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Lead tin telluride, also referred to as PbSnTe or Pb1-xSnxTe, is a ternary alloy of lead, tin and tellurium, generally made by alloying either tin into lead telluride or lead into tin telluride. It is a IV-VI narrow band gap semiconductor material. The band gap of Pb1-xSnxTe is tuned by varying the composition(x) in the material. SnTe can be alloyed with Pb (or PbTe with Sn) in order to tune the band gap from 0.29 eV (PbTe) to 0.18 eV (SnTe). It is important to note that unlike II-VI chalcogenides, e.g. cadmium, mercury and zinc chalcogenides, the band gap in Pb1-xSnxTe does not changes linearly between the two extremes. In contrast, as the composition (x) is increased, the band gap decreases, approaches zero in the concentration regime (0.32-0.65 corresponding to temperature 4-300 K respectively) and further increases towards bulk band gap of SnTe. Therefore, the lead tin telluride alloys have narrower band gaps than their end point counterparts making lead tin telluride an ideal candidate for mid infrared, 3-14 μm opto-electronic application. ==Properties== Lead tin telluride is p-type semiconductor at 300K. The hole concentration increases as the tin content is increased resulting in an increase in electrical conductivity. For composition range x= 0 to 0.1, electrical conductivity decreases with increase in temperature upto 500K and increases beyond 500K. For composition range, x≥0.25, electrical conductivity decreases with increases in temperature. The Seebeck coefficient of Pb1-xSnxTe decreases with increases in Sn content at 300K. For composition x> 0.25, thermal conductivity of Pb1-xSnxTe increases with increase in Sn content. Thermal conductivity values decreases with increase in temperature over the entire composition range, x>0. For Pb1-xSnxTe, the optimum temperature corresponding to maximum power factor increases with increase in composition x.The pseudo binary alloy of Lead tin telluride acts as a thermoelectric material over 400-700K temperature range.〔Orihashi, M.; Noda, Y.; Chen, L. D.; Goto, T.; Hirai, T., Effect of tin content on thermoelectric properties of p-type lead tin telluride. Journal of Physics and Chemistry of Solids 2000, 61 (6), 919-923.〕 Lead tin telluride has a positive temperature coefficient i.e for a given composition x, band gap increases with temperature. Therefore, temperature stability has to be maintained while working with lead tin telluride based laser. However, the advantage is that the operating wavelength of the laser can simply be tuned by varying the operating temperature. The optical absorption coefficient of lead tin telluride is typically ~750 cm−1 as compared to ~50−1 for the extrinsic semiconductors e.g. doped Silicon.〔E. Burstein, G. Picus, and N. Sciar, "Optical and Photoconductive Properties of Silicon and Germanium," Photoconductivity Conference, R. G. Breckenridge, Ed., pp. 353 -409, John Wiley & Sons, Inc., New York, 1954.〕 The higher optical coefficient value not only ensures higher sensitivity but also reduces the spacing required between individual detector elements to prevent optical cross talk making integrated circuit technology easily accessible.〔Mathur, D. P., Recent Infrared Detector Developments for Future Remote Sensor Applications. OPTICE 1975, 14 (4), 144351-144351〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lead tin telluride」の詳細全文を読む スポンサード リンク
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