Optimization of Chemical and Electrochemical Methods of Metal Deposition on Thermoelectric Materials

Methods of obtaining contacts to thermoelectric materials based on Bi₂Te_2.8Se_0.2 and Bi_0.5Sb_1.5Te₃ by chemical and electrochemical deposition of nickel, up to 20 μm thick, have been optimized. Using a galvanostatic mode in an electrolyte containing: NiSO₄×7H₂O; NaCl; H₃BO₃, the rest is water, at a current density of 1 A/dm², nickel contacts with an adhesion strength of 8.70 to 10.66 MPa were obtained. The maximum adhesion strength was obtained for contact layers with a thickness of 8 microns formed by chemical deposition of Ni on the legs of thermoelements with a pre-deposited Ni layer 300 nm thick. Chemical deposition of Ni was carried out in a borohydride electrolyte containing: NiSO₄×7H₂O; KNaC₄H₄O₆×4H₂O; NaOH; C₂H₅NO₂; K₂Cr₂O₇; NaBH₄ at a temperature of 80-90°C. The adhesion strength of the obtained nickel contacts is 15.87-16.56 MPa. The specific contact resistance for optimized contact formation methods ranges from 1.0 to 2.0*10^-9 Ohm*m².