The heat flux sensors composed of inclined epitaxial La_1−xCa_xMnO₃ (LCMO) films have been fabricated on c-axis miscut SrTiO₃ (001) single crystal substrates. Based on the transverse thermoelectric (TTE) effect originated from the anisotropic Seebeck coefficient between ab-plane and c-axis of LCMO films, the obvious response voltages perpendicular to the temperature gradient are detected, and their amplitudes show good linearity with heat fluxes. The sensitivities of heat flux sensors are 8.64, 11.88, 12.66, and 14.25 μV/(kW/m²) for LCMO films with inclined 12°, 18°, 20°, and 24°, respectively. Additionally, the response frequency of the sensor reaches ∼300 kHz at −3 dB, which is comparable with the reported TTE heat flux sensors composed of YBa₂Cu₃O_7-δ. The above results demonstrate the potential of the LCMO-based TTE heat flux sensors in high-frequency heat flux measurement.

Accurately monitoring heat flux distribution can enhance the service stability of aeroengine hot-end components. The extreme environmental temperature and fast heat transfer between high-speed load and hot components propose serious requirements for heat flux sensors, including high-temperature resistance and fast response. This article fabricates the fast response thin film heat flux sensor based on the transverse thermoelectric (TTE) effect of La _1-x Ca _x MnO ₃ (LCMO). The TTE heat flux sensor shows excellent high-temperature resistance at 1000°C. After high-temperature heat treatment for 1 h, the performance of the sensor is improved due to the optimization of the crystal quality and biaxial texture of the LCMO thin film, as well as the reduction of resistance. The sensitivity increases from 7.39 μV/(kW/m ² ) to 7.79 μV/(kW/m ² ), and the response time reduces from 58 ns to 42 ns. Then, the performance of the thin film heat flux sensor shows little changes after completing high-temperature heat treatment for up to 7 hours at 1000°C. The TTE heat flux sensor can show a satisfied response in a high-temperature environment at 1000°C, with a sensitivity of 1.18 μV/(kW/m ² ) without the consideration of laser absorption. The TTE heat flux sensor exhibits stable high-temperature resistance at 1000°C and can operate normally at 1000°C, indicating its potential in fast heat flux measurement for harsh environments.

The atomic layer thermopile (ALTP) heat flux sensor has played an important role in the study of boundary layer transition. However, the response characteristics of the sensors still have not yet been clarified sufficiently. Herein, the angle- and thickness-dependent response characteristics of the ALTP heat flux sensors are investigated. Based on a one-dimensional thermal conductivity model, the anisotropic thermal conductivity ( K_ab =4.28 W/m·K, K_c =0.53 W/m·K) and anisotropic Seebeck coefficient (Δ S =16.72 μV/K) of YBCO thin films are obtained by fitting the angle-dependent sensitivities. As the inclined angle increases, the increased thermal conductivity K_z along the normal direction of the thin film leads to a decrease in temperature difference Δ T . Therefore, the sensitivity of the ALTP heat flux sensor only reaches the maximum value ~ 24.16 μV/(kW/m ² ) at 18° even if the inclined angle continues to increase. The increased thermal conductivity K_z results in a decrease in the response time of the ALTP heat flux sensor as the inclined angle increases. The results of static calibration experiments and simulations indicate that the sensitivity of the ALTP heat flux sensor is almost independent of the thickness of the thin film, but their response time gradually decreases with increasing thickness based on heat conduction theory. This work may provide a good design basis for the application of ALTP heat flux sensor.