Antimony , crystal

An isopleth is a line of constant composition such as hijk in Fig. 15.7. At h, the system is entirely liquid. As the system cools, solid antimony appears at i as the antimony crystallizes out, the saturated liquid becomes richer in lead, and the liquid composition moves along the curve ice. At j the solution has the eutectic composition e and is saturated with respect to lead also, so lead begins to precipitate. The temperature remains constant even though heat flows out since, in this condition, the system is invariant. The amount of liquid diminishes and the amounts of solid lead and antimony increase. Finally the liquid solidifies, and the temperature of the mixed solids decreases along the line jk. If the process is done in reverse, heating a mixture of solid lead and solid antimony from /c, the state point moves from k to j. At j, liquid forms having the composition e. Note that the liquid formed has a different composition than the solid mixture. The system is invariant, so the... 

The best material system available at this time to meet the above criteria is the bismuth-antimony crystal system [ ]. In pure bismuth, the conduction and valence bands are slightly overlapped and, in the proper orientation, both holes and electrons have high and reasonably equal mobilities. The addition of a small amount of antimony has the effect of greatly reducing the lattice thermal conductivity. However, the addition of antimony also has the effect of decreasing the overlap of the principal conduction and valence bands in fact, for antimony concentrations greater than 5 atomic %, a gap exists and the system becomes a semiconductor, which is undesirable for these purposes [ ]. At present it appears that the optimum antimony content is about 3 atomic %. 

Add 5 g. of potassium hydrogen tartrate and 5 g. of antimony trioxide (each being finely powdered) to 30 ml. of water contained in a small flask, and boil the mixture under a reflux water-condenser for 15 minutes. Then filter hot, using a Buchner funnel and flask which have been preheated by the filtration of some boiling distilled water. Pour the clear filtrate into a beaker and allow to cool. Potassium antimonyl tartrate separates as colourless crystals. Filter, drain and dry. Yield, 5 g. The product can be recrystallised from hot water, but this is usually not necessary. 

For the production of tartar emetic (antimony potassium tartrate [28300-74-5]), potassium bitartrate [868-14 ] and antimony oxide, Sb202, are added simultaneously to water in a stainless-steel reactor. The reaction mixture is diluted, filtered, and collected in jacketed granulators where crystallization takes place after cooling. Centrihiging, washing, and drying complete the process. 

Tin exists in two ahotropic forms white tin (P) and gray tin (a). White tin, the form which is most familiar, crystallizes in the body-centered tetragonal system. Gray tin has a diamond cubic stmcture and may be formed when very high purity tin is exposed to temperatures well below zero. The ahotropic transformation is retarded if the tin contains smah amounts of bismuth, antimony, or lead. The spontaneous appearance of gray tin is a rare occurrence because the initiation of transformation requires, in some cases, years of exposure at —40° C. Inoculation with a-tin particles accelerates the transformation. 

The lead-base babbitts ate based upon the lead—antimony—tin system, and, like the tin-base, have a stmcture of hard crystals ia a relatively soft matrix. The lead-base ahoys ate, however, mote prone to segregation, have a lower thermal conductivity than the tin-base babbitts, and ate employed genetahy as an iaexpensive substitute for the tin-base ahoys. Properly lined, however, they function satisfactorily as beatings under moderate conditions of load and speed. 

Antimony is also used as a dopant in n-ty e semiconductors. It is a common additive in dopants for siHcon crystals with impurities, to alter the electrical conductivity. Interesting semiconductor properties have been reported for cadmium antimonide [12050-27-0] CdSb, and zinc antimonide [12039-35-9] ZnSb. The latter has good thermoelectric properties. Antimony with a purity as low as 99.9+% is an important alloying ingredient in the bismuth teUuride [1304-82-17, Bi Te, class of alloys which are used for thermoelectric cooling. 

Antimony Trioxide. Antimony(III) oxide (antimony sesquioxide) [1309-64-4] Sb203, is dimorphic, existing in an orthorhombic modification valentinite [1317-98-2] is colorless (sp gr 5.67) and exists in a cubic form and senarmontite [12412-52-17, Sb O, is also colorless (sp gr 5.2). The cubic modification is stable at temperatures below 570°C and consists of discrete Sb O molecules. The molecule is similar to that of P40 and As O and consists of a bowed tetrahedron having antimony atoms at each corner united by oxygen atoms lying in front of the edges. This solid crystallizes in a diamond lattice with an Sb O molecule at each carbon position. 

Antimony(III) iodide [7790-44-5] Sbl, forms red rhombohedral crystals, intermediate in stmcture between a molecular and an ionic crystal. In Sbl vapor there is no indication of association. 

Antimony Trisulfide. Antimony(III) sulfide (antimony sesquisulftde) [1345-04-6] SbS, exists as a black crystalline soHd, stibnite [1317-86-8] and as an amorphous red to yeUow-orange powder. Stibnite melts at 550°C and has Ai i° 298 175 kJ/mol (—41.8 kcal/mol)) A°29g, 182 J/(182 mol-K) [43.5 cal/(43.5 mol-K)] for the amorphous soHd AH° 298 1 147 kJ/mol (—35.1 kcal/mol) (38). The crystal stmcture of stibnite contains two distiucdy different antimony sites and consists of two parallel Sb S chains that are linked together to form cmmpled sheets (two per unit cell). 

Titanate Pigments. When a nickel salt and antimony oxide are calcined with mtile titanium dioxide at just below 1000°C, some of the added metals diffuse into the titanium dioxide crystal lattice and a yellow color results. In a similar manner, a buff may be produced with chromium and antimony a green, with cobalt and nickel and a blue, with cobalt and aluminum. These pigments are relatively weak but have extreme heat resistance and outdoor weatherabihty, eg, the yellow is used where a light cadmium could not be considered. They are compatible with most resins. 

Figure 7.6. A filled. skutterudite antimonide crystal structure. A transition niclal atom (Fc or Co) at the centre of each octahedron is bonded to antimony atoms at each corner. The rare earth atoms (small spheres) are located in cages made by eight octahedra. The large thermal motion of rattling of the rare earth atoms in their cages is believed be responsible for the strikingly low thermal conductivity of these materials (Sales 1997).

Tinplate and Solder. Metallurgical studies were performed to determine the effect of irradiation at low temperature on the corrosion resistance of tinplate and on the mechanical properties and microstructure of tinplate and side-seam solder of the tinplate container. The area of major interest was the effect of low-temperature irradiation on the possible conversion of the tin from the beta form to the alpha form. In the case of pure tin, the transition occurs at 18 °C. It was feared that low-temperature irradiation would create dislocations in the crystal lattice of tin and enhance the conversion of tin from the silvery form to a powdery form rendering the tin coating ineffective in protecting the base steel. Tin used for industrial consumption contains trace amounts of soluble impurities of lead and antimony to retard this conversion for several years. 

Especially notable is also the synthesis and structural characterization of an unusual antimony(III) guanidinate. 1,2,3-Tiiisopropylguanidine, Pr N = C(NHPr )2,was found to react with 1 molar equivalent of Sb(NMe2)3 in toluene under formation of a yellow solution, from which the novel compound Sb[Pr NC(NPr )2][Pr NHC(NPr )2] could be isolated in 10% yield as highly air-sensitive crystals. In the solid state, the complex adopts a heavily distorted trigonal-bipyramidal molecular structure in which the Sb is chelated by a [CfNPr ls] dianion and a [Pr NHC(NPr )2] monoanion (Figure 16). Supramolecular... 

The chalcogenide halides of antimony and bismuth are stable in air, and do not dissolve in H O or diluted acids. Their colors, mainly referring to single-crystal needles, are given in Tables XXIII and XXIV. 

XII. Antimony Of various new papers on the crystal growth of SbSI, the one by Ishikawa et al. (425) is worth mentioning, since it describes a new device especially designed to avoid formation of hollows in vapor-grown crystals. 

The ECALE synthesis of V-VI (V Sb, Bi) compounds has been attempted in a few works. Antimony telluride, Sb2Te3, nanofilms with a homogeneous microstructure and an average size of about 20 nm were formed epitaxially on a Pt substrate [61]. The optical band gap of these films was blue-shifted in comparison with that of the bulk single-crystal Sb2Tc3 compound. 

Given the strontium chloride crystal, write the defect reaction(s) expected if lithium chloride is present as an impurity. Do likewise for the antimony chloride impurity. Also, write the defeet reactions expected if both impurities are present in equal quantities. 

The potassium/caesium phase diagram is an example of a system involving the formation of mixed crystals with a temperature minimum (Fig. 4.4). The right and left halves of the diagram are of the same type as the diagram for antimony/bismuth. The minimum corresponds to a special point for which the compositions of the solid and the liquid are the same. Other systems can have the special point at a temperature maximum. 

This bismuth-III structure is also observed for antimony from 10 to 28 GPa and for bismuth from 2.8 to 8 GPa. At even higher pressures antimony and bismuth adopt the body-centered cubic packing of spheres which is typical for metals. Bi-III has a peculiar incommensurate composite crystal structure. It can be described by two intergrown partial structures that are not compatible metrically with one another (Fig. 11.11). The partial structure 1 consists of square antiprisms which share faces along c and which are connected by tetrahedral building blocks. The partial structure 2 forms linear chains of atoms that run along c in the midst of the square antiprisms. In addition, to compensate for the... 

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