A study on thermoelectrical, structural and microstructural properties of Sb2Te3 and Bi2Te3 semiconductive alloys

A STUDY ON THERMOELECTRICAL, STRUCTURAL and MICROSTRUCTURALPROPERTIES of Sb2Te3 and Bi2Te3 SEMI CONDUCTIVE ALLOYSEmek MÖRÖYDOR DERUNChemical Engineering, Ph.D. ThesisThermoelectrical coolers with n-type and p-type semi-conductive metals as an alternative toclassical cooling systems are formed from thermoelectrical models . Cooling is done bypassing current through the modules. The increase of cooling yield changes due to thestructural characteristics of semi-conductive metals inside the modules .Nowadays compressors condensers and cooling fluids (CFC) are used in modern coolers.Direct current power supplies, semi-conductive materials and cooling blocks took their placesin thermoelectrical coolers (semi-conductor coolers) that are called as solid phase coolers.These materials don?t include harmfull fluids as CFC (Clor,flor,carbon). They are so reliablethat they don?t need repairement and caring and also they are friendly with environment andalso safe. When these advantages are analysed, production of thermoelectrical materials thatare called as semi-conductive metals, get more importantThe thermoelectrical coolers also provides confidence and rapid cooling. They are alsosoundless, anticorrosive and don?t include CFC which is used in refrigirators and harmfull tothe atmosphere so they are friendly with the environment.In this study production of battary for using in thermoelectrical coolers is aimed. First of alleutectic characteristics of thermoelements which will be used in battaries are examined andthey are determined.Bi-Te-Sb-Se thermoelements which are refined several times are used in the production of n-type Bi-Te-Se and p-type Bi-Te-Sb alloys with a good yield. After refinement of Bi2Te3,Sb2Te3 and Bi2Se3 semiconductive alloys are produced with crystal growth system in vacuumatmosphere and at high temperatures and as additive Nd and Cd are used. Beforemanufacturing of battary from the produced alloys, Differantial Thermal Analysis-Thermogravimetry (DTA-TG), Scanning Electron Microscope (SEM) and X-RayDiffractometry analysis of the alloys are confirmed. Then thermoelectrical measurements ofalloys are done and thermobattary is produced from alloys of p-type [%75 moleSb2Te3+%25 mole Bi2Te3] ve n-tipi [%96 mole Bi2Te3 + %4 mole Bi2Se3]. Yield, power thatis used and cost of the produced battary are calculated.As a conclusion these high yield semiconductive alloys will obtain great advantages fromeconomical, environmental, energical and technological point of view, and also it will abolishour dependence on other countries.Keywords: Bi2 Se3 alloys, Bi2Te3 alloys, Sb2Te3 alloys, semi conductivity, thermoelectricalcoolersJURY:1. Prof. Dr. Sabriye PİŞKİN (Supervisor) Date: 30.06.20052. Prof. Dr. Esen BOLAT Page: 1533. Prof. Dr. Cemalettin YAMAN4. Prof. Dr. Neşet KADIRGAN5. Prof. Dr. Ülker BEKER