8409

7789

كارشناسي ارشد

فيزيك

اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك

1392

نه،99ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

فيزيك

ID7789

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

AbstractOne of the main challenges of the modern world is finding new sources of energy Nowadays thermoelectric materials which directly convert heat into electricity are considered as possiblenovel energy sources that can also be effective in reducing global warming The closestpromising thermoelectric application seems to happen in the automobile industry GeneralMotors has stated that only 10 percent reduction of fuel consumption in this company sautomobiles will save 100 million gallons of fuel per year for America The main deficiency of the conventioned thermoelectric materials is their low efficiency whichperivents them to compete with the conventional heating and cooling systems Hence scientistsare using nanotechnology to look for new thermoelectric materials which have high powerefficiency Superlattices are two dimensional nano systems which seem to be promising forimproving figure of merit of thermoelectric materials Hence in this research we studythermoelectric properties of AgSbSe2 n AgSbTe2 n n 1 2 thin film superlattices Ternarychalcogenides AgSbQ2 Q S Se Te are thermoelectric materials with high seebeck effect andelectrical conductivity and low thermal conductivity and consequantly high thermoelectricperformance In this project structural electronic and transport properties of AgSbSe2 AgSbTe2 and AgSbSe2 n AgSbTe2 n thin film superlattices have been calculated in the framework within the density functional theory and pseudopotential formalism Within the GGAapproximation AgSbSe2 and AgSbTe2 are predicted to be semimetals whereas these materialsare narrow band gap semiconductors To solve the gap problem we used GGA U and spin orbit interaction Spin orbit interaction could not open any gap in the systems while GGA Ucould estimate the band gap of AgSbSe2 In the next step we calculated transport properties ofthese alloys Then after constructing the superlattices n 1 2 we calculated transport properties by usingthe scissor corrected and the GGA U electronic structures of the systems Our results show AgSbSe2 1 AgSbTe2 1 superlattice exhibits improved thermoelectric properties comparedwith the alloys and AgSbSe2 2 AgSbTe2 2 superlattice and a high figure of merit is speculatedfor this system Keywords first principles calculations AgSbSe2 AgSbTe2 superlattice seebeck coefficient powerfactor electrical conductivity figure of merit GGA U spin orbit

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