Thermoelectric and various kinds of modules require joining processes at higher temperatures. Both the Ag-Sb eutectic, Ag-41.0at.%Sb and Ag-Cu eutectic, Ag-39.9at.%Cu are good braze candidates. Co and Ni are frequently used as barrier layer materials. The interfacial reactions in the Co/Ag-Cu, Ni/Ag-Cu, Co/Ag-Sb and Ni/Ag-Sb are examined to provide fundamental understanding if Ag-Cu and Ag-Sb braze alloys are used. The related phase diagrams, Ag-Co-Ni, Ag-Co-Sb, Ag-Cu-Sb and Ag-Cu-Sb, are assessed and the interfacial reaction results are illustrated thereupon. No ternary compounds are observed in all the related ternary systems. Two phases, Ni5Sb2 and NiSb, are formed in the Ni/Ag-41.0at%Sb couples at 550℃. The Ni5Sb2 phase grows very fast. Two phases, CoSb and CoSb3, are formed in the Co/Ag-41.0at%Sb couples reacted at 550oC. The CoSb3 phase grows much faster than CoSb. No compound is formed in the Ni/Ag-39.9at%.Cu couples. The reaction layer is a layer of (Cu,Ni) solution of Ag solubility.