Ni/Te and Ni/Ag2Te interfacial reactions

Ag2Te is a promising thermoelectric compound, and Ni is commonly used as a barrier layer. The interfacial reactions in the Ni/Te and Ni/Ag2Te couples are examined at 200 °C and 250 °C. To illustrate the reaction paths in the Ni/Ag2Te couples, the AgNiTe isothermal sections at 200 °C and 250 °C are determined based on experimental results of this study and related phase equilibria information. There is no ternary compound phase found and the phase relationships are same at 200 °C and 250 °C. The reaction paths of the two reaction couples are identical at these two temperatures. Three intermediate phases, Ni3Te2, NiTe0.775 and NiTe2, are formed in the Ni/Te couples. The reaction rate increases significantly at 250 °C, and is about six times higher than that at 200 °C. Only the Ni3Te2 and Ag phases are observed in the Ni/Ag2Te couples. The reaction path is Ag2Te/Ni3Te2/Ag/Ni in the Ni/Ag2Te couples at both 200 °C and 250 °C.