Study On Preparation Of Doped STO Heat Flux Sensitive Thin Film

The Atomic Layer Thermopile（ALTP）heat flux sensor has important applications in the aerospace field due to its simple structure and fast response.However,for applications such as the aero-engine hot-end components and the surfaces of high-speed aircraft,the heat flux sensor is required to operate stably in high-temperature environments with a high response output.Therefore,it is of significant to develop high-temperature ALTP heat flux sensor with high sensitivity coefficient and fast response for practice application.Herein,this thesis focuses on the preparation of Sr Ti O₃-based films and their performance controlling,as detailed below:The preparation process parameters of the Nb-doped Sr Ti O₃（STNO）heat flux sensitive thin films were explored.Using the target with the mass ratio of Nb:5%,the effects of the substrate temperature,sputtering Ar pressure,and radio frequency（RF）power on the STNO film were investigated using RF magnetron sputtering.The STNO film had a single growth orientation,good biaxial texture,a dense and low-roughness surface,a uniform element distribution in the film.The performance of STNO film is below:resistivity of 12.3Ω·cm,LITV signal amplitude of 6.8 V,and the response time of 2.7μs.The preparation process parameters of the La-doped Sr Ti O₃（LSTO）heat flux sensitive thin films were explored based on the MOCVD system.The effects of oxygen partial pressure,substrate temperature,and La doping amount on the structure and LITV performance of the LSTO film were systematically studied.The epitaxial La_0.2Sr_0.8Ti O₃film had a single growth orientation,good biaxial texture（Δω=0.25°,Δφ=0.47°）,and a step-like morphology on the film surface based on the optimized process parameters including the oxygen flow rate of 1280 ml/min and the substrate temperature of 830℃.Compared with STNO film,the resistivity of LSTO film reduced to 0.03Ω·cm,and then LITV signal amplitude increased to 23.3 V,the response time decreased to about 36 ns.The sensitivity calibration and high-temperature performance testing of the LSTO heat flux sensitive thin film were conducted.The LSTO film with effective length of 5mm was calibrated using a comparative method.The potential outputs of the LSTO film had a highly linear relationship with the heat fluxes,and the sensitivity coefficient was22.29μV/（k W/m²）by linear fitting.The high-temperature performance testing of LSTO heat flux sensitive thin film was performed form room temperature to 500℃,and its LITV performance decreased as the temperature increased.At 500℃,the LITV signal amplitude of the LSTO film decreased to 14.5%of that at room temperature,and the response time increased to 3.89 times of that at room temperature.The preparation of the LSTO heat flux sensitive thin film based on a flexible metal base was explored.The epitaxial film had a single growth orientation and good conductivity performance.The minimumΔωandΔφwere 1.8°and 6.2°,respectively.This laid the foundation for the preparation of LSTO doped heat flux sensitive thin film on inclined functional layers of flexible substrates.