamic activities of NaBr and DyBr3 in the phases of the NaBr–DyBr3 system at 863 K by Knudsen effusion mass spectrometry

“…Refs. [3][4][5][6][7]) which were carried out for the development of metal halide lamps. The results are summarized in a review article [8].…”

“…), respectively: a(NaBr) 1 = I(NaBr + )/I(Na 2 Br + ) {I(NaBr + )/I(Na 2 Br + )} a(NaBr)=1 (4) a(NaBr) 2 = I(Na 2 DyBr 4 + )/I(NaDyBr 3 + ){I(Na 2 DyBr 4 + )/I(NaDyBr 3 + )} a(NaBr)=1(5) …”

Μελετη Συστηματων Ιωδιουχων Λανθανιδων-Ιωδιουχων Αλκαλιων Με Φασματοσκοπια Raman Και Φασματομετρια Μαζας

“…Gavrilin et al (1987), 21 Hilpert και Miller (1990). 23 Lanthanide and alkali iodides are used in high intensity discharge mercury lamps in order to improve the overlapp between the emission spectrum of the lamp and the eye sensitivity curve. Improvement of the overlapp between the emission spectrum of the lamp and the eye sensitivity curve results in higher luminous efficacy of the lamp, (Im/W), and considerable energy saving.…”

“…6-1 φαίνονται οι ευθείες του Πίνακα Π2, καθώς και τα πειραματικά σημεία.Από την ολική ένταση των ιόντων πάνω από το Nal υπολογίζεται ο συντελεστής αναλογίας β της εξίσωσης Ρ = β. (Π), που χρησιμοποιείται για τη μετατροπή των εντάσεων σε απόλυτες πιέσεις" στην περιοχή μαζών23 -150 amu. Ο αναλυτικός υπολογισμός της τιμής β δίνεται στον Πίνακα ΠΙΟ.…”