The magnetic susceptibilities of liquid SbTe, BiTe, SbSe, and BiSe systems are measured by the Faraday method using a torsion balance. The decrease in diamagnetic susceptibility at the melting point is relatively large in liquid Bi2Te3 and Sb2Te3. On the other hand, it is considerably small in liquid Sb2Se3. This corresponds to the temperature change in the electrical conductivity reported previously. The value of susceptibility for liquid SbTe alloys is considerably different from the data measured by a previous author. It is clarified from the composition dependence of susceptibility that both liquid Te systems behave like metals rather than semiconductors in a wide range of composition. The composition dependence of susceptibilities in the liquid Se systems showes that in the Se-rich region the short-range bonding remains unchanged when melting, and these alloys take rapidly a metallic character with increasing metal content beyond the composition of Sb2Se3 or Bi2Se3. These experimental results are discussed using the bond orbital approximation.



Die magnetischen Suszeptibilitaten von flussigen SbTe-, BiTe-, SbSe- und BiSe-Systemen werden mit der Faraday-Methode mit einer Torsionswaage gemessen. Der Abfall der diamagnetischen Suszeptibilitat am Schmelzpunkt ist relativ gros in flussigem Bi2Te3 und Sb2Te3. Andererseits ist er in flussigem Sb2Se3 auffallig gering. Das stimmt mit der Temperaturanderung der elektrischen Leitfahigkeit uberein, wie fruher berichtet. Der Wert der Suszeptibilitat fur die flussigen SbTe-Legierungen ist betrachtlich verschieden von den Werten aus fruheren Arbeiten. Aus der Zusammensetzungsabhangigkeit der Suszeptibilitat wird gefunden, das sich beide flussigen Te-Systeme in einem grosen Bereich der Zusammensetzung eher wie Metalle als wie Halbleiter verhalten. Die Abhangigkeit der Suszeptibilitat von der Zusammensetzung zeigt, das in dem Sereichen Bereich die kurzreichweitigen Bindungen beim Schmelzen ungeandert bleiben, und das diese Legierungen mit zunehmendem Metallgehalt schnell einen metallischen Charakter annehmen, jenseits der Zusammensetzung von Sb2Se3 oder Bi2Se3. Diese experimentellen Ergebnisse werden mit der Orbital-Bindungsnaherung diskutiert.

The magnetic susceptibility of antimony and bismuth chalcogenides in the liquid state

The electrical conductivity and thermoelectric power of the molten In-Te system have been measured as a function of concentration and temperature. The electrical conductivity shows a minimum around the stoichiometric composition In2Te3. The temperature coefficient of the conductivity is positive between 30 and 100 at.% Te and shows a maximum at the composition In2Te3. The values of thermoelectric power are positive and large for the semiconducting region of the system.

Electrical properties of the molten In-Te system

Results are reported for the resistivity and thermoelectric power of three binary alloy systems in the liquid state, Ga-Te, Ge-Te, and Pb-Te. In two of these systems there is clear evidence for what may loosely be termed ‘compound formation’, at concentrations corresponding to Ga2Te3 and PbTe, and there is some sign that GeTe2 exists as a compound in the third. An attempt is made to classify the numerous Te-based systems which have now been studied in the liquid state, nearly all of which show evidence for compound formation, according to the nature of the bonding mechanism involved. The way in which the thermoelectric power varies with concentration is qualitatively the same for all the systems within one group, but there are significant differences between one group and the next.

The resistivity and thermoelectric power of liquid alloys containing tellurium

A molecular orbital model is proposed as the conceptual basis for the electronic structure of Tl–Te alloys. Using an expression proposed by Mott for the electrical conductivity in the strong scattering domain, existing data for the electrical conductivity σ and the thermopower S as a function of composition and temperature are compared with theory in the composition range where S is positive. This is done with the help of a theory for the equilibrium concentration of broken Te–Te bonds derived in another paper, with the dangling bonds assumed to give rise to holes. It is found that most of the observed behaviour of σ and S can be accounted for in a reasonable way. Reasons are discussed for the exceptions, which occur mainly in the behaviour of pure tellurium. We discuss the relation of our proposed model to the usual pseudo-gap model, and note a distinction between chain structures and network structures with regard to the mechanism whereby the density of states at the Fermi energy is affected by...

A molecular bonding theory for liquid thallium–tellurium alloys

Neuere Entwicklungen experimenteller Methoden fur die Messung thermodynamischer Grosen flussiger Legierungen mit besonderer Betonung der Kalorimetrie, der EMK- und der Knudsen-Methode werden besprochen. Ausgewahlte experimentelle Resultate thermodynamischer Untersuchungen wurden bezuglich des Auftretens von Anomalien analysiert, die auf partielle nichtmetallische Bindungen zuruckzufuhren sind. Diese Anomalien werden durch die Bildung heteroatomarer „Assoziate” erklart. Aufgrund veroffentlichter Ergebnisse werden Voraussagen uber das Auftreten von Anomalien in binaren Schmelzen gemacht.



Recent developments of experimental techniques for the measurement of thermodynamic quantities of liquid alloys are discussed with special emphasis on calorimetry, emf-measurements, and the Knudsen method. Selected experimental results of thermodynamic investigations are analyzed with respect to anomalies in the melts due to partial non-metallic bonding. An interpretation of the anomalies is given in terms of formation of heteroatomic “associates”. Available data have been checked to predict the occurrence of anomalies in binary melts.

Thermodynamik von Legierungsschmelzen: Meßmethoden und Ergebnisse

In the composition range 70 to 100 atomic % thallium, the phase diagram of Tl[sbnd]Te has a region with two immiscible phases below 600°c, corresponding to the separation of a metallic and a liquid semiconductor phase. We have made measurements of the electrical resistivity p ancl the Seebeck coefficient S at temperatures up to 850°c in the range in which the two liquid phases are mutually soluble in orcler to study the transition between metallic and semiconductor behaviour. As the concentration of tellurium is increased, p and the magnitude of S increase, and their temperature coefficients change from weakly positive values typical of metals to weakly negative values typical of liquid semiconductors with low resistivity. We find that the transport behaviour can be accounted for very well by a model which treats the alloy as a solution containing Tl2Te molecules plus metallic TI atoms. As Te is added to Tl2 electrons are removed from the conduction band, and scattering centres due to Tl2Te are a...

R. L. Peterson

Papers

Thermoelectric behaviour of molten Tl[sbnd]Te alloys at compositions approaching pure thallium