Connecting electronic entropy to empirically accessible electronic properties in high temperature systems

Abstract

A quantitative theoretical model connecting the thermopower and electronic entropy of molten systems is proposed, the validity of which is tested for semiconductors and metallic materials. The model accurately provides the entropy of mixing for molten semiconductors, as shown for the representative system Te-Tl. Predictions of the electronic entropy of fusion for compounds are in agreement with available data and offer a novel means to identify the correct electrical conductivity model when Hall measurements are not available. Electronic entropy for molten semiconductor and metallic systems is shown to reflect order in the molten and solid state. The model proves accurate at predicting the electronic state entropy contribution to the electronic entropy of mixing.

Experimentally Determined Phase Diagram for the Barium Sulfide-Copper(I) Sulfide System Above 873 K (600 °C)

“…Considering the large difference in electronic properties of the molten end members Cu 2 S and BaS, operating in the miscibility gap may offer unconventional features for such materials systems. Indeed, the recent results attributing the presence of miscibility gaps in liquid semiconductors to electronic entropy/electronic transport properties differences [20,21] suggest the properties of the two liquids identified in this studyand seen in Figure 4 and 5will be drastically different. The BaS-rich, heavier, more ionic liquid would be a strong candidate for use in electrochemical applications requiring an ionically-conductive liquid, while the Cu 2 S-rich, lighter liquid would have properties more similar to a molten semi-conductor.…”

Molten Semiconductors for High Temperature Thermoelectricity

“…33 Therefore, the frontiers in materials science and engineering of molten semiconductors reside in the ability to predict thermodynamics (e.g. quantitatively connecting thermodynamic mixing properties to the electronic properties of molten systems 53 ) and transport properties in order to envision novel compositions with higher intrinsic thermoelectric properties as well as the design of large-scale devices that help mitigate natural convection.…”

A thermodynamic basis for the electronic properties of molten semiconductors: the role of electronic entropy

“…A description of molten semiconductors is available in reference [5]. These systems exhibit semiconducting properties in the molten state.…”

“…In contrast, the slope of the line fit to the SC-M data in Figure 2 is 41.2 J mol -1 K -1 . This reflects the dramatic decrease in short-range order upon melting of these semiconducting compounds, which contributes a large configurational entropy of fusion as well as a large electronic entropy of fusion [3,5,6,9,10].…”

“…Fultz predicted that the study of the electronic entropy of high temperature systems would be valuable for the prediction of high temperature material properties [4]. In our previous work on molten semiconductors [5], we discussed the various contributions to entropy and demonstrated a quantitative connection between the electronic state entropy * , the electronic properties of molten systems, and their total mixing entropy. We herein leverage this connection to show how electronic entropy is at the origin of the qualitative correlation reported in the prior art.…”