Investigations On The Electrodeposition Mechanisms And Preparation Technology Of P-type Bi_xSb_2-xTe₃ Thermoelectric Films In H₂SO₄ Bath

In recent years,with the deepening energy crisis and the increasing environmental pollution,the demand for clean energy is more and more pressing,Thermoelectric generators can convert heat to electricity.The process is emission-free and the battery has well performances and long life,which make it a promising green energy.Thermoelectric genera tors functions depended on the Seebeck effect.In a large number of thermoelectric materials,Bi2 Te3 based thermoelectric materials has excellent properties,thus becomes the research focus.The electrodeposition mechanism of three elements,BiIII,SbIII TeIV,were studied using the test methods of Cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)in the sulfuric acid system.On this basis,further experiments were conducted to investigate the effects of the concentrations of Na2 EDTA,tartaric acid,sulfuric acid and potassium nitrate on the p type Bix Sb2-x Te3 film material deposition process in sulfuric acid system.So the component ratio of the solution can be determined.Then the micro-morphology,composition and thermoelectric properties of the p type Bix Sb2-x Te3 ternary thermoelectric materials obtained at various deposition parameters such as substrate material,deposition potential,flow rate,temperature and supplement technique,were analysized by the means of spectrum test instrument(EDS),stereomicroscope,Resistivity Tester as well as Seebeck Tester.After that,the optimized preparation technology could be obtained.Experimental results show that the electrochemical deposition processes of BiIII SbIII TeIV are all carried out in steps in sulfuric acid system and the redox processes of these three elements are irreversible.In addition,complexing agents not only greatly have enhanced the solubility of three elements,improved the stability of mixed,but also have made the deposition potentials of three elements close to each other,which is favorable for the p type Bix Sb2-x Te3 thin film deposition.During the deposition process,the deposition techniques of the p type Bix Sb2-x Te3 thin film has been optimized by changing the co ncentration of the complexing agents,sulfuric acid,and conductive salt.Regulating deposition potential for-0.145 V,flow rate for medium speed,and test temperature for 23 ?,the morphology and thermoelectric properties of the thin film have reached the optimal level.Seebeck coefficient is 158 ?V?K-1,resistance is 1.14×10-5 ?·m-1,power factor is 2.19 mW/(K2m).Besides,supplement techniques,which may increase the solution life and maintain the components of the thin film,has effectively enhanced the performances of the p type Bix Sb2-x Te3 materials.