| YBa2Cu3O7-?is a high-temperature superconducting oxide with a deformed perovskite structure(Tc?90 K,?=0?0.2).In the normal(metallic)state at room temperature of YBa2Cu3O7-?,the conductive Cu O2 layer and weakly conductive layers(Ba O,Cu O and Y layers)are stacked alternately along the c-axis tilted direction,thus forming significant transport anisotropy and atomic layer thermopile(ALTP)characteristics.Therefore we had designed a special artificial structure,that is to grow c-axis tilted epitaxial films on the vicinal cut single crystal substrates.Under the irradiation of light/heat source,the photothermal induced transverse voltage is generated,which can realize photothermal detection.In this paper,the high-temperature superconducting YBa2Cu3O7-?/Sr Ti O3(001)epitaxial films with c-axis tilt(0°-20°)were prepared.The photothermal induced transverse voltage effect and mechanism of the films under different wavelength pulse laser,high temperature black body and xenon lamp mercury light/heat irradiation were studied systematically.On this basis,the ALTP passive heat flux sensor prototypes were made using YBa2Cu3O7-?tilted epitaxial films as the core sensitive elements and used for static heat flow calibration.The high-temperature superconducting YBa2Cu3O7-?polycrystalline target with high crystal quality were prepared by solid state reaction after secondary sintering of900?/12h+950?/15h.The superconducting transition temperature Tc of the sample was 90.6K,and the Seebeck coefficient reached 9.64?V/K at 300 K.The YBa2Cu3O7-?epitaxial films with different thickness(deposition pulse number:2000 P,4000 P,6000 P,8000 P,10000 P,12000 P)were grown on Sr Ti O3(001)single crystal substrates with different tilted angle(0°,5°,10°,15°,20°)by pulse laser deposition(PLD).The deposition process was 750?800?/O2:40 Pa/350 m J/3Hz,and the annealing process was500?/O2:1×105Pa/1h.The results of XRD and phi-scan on YBCO(103)plane show that the film on flat substrate is a single c-axis oriented orthogonal phase with strict c-axis epitaxy and quadric symmetry.?and 2?scan were carried out on the 0°-15°inclined substrate,it was found that the c-axis angle difference between the films and the substrate was???0.54°,and the films maintained the c-axis epitaxy.Through AFM observation of films with different inclined angles,it was inferred that the epitaxial films show Stranski-Krastanov growth mode on flat substrates,while conform to Step-flow growth mode on vicinal cut substrates.The resistivity-temperature curve of 0°-15°/4000 P/YBa2Cu3O7-?/Sr Ti O3(001)epitaxial films in 70 K-280 K indicates that the superconducting critical transition temperature Tc of the films are 81-85.3 K,and the resistivity increases significantly with the increase of the tilt angle,it is mainly due to the greater?cof the material in the c-axis direction contributing to the tilt direction,as well as the stepped structure of the inclined film increases the unevenness of defects and interface scattering relative to the flat film.The LITV signal response rates of YBCO/Sr Ti O3(001)films(5°/2000 P,5°/4000 P,10°/4000 P)irradiated with different wavelengths(410-2400 nm)were measured.The response rate decreases with the increase of irradiation wavelength.In the range of 410-800 nm,the decrease was significant,while in the range of 900-2400 nm,the decrease was gentle.The turning point 800-900 nm corresponds to a photon energy of 1.38-1.15 e V,which is very close to the YBCO indirect band gap(1.3 e V).The response rate at 410-800 nm is strongly dependent on the wavelength of the irradiated light,indicating that there is a contribution to the photoconductive effect intrinsically related to the band gap of the material in the LITV signal.At 900-2400 nm,it belongs to the near-infrared region,and the photon energy is low,which has significant thermal effect.The LITV of the film is mainly based on the contribution of the transverse thermoelectric effect of the material intrinsic thermal potential anisotropy?S.As the film thickness increases(2000 P?4000 P),the response rate increases.The thermal detection of 5°and 10°/4000 P/YBCO/Sr Ti O3(001)films irradiated by xenon lamp(800-1000 nm)and high-pressure mercury lamp(320-750 nm)was researched.The response voltage has a linear relationship with the irradiation power density.The response rate under xenon lamp is 180?Vcm2/W,and that under high-pressure mercury lamp is slightly higher than xenon lamps?230?Vcm2/W,which which can also be attributed to the contribution of photoconductivity.The detection element of heat flow sensor based on YBCO/Sr Ti O3(001)ALTP film was explored,and the response rate was calibrated under high temperature black body radiation.The sensitivity of ALTP heat flux sensor is up to 104.91-220.91?Vcm2/W,which the maximum exceeds the water-cooling Gardon gauge(180.25?Vcm2/W),and is 2 times larger than the only ALTP device(69?Vcm2/W)with the same working principle reported by German.The device prototypes show good linear relationship between heat flow energy densities and signal voltages,the linear correlation coefficient R-square?0.99.There are good repeatabilities and performances. |
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