Antimony and Bismuth Tellurides

The 3,3 -diaminobenzidine method has been applied for determination of Se in biological materials [28,66], soils [67], air [68], silicates [11], sulphide ores [1], copper [8,14,18], organic substances [69], lead [8,14], steel [29], antimony and bismuth tellurides [70], thin Cd-Se films [71], silver chloride and uranium oxide [12],... 

INVESTIGATION OF THE EVAPORATION OF ANTIMONY AND BISMUTH TELLURIDES AND OF BISMUTH SELENIDE ... 

Measurements were made of the saturation vapor pressure of solid antimony and bismuth tellurides and of bismuth selenide. It was found that the evaporation of these compounds was of a dissociative nature, in accordance with the following equations... 

We prepared antimony and bismuth tellurides and bismuth selenide by the fusion of the components in evacuated and sealed ampoules. The antimony, bismuth, and selenium were of the Su-0, V-0, and "rectifier" grades. The tellurium was of 99.99% purity. 

The heats of dissociative evaporation of antimony and bismuth tellurides, calculated using the second and third laws of thermodynamics, are in good agreement. This shows that the suggested dissociative evaporation schemes predominate in the investigated temperature intervals. According to [1], the dissociative process... 

If the temperature is increased by a few tens of degrees above the values used in our experiments, the condensate resulting from the evaporation of bismuth selenide is found to be rich in selenium. However, the good agreement between the heat of formation AH298 of Bi2Se3 calculated usii the third law on the basis of Eq. (8) and that deduced from thermochemical measurements [7] shows that the dissociative evaporation process predominates also in the case of bismuth selenide but is accompanied by the parallel process of thermal dissociation. Antimony and bismuth tellurides can also dissociate thermally but such dissociation is relatively unimportant in the invest ated range of temperatures. 

Measurements were made of the vapor pressures of solid antimony and bismuth tellurides and of solid bismuth selenide. 

The tin(II) and lead(II) tellurides result from the amide M N(SiMe3)2k and tellurol. The tin derivative is dimeric with the Sn2Te2 unit adopting a butterfly-like structure with the terminal tellurol groups cis109. The antimony and bismuth derivatives result from amides and the tellurol96. 

X 10 cm , and = 2.4lA obtained from a comparison of molecular properties of the sulphides, selenides, and tellurides of arsenic, antimony, and bismuth. These parameters were used by Uy and Drowart [69UY/DRO] in their calculation of the dissociation energy of BiSe(g) from mass-spectrometric measurements at high temperatures. 

The dissociative evaporation of antimony telluride differs from the evaporation of bismuth selenide and telluride. The cause of this difference becomes obvious when we compare the molecular compositions of the metallic antimony and bismuth vapors. The principal component of the antimony vapor at temperatures and pressures corresponding to our measurements is... 

Johann Heinrich Biltz (Berlin, 26 May 1865-Breslau, 29 October or 2 November 1943), a pupil of Victor Meyer, professor in Breslau (1911), determined the vapour densities of stannous chloride, cuprous and silver chlorides, phosphorus, sulphur, selenium, tin, arsenic, antimony and bismuth, detecting the molecule Sg. His later work was largely on organic chemistry. His brother Eugen Wilhelm Biltz (Berlin, 8 March 1877-Heidelberg, 13 November 1943) was professor in Gottingen (1900), Clausthal (1908), and Hannover. He published an immense number of papers, on colloids, the conductivities of fused salts, the compounds of ammonia with salts, compounds of beryllium and other rarer metals, sulphides, phosphides and tellurides, etc., and the molecular volumes of solid compounds. ... 

Thermoelectric cooling devices, treated in Chapter 46 Arsenic, Antimony and Bismuth, with bismuth telluride as semiconductor material, are utilized for cooHng purposes. 

Seebeck experimented with a number of metals including antimony, iron, zinc, silver, gold, lead, mercury, copper, platinum, and bismuth. Later, the observation was made that the electromotive force (EMF) generated is proportional to the temperature difference between the junctions. Today, TE couples are often made from semiconductor alloys of bismuth antimony telluride, Bi Sb2- cTe3 (x 0.5), that have been suitably doped to possess distinct n- or p-type characteristics. A practical TE cooler consists of one or more couples that are connected electrically in series and thermally in parallel. 

Antimony is also used as a dopant in -type semiconductors. It is a common additive in dopants for silicon crystals with impurities, to alter the electrical conductivity. Interesting semiconductor properties have been reported for cadmium antimonide [12050-27-0], CdSb, and zinc antimonide [12059-55-9], ZnSb. The latter has good thermoelectric properties. Antimony with a purity as low as 99.9+% is an important alloying ingredient in the bismuth telluride [1504-82-1], Bi Te class of alloys which are used for thermoelectric cooling. 

Our investigation shows that the vapor pressures of solid bismuth and antimony tellurides and of bismuth selenide are quite low. The working temperatures of thermoelements made of these substances do not exceed 700 C. Under such conditions, the evaporation of thermoelements should be of little significance, especially as the loss of matter from open surfaces occurs at a rate which is 6—65 times slower than the equilibrium rate of evaporation. The values of the evaporation coefficient (0.15-0.16) found in our study show that the evaporation process is fairly complex. This is supported by thermodynamic calculations, which demonstrate that the evaporation is of a dissociative nature. 

Trivalent bismuth and antimony tellurides and selenides are the most interesting among the compounds formed in the Bi-Te, Bi—Se, Sb—Te, and Sb—Se systems [1—4]. Solid solutions of these compounds are used widely as thermoelectric materials. 

The thermodynamic properties of the higher bismuth and antimony tellurides and selenides have been investigated by many authors but the results are contradictory. 

The purpose of our study was to determine the thermod3mamic properties of bismuth and antimony tellurides and selenides by the emf method. 

The electrolyte in the measurements of the thermodynamic properties of bismuth sele-nide and telluride and of antimony telluride was the easily melted mixture of anhydrous zinc chloride (analytic purity) with sodium and potassium chlorides (chemical purity grade). The melting point of this mixture was Tmp — 208 C. The thermodynamic properties of antimony selenide were determined using a mixture of aluminum chloride (distilled twice in vacuum) and sodium chloride (chemical purity grade). The meltii point of this mixture was Tmp = 150-155°C. 

TABLE 2. Thermodynamic Properties of Higher Bismuth and Antimony Tellurides and Selenides... 

It follows from Tables 2 and 3 that the thermodynamic properties obtained in our investigation were in good agreement with those deduced using a solution calorimeter (the solvent was liquid bismuth at T = 623°K) [7] and with the values reported in [5] for bismuth and antimony tellurides, deduced by the emf method in the 643—683 K range. 

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