Thermal Conductivity of Platinum Microwire by 3ω Method

The thermal conductivity (K) of platinum microwires at 300 and 400 K has been determined by the 3 omega method. In this technique, a sample is heated by driving a sinusoidal current at an angular frequency omega, which causes a temperature and resistance fluctuation at an angular frequency of 2 omega, leading to a voltage signal at 3 omega. Four electrodes were attached to the microwire samples along its length and a sinusoidal voltage source (at 1 omega) was used to pass a current through the outer two electrodes while the 3 omega voltage was measured across the inner two probes. A vacuum of similar to 10(-5) torr was maintained inside the sample chamber and the measurement was done at 300 K and 400 K. In order to minimize radiation loss, the sample was shielded by heated reflective inner copper and outer stainless steel heat-shields. In-phase and out-of-phase 3 omega voltages were measured with a digital lock-in amplifier and the data were fit by adjusting the value of the thermal resistance, which is a function of K. The density and specific heat capacity of platinum, which were parameters, required in the fitting of the experimental data to theoretical projections, were obtained from the literature. The measured values of the thermal conductivity of platinum microwire at temperatures of 300 K and 400 K were determined to be 71.8 Wm(-1)K(-1) and 73.3 Wm(-1)K(-1) respectively.