Interfacial properties of Cu/Ni/Mg2Si joints prepared in one step by the spark plasma sintering method

Cu/Ni/Mg2Si thermoelectric bonded joints were prepared in one step by the spark plasma sintering (SPS) method using Mg and Si powders to form Mg2Si. The microstructure and elemental distribution across the interfaces were determined, and the formation of new phases at the interface was investigated and related to joint properties, including shear strength and contact resistance. Joint formation was accompanied by the formation of two ternary Mg-Si-Ni layers, an η-layer with Ni2Si as a precipitate next to Ni, and an ω-layer next to Mg2Si. The formation and characteristics of these layers played a major role in determining the shear strength and contact resistance. It was determined that a reactive sintering temperatures in the range 1023-1053 K with a 15-20 min hold time provided the best properties. The maximum shear strength of the joints obtained is 26 MPa for samples sintered at 1023 K. For these samples the contact resistance was 1.44 mΩ cm2; the minimum value of 1.28 mΩ cm2 was measured for samples sintered at 1073 K. Long-term thermal stability of joints was also investigated.