Measurement of the Seebeck coefficients of binary Cu–Ni alloys

In order to identify materials suitable as a compensating wire pair for the Pt/Pd thermocouple, binary Cu(100-x)Ni(x) (x = 3, 5, 8 and 10 wt%) alloys were prepared and their Seebeck coefficients were measured using the temperature gradient method from room temperature to approximately 120 deg C using a pure platinum reference material. The Cu-Ni alloys showed negative Seebeck coefficients at all test temperatures. As the temperature increased, the Seebeck coefficients of the Cu-Ni alloys became more negative. At a fixed temperature, the Seebeck coefficients became more negative as the Ni content increased. Among the test alloys, Cu95Ni5 and Cu90Ni10 (designated as CuNi5/10) both showed a calculated thermal emf value that was very similar to that of the Pt/Pd thermocouple. It was concluded that the CuNi5/10 system could be a good compensating material for the Pt/Pd thermocouple, and by a small adjustment of the Ni content the temperature error could be reduced even further.