Miniaturized heat-flux sensor based on a glass-insulated Bi–Sn microwire

Thermoelectric-energy conversion based on a single element made of an anisotropic material is considered. In such materials, the heat flux generates a transverse electric field. We fabricate an experimental heat-flux sensor (HFS) sample consisting of a 10-m-long glass-insulated single-crystal tin-doped bismuth microwire (outer diameter $D$ = 18 $\mu$m, microwire diameter $d$ = 4 $\mu$m). The microwire is wound into a flat spiral after recrystallization in a strong electric field, during which the main crystallographic axis $C_3$ is oriented at the optimum angle with respect to the microwire axis. The sensor sensitivity reaches 10$^{-2}$ V/W with the time constant $\tau\approx$ 0.2 s. The sensor fabrication technology is rather simple and reliable for industrial applications.